Pneumonia

Definition

Pneumonia is an infection of the lung that can be caused by nearly any class of organism known to cause human infections . These include bacteria, amoebae, viruses, fungi, and parasites. In the United States, pneumonia is the sixth most common disease leading to death; 2 million Americans develop pneumonia each year, and 40,000–70,000 die from it. Pneumonia is also the most common fatal infection acquired by already hospitalized patients. In developing countries, pneumonia ties with diarrhea as the most common cause of death. Even in nonfatal cases, pneumonia is a significant economic burden on the health care system. One study estimates that people in the American workforce who develop pneumonia cost employers five times as much in health care as the average worker.

According to the Centers for Disease Control and Prevention (CDC), however, the number of deaths from pneumonia in the United States has declined slightly since 2001.

Description

Anatomy of the lung

To better understand pneumonia, it is important to understand the basic anatomic features of the respiratory system. The human respiratory system begins at the nose and mouth, where air is breathed in (inspired) and out (expired). The air tube extending from the nose is called the nasopharynx. The tube carrying air breathed in through the mouth is called the oropharynx. The nasopharynx and the oropharynx merge into the larynx. The oropharynx also carries swallowed substances, including food, water, and salivary secretion that must pass into the esophagus and then the stomach. The larynx is protected by a trap door called the epiglottis. The epiglottis prevents substances that have been swallowed, as well as substances that have been regurgitated (thrown up), from heading down into the larynx and toward the lungs.

A useful method of picturing the respiratory system is to imagine an upside-down tree. The larynx flows into the trachea, which is the tree trunk, and thus the broadest part of the respiratory tree. The trachea divides into two tree limbs, the right and left bronchi. Each one of these branches off into multiple smaller bronchi, which course through the tissue of the lung. Each bronchus divides into tubes of smaller and smaller diameter, finally ending in the terminal bronchioles. The air sacs of the lung, in which oxygen-carbon dioxide exchange actually takes place, are clustered at the ends of the bronchioles like the leaves of a tree. They are called alveoli.

The tissue of the lung that serves only a supportive role for the bronchi, bronchioles, and alveoli is called the lung parenchyma.

Function of the respiratory system

The main function of the respiratory system is to provide oxygen, the most important energy source for

the body's cells. Inspired air (the air taken in when a person breathes) contains oxygen, and travels down the respiratory tree to the alveoli. The oxygen moves out of the alveoli and is sent into circulation throughout the body as part of the red blood cells. The oxygen in the inspired air is exchanged within the alveoli for the waste product of human metabolism, carbon dioxide. The air you breathe out contains the gas called carbon dioxide. This gas leaves the alveoli during expiration. To restate this exchange of gases simply, you breathe in oxygen, you breathe out carbon dioxide

Respiratory system defenses

The healthy human lung is sterile. There are normally no resident bacteria or viruses (unlike the upper respiratory system and parts of the gastrointestinal system, where bacteria dwell even in a healthy state). There are multiple safeguards along the path of the respiratory system. These are designed to keep serious, pathogenic organisms from invading, and leading to infection.

The first line of defense includes the hair in the nostrils, which serves as a filter for larger particles. The epiglottis is a trap door of sorts, designed to prevent food and other swallowed substances from entering the larynx and then trachea. Sneezing and coughing, both provoked by the presence of irritants within the respiratory system, help to clear such irritants from the respiratory tract.

Mucus produced by the respiratory system also serves to trap dust and infectious organisms. Tiny hair-like projections (cilia) from cells lining the respiratory tract beat constantly. They move debris trapped by mucus upwards and out of the respiratory tract. This mechanism of protection is referred to as the mucociliary escalator.

Cells lining the respiratory tract produce several types of immune substances that protect against various organisms. Other cells (called macrophages) along the respiratory tract actually ingest and kill invading organisms.

The organisms that cause pneumonia, then, are usually carefully kept from entering the lungs by virtue of these host defenses. However, when an individual encounters a large number of organisms at once, the usual defenses may be overwhelmed. Infection may happen either by inhaling contaminated air droplets, or by aspiration of organisms inhabiting the upper airways.

CONDITIONS PREDISPOSING TO PNEUMONIA. In addition to exposure to sufficient quantities of causative organisms, certain conditions may make an individual more likely to become ill with pneumonia. Certainly, the lack of normal anatomical structure could result in an increased risk of pneumonia. For example, there are certain inherited defects of cilia which result in less effective protection. Cigarette smoke, inhaled directly by a smoker or second-hand by an innocent bystander, interferes significantly with ciliary function, as well as inhibiting macrophage function.

Stroke , seizures, alcohol, and various drugs interfere with the function of the epiglottis. A weak epiglottis leads to a leaky seal on the trap door, with possible contamination by swallowed substances and/or regurgitated stomach contents. Alcohol and drugs also interfere with the normal cough reflex. This inteference further decreases the chance of clearing unwanted debris from the respiratory tract.

Viruses may interfere with ciliary function, allowing themselves or other microorganism invaders (such as bacteria) access to the lower respiratory tract. One of the most important viruses is HIV (Human Immunodeficiency Virus), the causative virus in AIDS (acquired immunodeficiency syndrome). In recent years this virus has resulted in a huge increase in the incidence of pneumonia. Because AIDS results in a general decreased effectiveness of many aspects of the host's immune system, a patient with AIDS is susceptible to all kinds of pneumonia. This includes some previously rare parasitic types that would be unable to cause illness in an individual possessing a normal immune system.

The elderly have a less effective mucociliary escalator, as well as changes in their immune system. This causes this age group to be more at risk for the development of pneumonia.

Various chronic conditions predispose a person to infection with pneumonia. These include asthma , cystic fibrosis, and neuromuscular diseases that may interfere with the seal of the epiglottis. Esophageal disorders may result in stomach contents passing upwards into the esophagus. This increases the risk of aspiration into the lungs of those stomach contents with their resident bacteria. Diabetes, sickle cell anemia , lymphoma, leukemia , and emphysema also predispose a person to pneumonia.

Genetic factors also appear to be involved in susceptibility to pneumonia. Certain changes in DNA appear to affect some patients' risk of developing such complications of pneumonia as septic shock.

Pneumonia is also one of the most frequent infectious complications of all types of surgery. Many drugs used during and after surgery may increase the risk of aspiration, impair the cough reflex, and cause a patient to underfill their lungs with air. Pain after surgery also discourages a patient from breathing deeply enough, and from coughing effectively.

Radiation treatment for breast cancer increases the risk of pneumonia in some patients by weakening lung tissue.

In addition, the use of mechanical ventilators to assist patients in breathing after surgery increases their risk of developing pneumonia. The mortality rate among ventilated patients who develop pneumonia is 46%.

Causes & symptoms

Causes

The list of organisms that can cause pneumonia is very large, and includes nearly every class of infectious organism: viruses, bacteria, bacteria-like organisms, fungi, and parasites (including certain worms ). Different organisms are more frequently encountered by different age groups. Further, other characteristics of an individual may place him or her at greater risk for infection by particular types of organisms:

• Viruses cause the majority of pneumonias in young children (especially respiratory syncytial virus, parainfluenza and influenza viruses, and adenovirus).
• Adults are more frequently infected with bacteria (such as Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus ).
• Pneumonia in older children and young adults is often caused by the bacteria-like Mycoplasma pneumoniae (the cause of what is often referred to as "walking" pneumonia).
• Pneumocystis carinii is an extremely important cause of pneumonia in patients with immune problems, such as patients being treated for cancer with chemotherapy, or patients with AIDS. Classically considered a parasite, it appears to be more related to fungi.
• People who have reason to come into contact with bird droppings, such as poultry workers, are at risk for pneumonia caused by the organism Chlamydia psittaci.
• A very large, serious outbreak of pneumonia occurred in 1976, when many people attending an American Legion convention were infected by a previously unknown organism. Subsequently named Legionella pneumophila, it causes what is now called "Legionnaire's Disease." The organism was traced to air conditioning units in the convention's hotel.

Symptoms

Pneumonia is suspected in any patient who has fever , cough, chest pain, shortness of breath, and increased respirations (number of breaths per minute). Fever with a shaking chill is even more suspicious. Many patients cough up clumps of sputum, commonly known as spit. These secretions are produced in the alveoli during an infection or other inflammatory condition. They may appear streaked with pus or blood. Severe pneumonia results in the signs of oxygen deprivation. This includes blue appearance of the nail beds or lips (cyanosis).

The invading organism causes symptoms, in part, by provoking an overly strong immune response in the lungs. In other words, the immune system that should help fight off infections, kicks into such high gear, that it damages the lung tissue and makes it more susceptible to infection. The small blood vessels in the lungs (capillaries) become leaky, and protein-rich fluid seeps into the alveoli. This results in less functional area for oxygen-carbon dioxide exchange. The patient becomes relatively oxygen deprived, while retaining potentially damaging carbon dioxide. The patient breathes faster and faster, in an effort to bring in more oxygen and blow off more carbon dioxide.

Mucus production is increased, and the leaky capillaries may tinge the mucus with blood. Mucus plugs actually further decrease the efficiency of gas exchange in the lung. The alveoli fill further with fluid and debris from the large number of white blood cells being produced to fight the infection.

Consolidation, a feature of bacterial pneumonias, occurs when the alveoli, which are normally hollow air spaces within the lung, instead become solid, due to quantities of fluid and debris.

Viral pneumonias and mycoplasma pneumonias do not result in consolidation. These types of pneumonia primarily infect the walls of the alveoli and the parenchyma of the lung.

Severe acute respiratory syndrome (SARS)

Severe acute respiratory syndrome, or SARS, is a contagious and potentially fatal disease that first appeared in the form of a multi-country outbreak in early February 2003. Later that month, the CDC began to work with the World Health Organization (WHO) to investigate the cause(s) of SARS and to develop guidelines for infection control. SARS has been described as an "atypical pneumonia of unknown etiology;" by the end of March 2003, the disease agent was identified as a previously unknown coronavirus.

The early symptoms of SARS include a high fever with chills, headache , muscle cramps, and weakness. This early phase is followed by respiratory symptoms, usually a dry cough and painful or difficult breathing. Some patients require mechanical ventilation. The mortality rate of SARS is thought to be about 3%.

As of the end of March 2003, the CDC did not have clearly defined recommendations for treating SARS. Treatments that have been used include antibiotics known to be effective against bacterial pneumonia; ribavirin and other antiviral drugs; and steroids.

Diagnosis

For the most part, diagnosis is based on the patient's report of symptoms, combined with examination of the chest. Listening with a stethoscope will reveal abnormal sounds, and tapping on the patient's back (which should yield a resonant sound due to air filling the alveoli) may instead yield a dull thump if the alveoli are filled with fluid and debris.

Laboratory diagnosis can be made of some bacterial pneumonias by staining sputum with special chemicals and looking at it under a microscope. Identification of the specific type of bacteria may require culturing the sputum (using the sputum sample to grow greater numbers of the bacteria in a lab dish.).

X-ray examination of the chest may reveal certain abnormal changes associated with pneumonia. Localized shadows obscuring areas of the lung may indicate a bacterial pneumonia, while streaky or patchy appearing changes in the x-ray picture may indicate viral or mycoplasma pneumonia. These changes on x ray, however, are known to lag in time behind the patient's actual symptoms.

Treatment

Pneumonia is a potentially serious condition that requires prompt medical attention. Patients should contact their doctors for immediate diagnosis and treatment. Alternative treatment such as nutritional support, however, can help alleviate some of the symptoms associated with pneumonia and boost the body's immune function.

Diet and nutrition

The following nutritional changes are recommended:

• Avoid all potentially allergenic foods, and determine allergenic foods with an elimination diet.
• Reduce intake of sugar and processed foods.
• Give yourself plenty of rest.
• Get plenty of fluids to prevent dehydration and help loosen phlegm.
• Nutritional supplements such as vitamins C, bioflavonoids, vitamin A , beta-carotene, and zinc may help.

Herbal treatment

Over-the-counter herbal preparations such as glycerol guaiacolate can help clear the lungs of phlegm and speed up the recovery process. Antimicrobial herbs, such as goldenseal (Hydrastis canadenis ) and Chinese herbs, which stimulate the immune system, may be taken for treatment.

Other treatment

Other treatments, such as yoga , help with breathing, movement, and relaxation . Also recommended is meditation and the use of guided imagery . Contact local practitioners to enroll in such therapies.

Allopathic treatment

Prior to the discovery of penicillin antibiotics, bacterial pneumonia was almost always fatal. Today, antibiotics, especially given early in the course of the disease, are very effective against bacterial causes of pneumonia. Erythromycin and tetracycline improve recovery time for symptoms of mycoplasma pneumonia. They do not, however, eradicate the organisms. Amantadine and acyclovir may be helpful against certain viral pneumonias.

A newer antibiotic named linezolid (Zyvox) is being used to treat penicillin-resistant organisms that cause pneumonia. Linezolid is the first of a new line of antibiotics known as oxazolidinones. Another new drug known as ertapenem (Invanz) is reported to be effective in treating bacterial pneumonia.

Expected results

Rate of recovery varies according to the type of organism causing the infection. Recovery following pneumonia with Mycoplasma pneumoniae is nearly 100%. Staphylococcus pneumoniae has a death rate of 30–40%. Similarly, infections with a number of gram negative bacteria (such as those in the gastrointestinal tract which can cause infection following aspiration) have a high death rate of 25–50%. Streptococcus pneumoniae, the most common organism causing pneumonia, produces a death rate of about 5%. More complications occur invery young or very old individuals who have multiple areas of the lung infected simultaneously. Individuals with other chronic illnesses (including cirrhosis of the liver, congestive heart failure, individuals without a functioning spleen, and individuals who have other diseases that result in a weakened immune system) experience complications. Patients with immune disorders, various types of cancer, transplant patients, and AIDS patients also experience complications.

Prevention

Because many bacterial pneumonias occur in patients who are first infected with the influenza virus, yearly vaccination against influenza can decrease the risk of pneumonia for the elderly and people with chronic diseases such as asthma, cystic fibrosis, diabetes, kidney disease and cancer.

Maintaining a healthy diet that includes whole foods and vitamin C and B-complex vitamins will aid in prevention. Also helpful in terms of both good health and prevention of pneumonia is developing a regular exercise regimen, as well as reducing stress .

A specific vaccine against Streptococcus pneumoniae is very protective, and should also be administered to patients with chronic illnesses.

Patients who have decreased immune resistance are at higher risk for infection with Pneumocystis carinii. They are frequently put on a regular drug regimen of Trimethoprim sulfa and/or inhaled pentamidine to avoid Pneumocystis pneumonia.

Resources

BOOKS

Johanson, Waldemar G. "Bacterial Meningitis." In Cecil Textbook of Medicine. Edited by J. Claude Bennett and Fred Plum. Philadelphia: W.B. Saunders, 1996.

Murray, Michael T., and Joseph E. Pizzorno. "Bronchitis and Pneumonia." In Encyclopedia of Natural Medicine. 2d ed. Rocklin, CA: Prima Publishing, 1998.

"Pneumonia." Section 6, Chapter 73 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 1999.

Ray, C. George. "Lower Respiratory Tract Infections." In Sherris Medical Microbiology: An Introduction to Infectious Diseases. Edited by Kenneth J. Ryan. Norwalk, CT: Appleton and Lange, 1994.

PERIODICALS

Arias, E., and B. L. Smith. "Deaths: Preliminary Data for 2001." National Vital Statistics Reports 51 (March 14, 2003): 1–44.

Birnbaum, Howard G., Melissa Morley, Paul E. Greenberg, et al. "Economic Burden of Pneumonia in an Employed Population." Archives of Internal Medicine 161 (December 10, 2001): 2725-2732.

Curran, M., D. Simpson, and C. Perry. "Ertapenem: A Review of Its Use in the Management of Bacterial Infections." Drugs 63 (2003): 1855–1878.

Lyseng-Williamson, K. A., and K. L. Goa. "Linezolid: In Infants and Children with Severe Gram-Positive Infections." Paediatric Drugs 5 (2003): 419–429.

"New Research Shows That Pneumonia, Septic Shock Run in Families." Genomics & Genetics Weekly (November 16, 2001): 13.

"Outbreak of Severe Acute Respiratory Syndrome—Worldwide, 2003." Morbidity and Mortality Weekly Report 52 (March 21, 2003): 226–228.

"Update: Outbreak of Severe Acute Respiratory Syndrome—Worldwide, 2003." Morbidity and Mortality Weekly Report 52 (March 28, 2003): 241–246, 248.

Worcester, Sharon. "Ventilator-Linked Pneumonia." Internal Medicine News 34 (October 15, 2001): 32.

Wunderink, R. G., S. K. Cammarata, T. H. Oliphant, et al. " Continuation of a Randomized, Double-Blind, Multicenter Study of Linezolid Versus Vancomycin in the Treatment of Patients with Nosocomial Pneumonia." Clinical Therapeutics 25 (March 2003): 980–992.

ORGANIZATIONS

American Lung Association. <http://lungusa.org/noframes/index.html>.

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. <http://www.cdc.gov>.

Mai Tran

Rebecca J. Frey, PhD

Pneumonia

Introduction

Disease History, Characteristics, and Transmission

Scope and Distribution

Treatment and Prevention

Impacts and Issues

Primary Source Connection

BIBLIOGRAPHY

Introduction

Pneumonia is an inflammatory response of the lungs to the entry of an infective organism or other foreign material. It is an important disease, as it is the sixth leading cause of death in the United States, and the major cause of death from infection.

Pneumonia is a complex disease with many different causes and risk factors. It can affect people of any age, anywhere, although the very young and the very old are most vulnerable to an attack. Pneumonia is classified in two ways—according to its cause and according to its setting.

The cause of pneumonia can be viral, bacterial, mycobacterial, fungal, or even non-infective irritants.

The setting may be either within the community or in the hospital. These distinctions are important because they influence the choice of treatment. Before the advent of antibiotics, pneumonia was a greatly feared disease because it could kill so easily. Today, with effective treatment, most people can expect to make a full recovery from pneumonia.

Disease History, Characteristics, and Transmission

Pneumonia is unlike many other infectious diseases in that it cannot be attributed to infection by one, or just a few, specific microbes. The respiratory tract, consisting of the nose, pharynx (back of the throat), trachea (windpipe), and lungs, has various mechanisms to protect itself from microbes as well as foreign bodies, such as particulate pollution, food, liquid, or gas. The nose and trachea are lined with mucous membranes, which bear tiny beating hairs called cilia. The thick mucous traps any microbes or foreign particles as they enter through the nose and mouth and the cilia propel them back to the nose and mouth where they are expelled, by nose blowing, or are swallowed. This mechanism protects the bronchi, which are the tiny tubes fanning out to connect the trachea with the alveoli, the tiny air sacs making up the lung tissue.

The cough reflex is another of the lungs’ defenses against infection, expelling foreign material before it enters the lungs. Added to this is the immune system, which will trigger cells or antibodies to destroy any threatening microbes or other material. Therefore, microorganisms may colonize the upper part of the respiratory tract, without causing disease, or they may cause an infection such as a cold or influenza. With the usual defenses in place, they do not invade the lungs.

If these defenses break down for any reason—for instance, because of the use of a mechanical ventilator in the intensive care unit, or because of weakened immunity—infection may spread down to the lungs. The alveoli mediate gas exchange between the lungs and the blood—oxygen in, carbon dioxide out. They deal with anything that threatens this function, such as invading microbes or particulate matter, with a strong inflammatory response, which is the underlying mechanism of pneumonia. One of the main features of this inflammation is the production of a thick secretion or exudate by the lung tissue.

Over 100 different organisms can cause pneumonia, and the most significant of these depends on patient characteristics and the setting—whether in the community or in the hospital. Some of the most important viral causes of pneumonia include adenovirus, respiratory syncytial virus, influenza virus, parainfluenza virus, and cytomegalovirus. Among the bacteria that can cause pneumonia are Streptococcus pneumoniae, Chlamydia pneumoniae, Haemophilus influenzae, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Mycoplasma, which are organisms that have some of the characteristics of both bacteria and viruses, can also cause pneumonia.

Among AIDS patients, Pneumocystis carinii is a major cause of pneumonia as an opportunistic infection. Before the advent of AIDS, P. carinii pneumonia was rare and its sudden appearance alerted researchers to the emergence of a new disease. P. carinii is a fungus-like organism. Other fungi that cause pneumonia include Histoplasma capsulatum and Cryptococcus neoformans.

Pneumonia may follow an attack of influenza or even a cold, but it can also arise on its own. Anyone who suddenly starts to feel worse after flu or a cold needs to get medical advice immediately. The symptoms of pneumonia vary from mild to very severe, and they may be either gradual or sudden in onset. The nature of the symptoms also varies depending upon the infecting microbe and patient characteristics. A cough, which may be either dry or productive of green or rust-colored phlegm (a discharge from the lungs), is probably the most common symptom of pneumonia. Sometimes the patient will even cough up blood. Fever, chills, and breathlessness may also occur and there may be chest pain. However, older people may have few symptoms other than mental confusion.

Bacterial pneumonia tends to come on suddenly with fever, shaking chills, sweating, and chest pain. The cough usually produces thick greenish or yellow phlegm. The symptoms are usually more dramatic among those previously in good health.

In viral pneumonia, which is more common in the winter months, there is a dry cough, headache, fever, muscle pain, and fatigue. Breathlessness tends to develop as the disease goes on and the cough starts to produce white phlegm. Viral pneumonia is a particular threat to those with pre-existing heart or lung disease. If it does not clear up, a secondary bacterial pneumonia may take hold.

Mycoplasma pneumonia is sometimes called “walking pneumonia” because the symptoms are gradual and mild—indeed, patients are not always aware that they are ill. This form of pneumonia often strikes schoolchildren and young adults. It may account for up to one-third of all childhood cases.

The examining doctor will look for signs of pneumonia, such as an increase in respiration and pulse rate. Pneumonia also is associated with characteristic chest sounds—bubbling, cracking sounds called rales, and rumblings called ronchi—that indicate the presence of fluid within the alveoli. These can be heard when the doctor puts a stethoscope to the chest. Chest x-ray, and possibly computed tomography (CAT) scanning, are an important part of the diagnosis of pneumonia, since they will reveal characteristic opacities or shadows on the affected lung. (Pneumonia may affect one or both lungs.)

The complications of pneumonia include blood poisoning, pleural effusion, and lung abscess. The alveoli are in close contact with the bloodstream and so the infection may enter the bloodstream, causing what is commonly known as blood poisoning or septicemia. When bacteria enter the bloodstream, they can reach the other organs of the body in a short time, possibly resulting in multi-organ failure and death. In pleural effusion, fluid leaks from the lungs into the space between the pleura, which are the membranes covering the lungs and the inner surface of the chest wall. This fluid could become infected—a condition known as empyema—and may have to be drained or removed surgically. Finally, an abscess, which is a cavity containing pus-infected material, may form within the lungs as a result of pneumonia. Although treatable with antibiotics, a lung abscess occasionally must be removed surgically.

WORDS TO KNOW

ANTIBIOTIC RESISTANCE: The ability of bacteria to resist the actions of antibiotic drugs.

ASPIRATION: Aspiration is the drawing out of fluid from a part of the body; it can cause pneumonia when stomach contents are transferred to the lungs through vomiting

CILIA: Cilia, which are specialized arrangements of microtubules, have two general functions. They propel certain unicellular organisms, such as paramecium, through the water. In multicellular organisms, if cilia extend from stationary cells that are part of a tissue layer, they move fluid over the surface of the tissue.

NOSOCOMIAL: A nosocomial infection is an infection that is acquired in a hospital. More precisely, the Centers for Disease Control and Prevention in Atlanta, Georgia, defines a nosocomial infection as a localized infection or one that is widely spread throughout the body that results from an adverse reaction to an infectious microorganism or toxin that was not present at the time of admission to the hospital.

OPPORTUNISTIC INFECTION: An opportunistic infection is so named because it occurs in people whose immune systems are diminished or are not functioning normally; such infections are opportunistic insofar as the infectious agents take advantage of their hosts’ compromised immune systems and invade to cause disease.

The complications of pneumonia are more common among the elderly, the frail, and those with weakened immunity, such as HIV/AIDS patients. The prognosis of pneumonia depends upon the setting and the patient. In those over 65, mortality ranges from 5% to 65%. The overall death rate for community-acquired pneumonia (CAP) is less than 1%. This rises to around 14% for nosocomial or hospital-acquired pneumonia (HAP) and to around 40% for patients in the intensive care unit.

Pneumonia is not transmitted from one person to another. Instead, it involves aspiration of microbes into the lungs from a previously colonized airway, implying that the normal defense mechanisms of the respiratory tract have broken down for some reason. It can also develop through aspiration of stomach contents, gas, or particulate pollution, all of which may inflame lung tissue.

Scope and Distribution

The public health burden of pneumonia in the United States is considerable. There are three million cases of pneumonia each year, accounting for ten million physician visits, 600,000 hospital admissions, and more than 60,000 deaths. It is the sixth most common cause of death and the leading cause of death from infection. Pneumonia accounts for half of all deaths from infection in the United States. Worldwide, pneumonia is the leading cause of death among infants less than one year old.

Pneumonia can strike at any age, but infants and children under four years of age and those over 65 years old are most at risk. The elderly account for almost 90% of all deaths from pneumonia and influenza. In adults, strong risk factors for pneumonia include existing illnesses such as congestive heart failure, kidney disease, diabetes, chronic obstructive pulmonary disease, removal of the spleen, malnutrition, alcoholism, institutionalization, and dementia. Children and young adults with cystic fibrosis are especially at risk of pneumonia. For infants, low birth weight and low maternal age have been found to be risk factors for pneumonia.

Community-acquired pneumonia (CAP) refers to pneumonia contracted outside a hospital setting—that is, either at home in the community or in a nursing home, day care setting, school, or other place where people congregate. The cause of CAP is often viral, but bacteria are also important causes of CAP. Different species of bacteria are involved in causing CAP in different age groups. Streptococcus and pneumococcus are the most common causes of pneumonia, accounting for up to 35% of all cases. Streptococcus and Staphylococcus species of bacteria are found to be especially important in cases of pneumonia in newborns, while S. pneumoniae and H. influenzae infections are common in older children. S. pneumoniae infection is also found often in elderly people with pneumonia.

Hospital-acquired pneumonia (HAP) is one of the most significant nosocomial infections. It refers to pneumonia that develops 48 hours after hospital admission. HAP occurs at a rate of 5–10 per 1,000 hospital admissions in the United States. Most cases occur in the intensive care unit or in post-surgical recovery. The risk of HAP is 6–20 times greater among those on mechanical ventilation. This is because ventilation involves inserting a tube into the trachea, which disrupts the natural defenses of the respiratory tract. The microbiology of HAP has been found to differ from that of CAP with Klebsiella pneumoniae, Pseudomonas aeruginosa, Serratia, and Enterobacter species, all of which are gram-negative bacilli, being most often involved. The term gram-negative (or positive) refers to the way a bacterial species reacts with a common stain used in microscopic studies.

IN CONTEXT: DISEASE IN DEVELOPING NATIONS

Pneumonia is an infection of the lung that can be caused by nearly any class of organism known to cause human infections, including bacteria, viruses, fungi, and parasites. In the United States, pneumonia is one of the most common diseases leading to death, and the most common fatal infection acquired by already hospitalized patients. In developing countries, pneumonia and diarrhea are the most common causes of death.

Treatment and Prevention

Some cases of pneumonia need to be treated in the hospital and prompt assessment by a physician is needed, because the condition can progress rapidly. An increased respiratory rate, decreased blood pressure, increased temperature, and confusion are all potential indicators for hospital admission. Microbiological tests are often needed to confirm the infective organism.

However, the physician often needs to start empiric antibiotic treatment before the microbiology results are available. There is no effective treatment for viral pneumonia, which usually clears up on its own. In particular, antibiotics will not work against viruses. For those recovering from pneumonia at home, bed rest is important, along with plenty of fluids to help loosen mucus in the lungs. These patients should also be sure to stay away from those with weakened immunity, which may mean not visiting anyone in the hospital.

Many different antibiotics can be used to treat pneumonia. The American Thoracic Society has established guidelines to help physicians make a good choice of antibiotic for pneumonia, based upon the patient and the setting. For out-patients, amoxicillin, azithromycin, and levofloxacin are often used. The latter is one of a relatively new group of drugs called the respiratory fluoroquinolones, which are valuable because they can treat drug-resistant bacteria. In-patients not in intensive care may be given cefotaxime, while intensive care patients may be treated with a combination of drugs, such as cefotaxime with a fluoroquinolone. Sometimes treatment is given by injection, to get to the infection as quickly as possible. Patients with cystic fibrosis often need high doses of antibiotics and in combination.

Immunization against H. influenzae and pneumococcus is valuable in the prevention of CAP in the over65s and in those otherwise at risk, such as patients with cystic fibrosis. The latter protects against 23 different types of pneumococcus. HAP is preventable by good hospital hygiene, especially relating to mechanical ventilation. Elevation of the bed has been found useful in protecting the lower respiratory tract from infection. Prevention of pneumonia is important, because the complications of the condition can be so serious. And with the growth of drug-resistant strains of bacteria that can cause pneumonia, effective treatment can no longer be relied upon.

Impacts and Issues

William Oster, the great nineteenth century Canadian physician, called pneumonia “the old man's friend” because it often releases an elderly, frail, terminal patient from a catalog of severe medical complaints. However, not all patients with pneumonia fall in this category. HAP is the second most common nosocomial infection in the United States and the most serious in terms of morbidity and mortality, with 300,000 new cases a year, accounting for 1.2 billion U.S. dollars in healthcare costs.

The causes of HAP need addressing when they are preventable, such as violations in infection control, including insufficient handwashing, and the use of equipment that could be contaminated. However, the risk of HAP is inextricably linked to the nature of modern medicine, especially when it comes to intensive care. Mechanical ventilation may save the lives of the desperately ill, but it is also the leading cause of HAP because of the way in which it breaches the natural defenses of the respiratory tract against infection. Other invasive devices that are linked with a high risk of HAP include nasogastric intubation (a tube leading from the nasal passages to the stomach) for feeding an unconscious patient, and chest, abdominal, and head and neck surgery. Again, these can be life saving treatments, and health care workers and researchers are attempting to develop technologies and practices within the intensive care and surgical setting that can minimize the risk of pneumonia.

Another major concern arising from HAP is that the cause is often a multi-drug resistant organism. This means that the patient's upper respiratory tract has been colonized with such a resistant organism and it may be difficult to find an antibiotic within the armory available to the physician that can treat the pneumonia successfully. Antibiotic resistance is also a concern in CAP, as penicillin-resistant S. pneumoniae is increasingly common. The fight against antibiotic resistance is two-fold. Researchers must develop new classes of antibiotic, which act by mechanisms not previously known. And both existing and new antibiotics must be used sparingly. Overuse or misuse of antibiotics promotes the emergence of resistant strains. On exposure, the weaker strains die, leaving the more resistant ones to flourish. This is especially likely to happen when a patient does not finish a prescribed course because symptoms of the infection clear up. This is as true of pneumonia as of any other infection. Patients must be responsible and take their medication exactly as prescribed. Only then are the chances of killing resistant bacteria maximized.

Primary Source Connection

In the following journal article, author Carol Potera discusses a type of aspiration (inhalation) pneumonia seen after the 2004 Asian tsunami that was termed “tsunami lung.” Potera is a contributor to Environmental Health Perspectives, a journal devoted to the interaction between environmental factors and human and animal health.

In Disaster's Wake: Tsunami Lung

When the Asian tsunami struck on 26 December 2004, health authorities braced for an onslaught of waterborne illnesses including malaria and cholera, which often follow such disasters. But saltwater flooded the freshwater breeding grounds of the mosquitoes that spread malaria, and relief agencies quickly distributed bottled water, thwarting a cholera epidemic. Instead, a type of aspiration pneumonia named “tsunami lung” emerged and afflicted some survivors.

Tsunami lung occurs when people being swept by tsunami waves inhale saltwater contaminated with mud and bacteria. The resulting pneumonia-like infections normally are treated with antibiotics. However, the 2004 tsunami “wiped out the medical infrastructure, and anti-biotics were not available to treat infections in the early stages,” says David Systrom, a pulmonologist at Massachusetts General Hospital in Boston. Consequently, victims’ lung infections festered, entered the bloodstream, and spread to the brain, producing abscesses and neurological problems such as paralysis.

Systrom and colleagues volunteered to work on a medical disaster team with Project HOPE (Health Opportunities for People Everywhere) aboard the hospital ship U.S. Naval Ship Mercy off the coast of Banda Aceh, Sumatra. When they arrived three weeks after the tsunami hit, “we saw infections not seen in the United States since before the development of antibiotics,” says Systrom. Among them were about 25 cases of tsunami lung. “No one expected the number of tsunami lung cases we saw,” says Systrom. “It was not on the radar screen.”

The diagnosis of tsunami lung requires a chest radiograph and computed tomography scan of the brain to confirm abscesses. This sophisticated equipment was available on the hospital ship. “Only the most severe cases with central nervous system involvement made it to the ship,” says Systrom. The team suspects that hundreds of milder cases went unreported.

In the 23 June 2005 issue of the New England Journal of Medicine, the team describes the case of a 17-year-old girl who aspirated water and mud while engulfed by a wave and carried about half a mile. She developed pneumonia two weeks later and was treated at a local clinic with unknown medicines. A week later, the right side of her face drooped, her right arm and leg became paralyzed, and she stopped talking.

A chest radiograph revealed air and pus outside the lining of the lung (a condition known as hydropneumothorax), and a brain scan showed four abscesses. After the doctors treated her with a combination of intravenous antibiotics (imipenem until the stock of that drug ran out, then vancomycin, ceftazadime, and metronidazole), her speech and facial movement recovered first. When she moved her right leg and arm for the first time, she “burst into peals of laughter,” according to the report. She was transferred to an International Committee of the Red Cross-Crescent field hospital. “I suspect she'll fully recover,” says Sydney Cash, a neurologist at Massachusetts General Hospital and member of the team, who has since received pictures of her walking.

A combination of microbes likely contributes to tsunami lung, but no lab facility was available to culture and identify those found in the Indonesian patients before the Mercy arrived. However, in a letter published in the 4 April 2005 issue of the Medical Journal of Australia, Anthony Allworth, director of infectious diseases at Royal Brisbane and Women's Hospital, describes culturing Burkholderia pseudomallei from two tsunami lung patients in a land-based hospital and Nocardia species from a third.

B. pseudomallei lives in the Asian soil and water. Mark Pasternack, an infectious disease specialist at Massachusetts General Hospital who also served on the Mercy, says, “You do not have to directly aspirate Burkholderia to produce pneumonia…. After the tsunami, people had soft tissue injuries from being forced into objects, so they could have gotten Burkholderia from wounds or aspiration.”

Cash echoes this thought: “Natural disasters produce odd combinations of pathogens and unexpected ways for the body to be damaged that lead to unexpected clinical circumstances. [Medical disaster physicians need to] keep an open mind and expect the unexpected.”

Could an infection like tsunami lung emerge in victims of Hurricane Katrina? Probably not, speculates Pasternack. Although the water sweeping the Gulf Coast area may have been contaminated, “it was not forced down peoples’ lungs by high-speed waves,” he says. Therefore, aspiration pneumonia and its complications are unlikely to appear commonly during the Gulf Coast relief efforts.

Carol Potera

POTERA, CAROL. “IN DISASTER'S WAKE: TSUNAMI LUNG.” ENVIRONMENTAL HEALTH PERSPECTIVES 113 (2005): 11, 734.

See AlsoChlamydia pneumoniae; Haemophilus influenzae; MRSA; Nosocomial (Healthcare-Associated) Infections; Pneumocystis carinii Pneumonia.

BIBLIOGRAPHY

Books

Gates, Robert H. Infectious Disease Secrets. 2nd ed. Philadelphia: Hanley and Beltus, 2003.

Tan, James S. Expert Guide to Infectious Diseases. Philadelphia: American College of Physicians, 2001.

Wilson, Walter R., and Merle A. Sande. Current Diagnosis & Treatment in Infectious Diseases. New York: McGraw Hill, 2001.

Web Sites

American Lung Association. “Pneumonia Fact Sheet.”

April 2006. <http://www.lungusa.org/site/apps/nl/content3.asp?c=dvLUK9O0Eb=2060321content_id={08C669B0-E845-4C9C-8B1E-285348BC83BD}notoc=1> (accessed March 25, 2007).

Mayo Clinic. “Pneumonia.” May 12, 2005. <http://www.mayoclinic.com/health/pneumonia/DS00135> (accessed March 25, 2007).

Susan Aldridge

Pneumonia

Definition

Pneumonia is an infection of the lung that can be caused by nearly any class of organism known to cause human infections. These include bacteria, amoebae, viruses, fungi, and parasites. In the United States, pneumonia is the sixth most common disease leading to death ; 2 million Americans develop pneumonia each year, and 40,000-70,000 die from it. Pneumonia is also the most common fatal infection acquired by already hospitalized patients. In developing countries, pneumonia ties with diarrhea as the most common cause of death. Even in nonfatal cases, pneumonia is a significant economic burden on the health care system. One study estimates that people in the American workforce who develop pneumonia cost employers five times as much in health care as the average worker.

According to the Centers for Disease Control and Prevention (CDC), however, the number of deaths from pneumonia in the United States has declined slightly since 2001.

Description

Anatomy of the lung

To better understand pneumonia, it is important to understand the basic anatomic features of the respiratory system. The human respiratory system begins at the nose and mouth, where air is breathed in (inspired) and out (expired). The air tube extending from the nose is called the nasopharynx. The tube carrying air breathed in through the mouth is called the oropharynx. The nasopharynx and the oropharynx merge into the larynx. The oropharynx also carries swallowed substances, including food, water, and salivary secretion, which must pass into the esophagus and then the stomach. The larynx is protected by a trap door called the epiglottis. The epiglottis prevents substances that have been swallowed, as well as substances that have been regurgitated (thrown up), from heading down into the larynx and toward the lungs.

A useful method of picturing the respiratory system is to imagine an upside-down tree. The larynx flows into the trachea, which is the tree trunk, and thus the broadest part of the respiratory tree. The trachea divides into two tree limbs, the right and left bronchi. Each one of these branches off into multiple smaller bronchi, which course through the tissue of the lung. Each bronchus divides into tubes of smaller and smaller diameter, finally ending in the terminal bronchioles. The air sacs of the lung, in which oxygen-carbon dioxide exchange actually takes place, are clustered at the ends of the bronchioles like the leaves of a tree. They are called alveoli.

The tissue of the lung which serves only a supportive role for the bronchi, bronchioles, and alveoli is called the lung stroma.

Function of the respiratory system

The main function of the respiratory system is to provide oxygen, the most important energy source for the body's cells. Inspired air (the air you breath in) contains the oxygen, and travels down the respiratory tree to the alveoli. The oxygen moves out of the alveoli and is sent into circulation throughout the body as part of the red blood cells. The oxygen in the inspired air is exchanged within the alveoli for the waste product of human metabolism, carbon dioxide. The air you breathe out contains the gas called carbon dioxide. This gas leaves the alveoli during expiration. To restate this exchange of gases simply, you breathe in oxygen, you breathe out carbon dioxide

Respiratory system defenses

The healthy human lung is sterile. There are no normally resident bacteria or viruses (unlike the upper respiratory system and parts of the gastrointestinal system, where bacteria dwell even in a healthy state). There are multiple safeguards along the path of the respiratory system. These are designed to keep invading organisms from leading to infection.

The first line of defense includes the hair in the nostrils, which serves as a filter for large particles. The epiglottis is a trap door of sorts, designed to prevent food and other swallowed substances from entering the larynx and then trachea. Sneezing and coughing, both provoked by the presence of irritants within the respiratory system, help to clear such irritants from the respiratory tract.

Mucus, produced through the respiratory system, also serves to trap dust and infectious organisms. Tiny hair like projections (cilia) from cells lining the respiratory tract beat constantly. They move debris trapped by mucus upwards and out of the respiratory tract. This mechanism of protection is referred to as the mucociliary escalator.

Cells lining the respiratory tract produce several types of immune substances which protect against various organisms. Other cells (called macrophages) along the respiratory tract actually ingest and kill invading organisms.

The organisms that cause pneumonia, then, are usually carefully kept from entering the lungs by virtue of these host defenses. However, when an individual encounters a large number of organisms at once, the usual defenses may be overwhelmed, and infection may occur. This can happen either by inhaling contaminated air droplets, or by aspiration of organisms inhabiting the upper airways.

Conditions predisposing to pneumonia

In addition to exposure to sufficient quantities of causative organisms, certain conditions may make an individual more likely to become ill with pneumonia. Certainly, the lack of normal anatomical structure could result in an increased risk of pneumonia. For example, there are certain inherited defects of cilia which result in less effective protection. Cigarette smoke, inhaled directly by a smoker or second-hand by a innocent bystander, interferes significantly with ciliary function, as well as inhibiting macrophage function.

Stroke, seizures, alcohol, and various drugs interfere with the function of the epiglottis. This leads to a leaky seal on the trap door, with possible contamination by swallowed substances and/or regurgitated stomach contents. Alcohol and drugs also interfere with the normal cough reflex. This further decreases the chance of clearing unwanted debris from the respiratory tract.

Viruses may interfere with ciliary function, allowing themselves or other microorganism invaders (such as bacteria) access to the lower respiratory tract. One of the most important viruses is HIV (Human Immunodeficiency virus), the causative virus in AIDS (acquired immunodeficiency syndrome). In recent years this virus has resulted in a huge increase in the incidence of pneumonia. Because AIDS results in a general decreased effectiveness of many aspects of the host's immune system, a patient with AIDS is susceptible to all kinds of pneumonia. This includes some previously rare parasitic types which would be unable to cause illness in an individual possessing a normal immune system.

The elderly have a less effective mucociliary escalator, as well as changes in their immune system. This causes this age group to be more at risk for the development of pneumonia.

Various chronic conditions predispose a person to infection with pneumonia. These include asthma, cystic fibrosis, and neuromuscular diseases which may interfere with the seal of the epiglottis. Esophageal disorders may result in stomach contents passing upwards into the esophagus. This increases the risk of aspiration into the lungs of those stomach contents with their resident bacteria. Diabetes, sickle cell anemia, lymphoma, leukemia, and emphysema also predispose a person to pneumonia.

Genetic factors also appear to be involved in susceptibility to pneumonia. Certain changes in DNA appear to affect some patients' risk of developing such complications of pneumonia as septic shock.

Pneumonia is also one of the most frequent infectious complications of all types of surgery. Many drugs used during and after surgery may increase the risk of aspiration, impair the cough reflex, and cause a patient to underfill their lungs with air. Pain after surgery also discourages a patient from breathing deeply enough, and from coughing effectively.

Radiation treatment for breast cancer increases the risk of pneumonia in some patients by weakening lung tissue.

Causes and symptoms

The list of organisms which can cause pneumonia is very large, and includes nearly every class of infecting organism: viruses, bacteria, bacteria-like organisms, fungi, and parasites (including certain worms). Different organisms are more frequently encountered by different age groups. Further, other characteristics of an individual may place him or her at greater risk for infection by particular types of organisms:

• Viruses cause the majority of pneumonias in young children (especially respiratory syncytial virus, parainfluenza and influenza viruses, and adenovirus).
• Adults are more frequently infected with bacteria (such as Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus ).
• Pneumonia in older children and young adults is often caused by the bacteria-like Mycoplasma pneumoniae (the cause of what is often referred to as "walking" pneumonia).
• Pneumocystis carinii is an extremely important cause of pneumonia in patients with immune problems (such as patients being treated for cancer with chemotherapy, or patients with AIDS. Classically considered a parasite, it appears to be more related to fungi.
• People who have reason to come into contact with bird droppings, such as poultry workers, are at risk for pneumonia caused by the organism Chlamydia psittaci.
• A very large, serious outbreak of pneumonia occurred in 1976, when many people attending an American Legion convention were infected by a previously unknown organism. Subsequently named Legionella pneumophila, it causes what is now called "Legionnaire's disease." The organism was traced to air conditioning units in the convention's hotel.

Pneumonia is suspected in any patient who has fever, cough, chest pain, shortness of breath, and increased respirations (number of breaths per minute). Fever with a shaking chill is even more suspicious. Many patients cough up clumps of sputum, commonly known as spit. These secretions are produced in the alveoli during an infection or other inflammatory condition. They may appear streaked with pus or blood. Severe pneumonia results in the signs of oxygen deprivation. This includes blue appearance of the nail beds or lips (cyanosis ).

The invading organism causes symptoms, in part, by provoking an overly-strong immune response in the lungs. In other words, the immune system, which should help fight off infections, kicks into such high gear, that it damages the lung tissue and makes it more susceptible to infection. The small blood vessels in the lungs (capillaries) become leaky, and protein-rich fluid seeps into the alveoli. This results in less functional area for oxygen-carbon dioxide exchange. The patient becomes relatively oxygen deprived, while retaining potentially damaging carbon dioxide. The patient breathes faster and faster, in an effort to bring in more oxygen and blow off more carbon dioxide.

Mucus production is increased, and the leaky capillaries may tinge the mucus with blood. Mucus plugs actually further decrease the efficiency of gas exchange in the lung. The alveoli fill further with fluid and debris from the large number of white blood cells being produced to fight the infection.

Consolidation, a feature of bacterial pneumonias, occurrs when the alveoli, which are normally hollow air spaces within the lung, instead become solid, due to quantities of fluid and debris.

Viral pneumonias and mycoplasma pneumonias do not result in consolidation. These types of pneumonia primarily infect the walls of the alveoli and the stroma of the lung.

Severe acute respiratory syndrome (SARS)

Severe acute respiratory syndrome, or SARS, is a contagious and potentially fatal disease that first appeared in the form of a multi-country outbreak in early February 2003. Later that month, the CDC began to work with the World Health Organization (WHO) to investigate the cause(s) of SARS and to develop guidelines for infection control. SARS has been described as an "atypical pneumonia of unknown etiology;" by the end of March 2003, the disease agent was identified as a previously unknown coronavirus.

The early symptoms of SARS include a high fever with chills, headache, muscle cramps, and weakness. This early phase is followed by respiratory symptoms, usually a dry cough and painful or difficult breathing. Some patients require mechanical ventilation. The mortality rate of SARS is thought to be about 3%.

As of the end of March 2003, the CDC did not have clearly defined recommendations for treating SARS. Treatments that have been used include antibiotics known to be effective against bacterial pneumonia; ribavirin and other antiviral drugs ; and steroids.

Diagnosis

For the most part, diagnosis is based on the patient's report of symptoms, combined with examination of the chest. Listening with a stethoscope will reveal abnormal sounds, and tapping on the patient's back (which should yield a resonant sound due to air filling the alveoli) may instead yield a dull thump if the alveoli are filled with fluid and debris.

Laboratory diagnosis can be made of some bacterial pneumonias by staining sputum with special chemicals and looking at it under a microscope. Identification of the specific type of bacteria may require culturing the sputum (using the sputum sample to grow greater numbers of the bacteria in a lab dish.).

X-ray examination of the chest may reveal certain abnormal changes associated with pneumonia. Localized shadows obscuring areas of the lung may indicate a bacterial pneumonia, while streaky or patchy appearing changes in the x-ray picture may indicate viral or mycoplasma pneumonia. These changes on x ray, however, are known to lag in time behind the patient's actual symptoms.

Treatment

Prior to the discovery of penicillin antibiotics, bacterial pneumonia was almost always fatal. Today, antibiotics, especially given early in the course of the disease, are very effective against bacterial causes of pneumonia. Erythromycin and tetracycline improve recovery time for symptoms of mycoplasma pneumonia. They, do not, however, eradicate the organisms. Amantadine and acyclovir may be helpful against certain viral pneumonias.

A newer antibiotic named linezolid (Zyvox) is being used to treat penicillin-resistant organisms that cause pneumonia. Linezolid is the first of a new line of antibiotics known as oxazolidinones. Another new drug known as ertapenem (Invanz) is reported to be effective in treating bacterial pneumonia.

Prognosis

Prognosis varies according to the type of organism causing the infection. Recovery following pneumonia with Mycoplasma pneumoniae is nearly 100%. Staphylococcus pneumoniae has a death rate of 30-40%. Similarly, infections with a number of gram negative bacteria (such as those in the gastrointestinal tract which can cause infection following aspiration) have a death rate of 25-50%. Streptococcus pneumoniae, the most common organism causing pneumonia, produces a death rate of about 5%. More complications occur in the very young or very old individuals who have multiple areas of the lung infected simultaneously. Individuals with other chronic illnesses (including cirrhosis of the liver, congestive heart failure, individuals without a functioning spleen, and individuals who have other diseases that result in a weakened immune system, experience complications. Patients with immune disorders, various types of cancer, transplant patients, and AIDS patients also experience complications.

Prevention

Because many bacterial pneumonias occur in patients who are first infected with the influenza virus (the flu), yearly vaccination against influenza can decrease the risk of pneumonia for certain patients. This is particularly true of the elderly and people with chronic diseases (such as asthma, cystic fibrosis, other lung or heart diseases, sickle cell disease, diabetes, kidney disease, and forms of cancer).

A specific vaccine against Streptococcus pneumoniae is very protective, and should also be administered to patients with chronic illnesses.

Patients who have decreased immune resistance are at higher risk for infection with Pneumocystis carinii. They are frequently put on a regular drug regimen of trimethoprim sulfa and/or inhaled pentamidine to avoid pneumocystis pneumonia.

KEY TERMS

Alveoli— The little air sacs clustered at the ends of the bronchioles, in which oxygen-carbon dioxide exchange takes place.

Aspiration— A situation in which solids or liquids which should be swallowed into the stomach are instead breathed into the respiratory system.

Cilia— Hair-like projections from certain types of cells.

Consolidation— A condition in which lung tissue becomes firm and solid rather than elastic and air-filled because it has accumulated fluids and tissue debris.

Coronavirus— One of a family of RNA-containing viruses known to cause severe respiratory illnesses. In March 2003, a previously unknown coronavirus was identified as the causative agent of severe acute respiratory syndrome, or SARS.

Cyanosis— A bluish tinge to the skin that can occur when the blood oxygen level drops too low.

Sputum— Material produced within the alveoli in response to an infectious or inflammatory process.

Stroma— A term used to describe the supportive tissue surrounding a particular structure. An example is that tissue which surrounds and supports the actually functional lung tissue.

Resources

BOOKS

Beers, Mark H., MD, and Robert Berkow, MD., editors. "Pneumonia." In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

PERIODICALS

Arias, E., and B. L. Smith. "Deaths: Preliminary Data for 2001." National Vital Statistics Reports 51 (March 14, 2003): 1-44.

Birnbaum, Howard G., Melissa Morley, Paul E. Greenberg, et al. "Economic Burden of Pneumonia in an Employed Population." Archives of Internal Medicine 161 (December 10, 2001): 2725-2732.

Curran, M., D. Simpson, and C. Perry. "Ertapenem: A Review of Its Use in the Management of Bacterial Infections." Drugs 63 (2003): 1855-1878.

Lyseng-Williamson, K. A., and K. L. Goa. "Linezolid: In Infants and Children with Severe Gram-Positive Infections." Paediatric Drugs 5 (2003): 419-429.

"New Research Shows That Pneumonia, Septic Shock Run in Families." Genomics & Genetics Weekly November 16, 2001: 13.

"Outbreak of Severe Acute Respiratory Syndrome—Worldwide, 2003." Morbidity and Mortality Weekly Report 52 (March 21, 2003): 226-228.

"Update: Outbreak of Severe Acute Respiratory Syndrome—Worldwide, 2003." Morbidity and Mortality Weekly Report 52 (March 28, 2003): 241-246, 248.

Worcester, Sharon. "Ventilator-Linked Pneumonia." Internal Medicine News 34 (October 15, 2001): 32.

Wunderink, R. G., S. K. Cammarata, T. H. Oliphant, et al. "Continuation of a Randomized, Double-Blind, Multicenter Study of Linezolid Versus Vancomycin in the Treatment of Patients with Nosocomial Pneumonia." Clinical Therapeutics 25 (March 2003): 980-992.

ORGANIZATIONS

American Lung Association. 1740 Broadway, New York, NY 10019. (800) 586-4872. 〈http://www.lungusa.org〉.

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. 〈http://www.cdc.gov〉.

PNEUMONIA

Pneumonia is an infection involving the lungs. It may be caused by bacteria, viruses, or parasites. There are more than one hundred microbial causes of pneumonia. However, most cases of pneumonia are due to the following bacteria: Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, and Morayella (Branhamella ) catarrhalis. Clinically, pneumonia is characterized by a variety of symptoms and signs. Cough, which may be productive of purulent (yellow or green), mucopurulent (white with flecks of yellow or green), or "rusty" sputum (reddish-brown due to blood mixed in sputum), is common. Fever, chills, and pleuritic chest pain are other manifestations. Extrapulmonary symptoms such as nausea, vomiting, or diarrhea may occur. There is a spectrum of physical findings—the most common of which is crackles (sounds heard on listening with a stethoscope). Other findings that may be present include dullness to percussion, increased tactile and vocal fremitus, bronchial breathing, and a pleural friction rub. It is important to remember that pneumonia in the elderly may present with a paucity of respiratory symptoms and signs and instead may manifest as delirium. Delirium or acute confusion was found in nearly half of elderly patients with pneumonia studied by Riqueleme and colleagues compared with less than one-third of age- and sex-matched control subjects. Older patients with pneumonia complain of fewer symptoms than do younger patients with pneumonia.

Epidemiology

Pneumonia is a common and often serious illness. It is the sixth leading cause of death in the United States. About 600,000 persons are hospitalized with pneumonia each year and there are sixty-four million days of restricted activity due to this illness. One study shows that hospitalization for pneumonia is thirty times more likely among nursing home residents compared to adults living in the community.

Risk factors for pneumonia and predictors of outcome

Some of the risk factors for community-acquired pneumonia (CAP) in the elderly include alcoholism, asthma, and immunosuppression. For nursing home–acquired pneumonia, common risk factors include profound disability, old age, and male gender among others. Prognosis is especially poor for patients who are bedridden prior to the onset of pneumonia, those with a swallowing disorder or acute renal failure, or those with a respiratory rate greater than thirty breaths per minute. The mortality rates from pneumonia in elderly persons can be very high. The overall mortality rate for persons requiring admission to hospital for treatment of pneumonia ranges from 8 to 20 percent. The one-year mortality rate among nursing home patients following an episode of pneumonia is up to 40 percent. The major reason for these high mortality rates is due to the presence of various comorbid illnesses. For many elderly persons who have advanced Alzheimer's disease, strokes, and other illnesses, pneumonia is often the terminal event.

There is a high incidence of silent aspiration in elderly persons with community-acquired pneumonia. Kikuchi and colleagues examined the role of silent aspiration during sleep in elderly patients with CAP and found that 71 percent of the study patients aspirated compared with 10 percent of the control subjects. Just over 28 percent of patients with Alzheimer's disease and 51 percent of those with a stroke aspirated on videofluoroscopy. Croghan and others found that feeding tube placement in patients shown to aspirate on videofluoroscopy was associated with increased rate of pneumonia and death compared with those who aspirated but did not receive such a tube.

Diagnosis of the microbial etiology of the pneumonia

The signs and symptoms listed earlier suggest pneumonia to the physician. A chest radiograph is used to confirm the diagnosis (see accompanying images). The next step is to determine the microbial cause of the pneumonia. To do this a blood sample is collected for culture. Only 6 to 10 percent of these cultures will be positive. If a sputum sample can be coughed up it is submitted to the laboratory for culture. When examined under the microscope sputum contains many white blood cells and few squamous epithelial cells (these are cells that line the mouth). Examination of the sputum under the microscope can often suggest the infecting microorganism. For example, if only pairs of small round cells that stain with a common solution are seen in a sputum specimen with lots of white blood cells, then the most likely cause of the pneumonia is Streptococcus pneumoniae.

Culture of the sputum and identification of the microorganisms isolated usually requires two to three days. Isolation of a specific microorganism allows the physician to select an antibiotic that will be most effective against this microorganism. Unfortunately most elderly persons cannot produce a sputum specimen for culture. Under these circumstances the attending physician has to choose antibiotics based on the most likely cause of the pneumonia. Some patients who are critically ill as a result of the pneumonia may have a diagnostic bronchoscopy. Here a small tube is passed down the trachea to the bronchi and samples of respiratory secretions are aspirated for culture. Occasionally a lung biopsy is necessary for diagnosis. Other tests that can be used in the diagnosis of pneumonia include a urine sample to detect Legionella antigen.

Antibodies can be detected to a variety of microorganisms that cause pneumonia. Two samples of blood are obtained, one early on in the course of the illness and the other two to six weeks later. Such tests are currently used to diagnose infection with Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella species, and a variety of viral infections. A four-fold or more increase in the amount of antibody against a specific microorganism between the acute and convalescent phase serum samples indicate that that microorganism caused the pneumonia.

Treatment of community-acquired pneumonia

There are several components to the successful treatment of pneumonia. The first step is to decide the most appropriate site of care—home, hospital ward, hospital intensive care unit, and, for those who reside in a nursing home, either the nursing home or a hospital. The severity of the pneumonia and or the severity of the comorbid illnesses drive the decision as to the care site.

Patients with pneumonia generally prefer to be treated at home provided they can be assured they are not going to die. In many instances it is obvious that a patient is so sick that he or she should be treated in hospital. There is a pneumonia severity of illness scoring system that can be used to help in the decision as to the site of treatment (Fine et al.). The single best indication of severe pneumonia in an adult (who does not have pre-existing lung disease) is a respiratory rate (counted for one minute) of thirty-two breaths per minute or higher. The second step is deciding what is the most appropriate antibiotic. A number of effective antibiotics are available for the treatment of pneumonia (Naughton et al.; Bartlett et al.). Once the pneumonia is improving in elderly persons a functional and mental assessment should be carried out. The results of these studies guide the planning of discharge.

The final step is to arrange a follow-up chest X-ray and visit. Two percent of all persons presenting with pneumonia will have pneumonia as the first manifestation of cancer of the lung—the pneumonia is distal to an obstructed bronchus. If the pneumonia has not cleared on the sixth week follow-up chest X-ray, additional studies such as bronchoscopy may be required.

Prevention of pneumonia

Immunization with influenza vaccine once yearly and with pneumococcal vaccine every six years are important measures that can help prevent pneumonia. It is also important for those who smoke tobacco to stop smoking.

Thomas J. Marrie

See also Disease Presentation; Immune System; Influenza; Lung, Aging; Palliative Care; Tube Feeding; Urinary Tract Infection.

BIBLIOGRAPHY

Bartlett, J. G.; Breiman, R. F.; Mandell, L. A.; and File, T. M. "Community-Acquired Pneumonia in Adults: Guidelines for Management." Clinical Infectious Diseases 26 (1998): 811–838.

Crogan, J. E.; Burke, E. M.; Caplan, S; and Dennman, S. "Pilot Study of 12-Month Outcomes of Nursing Home Patients with Aspiration on Videofluroscopy." Dysphagia 9 (1994): 141–146.

Fine, M. J.; Auble, T. E.; Yearly, D. M.; et al. "A Prediction Rule to Identify Low-Risk Patients with Community-Acquired Pneumonia." New England Journal of Medicine 336 (1997): 243–250.

Kikuchi, R.; Watabe, N.; Konno, T.; Sekizawa, K; and Sasaki, H. "High Incidence of Silent Aspiration in Elderly Patients with Community-Acquired Pneumonia." American Journal of Respiratory and Critical Care Medicine 150 (1996): 251–253.

Loeb, M.; McGeer, A.; McArthur, M.; Walter, S.; and Simor, A. S. "Risk Factors for Pneumonia and Other Lower Respiratory Tract Infections in Elderly Residents of Long-Term Care Facilities." Archives of Internal Medicine 159 (1999): 2058–2064.

Marrie, T. J. "Epidemiology of Community-Acquired Pneumonia in the Elderly." Seminars in Respiratory Infection 5 (1990): 260–268.

Naughton, B. J., and Mylotte, J. M. "Treatment Guidelines for Nursing Home–Acquired Pneumonia Based on Community Practice." Journal of the American Geriatric Society 48 (2000): 82–88.

Riquelme, R.; Torres, A.; Wl-Ebiary, M.; Mensa, J.; Estruch, R.; Ruiz, M.; Angrill, J.; and Soler, N. "Community-Acquired Pneumonia in the Elderly." American Journal of Respiratory Critical Care Medicine. 156 (1997): 1908–1914.

Pneumonia

Definition

Pneumonia is an inflammation (irritation and swelling) of the lung usually caused by infection with bacteria, viruses , or other organisms. Pneumonia may also result from non-infectious causes, such as inhalation of food, liquids, gases, or dust. Pneumonia often develops as a complication of a pre-existing condition or infection or when a patient's immune system is weakened by a condition such as a simple viral respiratory tract infection or by influenza . Pneumonia and influenza together are ranked as the eighth leading cause of death in the United States, with pneumonia accounting for most of those deaths. In the elderly, pneumonia is the fourth leading cause of death and the leading infectious cause of death. In 2004, 60,207 people in the United States died of pneumonia.

Description

Pneumonia is one of the common and significant diseases of the elderly, especially those over the age of seventy. In general, the elderly are more susceptible to pneumonia than younger people. The elderly are also more likely to be hospitalized for pneumonia and need mechanical ventilation, resulting in a longer hospital stay than younger persons. In addition, many elderly people contract pneumonia while staying in a hospital for other conditions, because their immune systems are often compromised due to the condition that initially required treatment.

When a person has pneumonia, the air sacs in the lungs become filled with pus and other liquids, and oxygen transfer from the lungs to the blood stream is inhibited. Without sufficient oxygen, body cells may become to die. Lobar pneumonia affects a section (lobe) of a lung while bronchial pneumonia affects patches throughout both lungs.

Demographics

One sixth of the six million pneumonia cases that develop each year occur primarily in persons aged 65 years and older. Over 90 percent of all deaths from pneumonia occur in the older population. The incidence of development of pneumonia in the elderly is 20 to 40 illnesses per 1000 persons for pneumonia acquired in community settings, while the incidence rises to 100 to 250 per 1000 persons in cases acquired in long-term care facilities. An estimated 2.1 percent of elderly residents in long-term care facilities at any one time have pneumonia. About one billion dollars per year are spent on medical therapy to treat bacterial pneumonia in the elderly.

Causes and symptoms

The major risk factor for developing pneumonia in the elderly is the presence of other serious diseases. Characteristic symptoms of pneumonia include fever, cough, and sputum production.

Pneumonia is known to have more than thirty different causes. The five most common causes are:

• bacteria;
• viruses;
• Mycoplasmas;
• Other infectious agents such as fungi; and
• Various chemicals.

In more severe cases of pneumonia in the elderly, patients may be affected by more than one causative agent for pneumonia, such as several different bacterial strains.

Bacterial pneumonia often develops when the immune system of the body is weakened by factors such as tuberculosis , heart disease , diabetes, cancer , chronic liver disease, renal failure, old age, asthma ,

malnutrition , or alcoholism. The most common bacteria that causes pneumonia, Streptococcus pneumoniae is often present in the throats of healthy people, but works its way into the lungs to inflame the air sacs when immune resistance is lowered. As the infection develops, one or more lobes of the lungs becomes filled with liquids—the infection then can spread through the bloodstream throughout the body, causing diseases such as meningitis or bacteremia . The onset of pneumonia can be slow to sudden. In the worst cases, the patient experiences chills and shaking, chattering teeth, severe chest pain , and a cough producing rust- or greenish-colored mucus. The body temperature may rise to as high as 105 degrees Fahrenheit, with the patient sweating heavily and breathing rapidly. The pulse rate may increase and the lips and nail beds may turn blue, due to a lack of oxygen. There is a vaccine available to prevent pneumonia caused by S. pneumoniae.

Other bacteria that cause pneumonia, especially in institutional settings, include Klebsiella, Pseudomonas aeruginosa, Enterobacter species, Proteus species, Escherichia coli, and other gram negative bacteria. Strains of anaerobic bacteria can be aspirated into the lungs by the elderly due to conditions associated with aging (such as sedative use or neurological conditions) and cause pneumonia. Haemophilus influenzae is a bacteria that causes pneumonia more frequently in patients with chronic bronchitis .

A small number of pneumonia cases are due to Legionnaires' disease. Legionnaires' disease is caused by bacteria known as Legionella pneumophila, as well as other species of Legionella. The Legionella bacteria can live in water and have been spread through air conditioning systems in hotels and hospitals. This disease was found and given its name when there was an outbreak of respiratory illness that caused twenty nine deaths among American Legion members who were attending a convention in a Philadelphia hotel in 1976. The causative organism was a common contaminant of water systems that was responsible for earlier epidemics of pneumonia that had not been identified in earlier outbreaks. Susceptibility to Legionnaires' disease increases with increasing age.

Half of all pneumonia cases are caused by viruses, including the influenza virus, parainfluenza virus, adenovirus, rhinovirus, herpes simplex virus, respiratory synctial virus, hantavirus, and cytomegalovirus. Many of these pneumonia infections are mild and may last only a short time. However pneumonia caused by the influenza virus may be severe and occasionally fatal. The symptoms of influenza pneumonia are similar to those of influenza, including fever, dry cough, headache, muscle pain, and weakness. However, within 12 to 36 hours, breathlessness develops, and the coughing increases, with a small amount of mucus produced. Patients have a high fever and may develop blueness of the lips. Eighty percent of deaths in recent influenza epidemics occurred in persons aged 65 and older, mostly due to development of complications such as sepsis or acute respiratory distress syndrome. Viral pneumonia can be further complicated by development of bacterial pneumonia.

Pneumonia caused by Mycoplasma pneumoniae is a common cause of pneumonia that is usually not a significant threat to the health of the elderly, as it usually affects people younger than 40. Persons at highest risk for mycoplasma pneumonia are those living or working in crowded areas such as schools and homeless shelters, although many people who contract mycoplasma pneumonia have no identifiable risk factor. Symptoms typical of pneumonia are usually mild and appear over a period of one to three weeks. They may become more severe in some people.

Pneumocystis carinii pneumonia (PCP) is caused by a fungus, Pneumocystis jiroveci (formerly called Pneumocystis carinii). PCP develops in persons with weakened immune systems from causes such as cancer, chronic use of corticosteroids or other

QUESTIONS TO ASK YOUR DOCTOR

• What type of pneumonia do I have?
• What types of diagnostic tests do I need?
• What is the treatment required for my type of pneumonia?

medications that affect the immune system, HIV/AIDS, or solid organ and/or bone marrow transplants. Symptoms of PCP include Symptoms a mild and dry cough, fever, rapid breathing, and shortness of breath, especially upon exercise or activity activity. PCP was a rare disease before the AIDS disease developed.

Chemical pneumonia is an unusual type of lung irritation. Although pneumonia usually is caused by a bacteria or virus, in chemical pneumonia, inflammation of lung tissue can be caused by many types of chemicals, including liquids, gases, and small particles, such as dust or fumes. Only a small percentage of pneumonias are caused by chemicals. Some chemicals only harm the lungs; however, some toxic chemicals may affect other organs in addition to the lungs and can result in serious organ damage or death. Aspiration pneumonia is another form of chemical pneumonia, where oral secretions or stomach contents are aspirated into the lungs. Inflammation develops from the toxic effects of stomach acid and enzymes on lung tissue. Symptoms of chemical pneumonia may include:

• burning of the nose, eyes, lips, mouth, and throat;
• dry cough;
• wet cough producing clear, yellow, or green mucus;
• cough producing blood or frothy pink matter;
• nausea or abdominal pain;
• chest pain;
• shortness of breath;
• painful breathing or pleuritis (an inflammation of the outside covering of the lungs);
• headache;
• flu symptoms;
• weakness or a general ill feeling; and/or
• delirium or disorientation.

Diagnosis

Tests that are performed to diagnosis pneumonia and its causes include:

• sputum culture (a test to detect and identify bacteria or fungi that are infecting the lungs);
• blood tests for antibodies to specific viruses;
• chest x rays;
• bronchoscopy; and/or
• open lung biopsy (only in very severe cases).

However, the intensity of symptoms and clinical manifestations of pneumonia are often less in the elderly than in younger patients, thus complicating diagnosis of the disease. The elderly may lose lung capacity as they age, making it harder for them to cough productively. They are also often used to feeling ill so may not recognize new symptoms of illness. Elderly people with pneumonia commonly exhibit acute confusion or delirium and deterioration of base metabolic functions.

Treatment

Bacterial pneumonia illnesses are treated with antibiotics . Although antibiotics will not be effective for viral pneumonia, in some cases if the cause of the disease is not known, antibiotics may be prescribed as a precaution. The specific antibiotic used will be dependent on the specific organism causing the pneumonia. The resistance of bacteria to commonly used antibiotics may complicate the treatment of pneumonia in the elderly.

Antiviral drugs may be useful for severe cases of viral pneumonia, although generally there is no cure for viral pneumonia. For persons with chronic diseases, severe symptoms, or low oxygen levels, hospitalization may be required to provide intravenous administration of antibiotics and oxygen therapy and to prevent dehydration .

For patients with pneumonia who develop dyspnea (difficult or painful breathing), opiod painkillers may be used to relieve painful symptoms. The use of sedatives should be avoided so as not to inhibit the ability of the patient to breathe deeply and cough. The use of corticosteroids to reduce wheezing has been shown to decrease mortality in persons with underlying lung diseases.

The treatment regimen must be continued according to the physician's recommendation to prevent reoccurrence of the disease. Relapses can be more severe than the original infection.

Nutrition/Dietetic concerns

In general, elderly persons who make good food choices may be better prepared to withstand the adverse effects of pneumonia, as there is some indication that malnutrition is a risk factor for pneumonia in the elderly. Vitamin supplementation may help the

elderly avoid contracting pneumonia or recover more quickly. In addition, a study conducted by the United States Department of Agriculture Human Nutrition Research Center on Aging at Tufts University Nutritional Immunology Laboratory of the United States Department of Agriculture has shown that daily zinc intake may help nursing home residents who are susceptible to pneumonia, especially those with low serum zinc concentrations in their blood, reduce their risk of developing pneumonia.

KEY TERMS

Acute respiratory distress syndrome —A serious reaction to various forms of injuries to the lung, which is characterized by inflammation of the lung, leading to impaired gas exchange and release of inflammatory mediators causing inflammation and low blood oxygen and frequently resulting in multiple organ failure. This condition is life threatening and often lethal, usually requiring mechanical ventilation and admission to an intensive care unit.

Bacteremia —Presence of bacteria in the blood. The blood is normally a sterile environment, so the detection of bacteria in the blood is always abnormal. Bacteria can enter the bloodstream as a complication of infections (such as pneumonia or meningitis), during surgery, or due to catheters and other foreign bodies entering the arteries or veins (including intravenous drug abuse).

Bronchoscopy —The examination of the bronchi (the main airways of the lungs) using a flexible tube (bronchoscope). Bronchoscopy helps to evaluate and diagnose lung problems, assess blockages, obtain samples of tissue and/or fluid, and/or to help remove a foreign body

CD4 count —A measure of the strength of the immune system. HIV continually kills CD4 cells. Over time, the body can not replace these lost CD4 cells and their number declines. AS this happens, the body becomes more susceptible to infections. A normal CD4 count is 1000. The body starts to get more frequent common infections at around a count of 400. At around a CD4 count of 200, the body becomes susceptible to many unusual infections. It is best to start medications for HIV before the CD4 count drops below 200 to prevent these infections from developing.

Opiod —A chemical substance that has a morphine-like action in the body. The main use is for pain relief.

Meningitis —Inflammation of the protective membranes covering the central nervous system, known collectively as the meninges. Meningitis may develop in response to a number of causes, most prominently bacteria, viruses and other infectious agents, but also physical injury, cancer, or certain drugs. While some forms of meningitis are mild and resolve on their own, meningitis is a potentially serious condition due to the proximity of the inflammation to the brain and spinal cord.

Morbidity —The relative incidence of sickness and injury occurring among a given group of people.

Sepsis —Presence of various pus-forming and other pathogenic organisms, or their toxins, in the blood or tissues.

Therapy

Respiration therapy such as chest percussion, especially for frail, elderly patients who may have difficulty coughing, may also be necessary to remove secretions produced in the lungs.

Prognosis

The chances of an early recovery (within two to three weeks) from pneumonia are enhanced if the pneumonia is detected early, if the patient has a strong immune system, if the infection has not spread throughout the body, and if the patient is not suffering from other diseases. Early treatment with antibiotics can cure pneumonia illnesses caused by bacteria. Elderly or patients with debilitating diseases may not to respond well to treatment and may experience significant disability and reduced activity for months following pneumonia. Increasing age, chronic obstructive lung disease, and alcohol abuse increase the risks of prolonged illness. Elderly with pneumonia may even die from respiratory, liver, or heart failure.

Prevention

Measures that can be taken to prevent pneumonia include frequent washing of hands, elimination of the use of tobacco (which damages the ability of the lungs to withstand infections), and wearing of masks in dusty or moldy areas. Since pneumonia often follows common respiratory infections such as the cold or flu, an important preventive measure is to be alert to any symptoms of respiratory illness that last for more than a few days. The practice of deep breathing for patients recovering in the hospital from various diseases or surgeries is recommended to help prevent them from developing pneumonia.

A pneumonia vaccine is available to prevent pneumonia caused by S. pneumoniae. The vaccine is designed to develop protective antibodies against eighty to ninety percent of pneumonia illnesses caused by twenty-three types of S. pneumoniae, including most of the penicillin-resistant strains. Initially the recommendation was for a single lifetime vaccination, but it is now recommended that patients be re-vaccinated every six to ten years. Unfortunately the vaccine may be less effective in people who are most susceptible to contracting pneumonia and developing complications.

The pneumonia vaccine is covered by Medicare in the United States and by many private health plans. In 2005 sixty-six percent of persons aged 65 years and older received the pneumonia vaccine. However, only fifty-one percent of African Americans aged 65 years or older received the pneumonia vaccine, compared to sixty-eight percent of whites of the same age or older.

The flu vaccine helps prevent pneumonia caused by influenza viruses. This vaccine must be given yearly to protect against new viral strains.

Additional preventive therapymay be necessary for:

• AIDS patients with CD4 counts below 200
• People on chronic high-doses of corticosteroids
• People who have had previous episodes of PCP

Caregiver concerns

A critical role of a caregiver is to ensure compliance with and completion of the treatment regimen for the elderly patient. Care givers can also help patients with pneumonia who are recovering at home by encouraging them to drink fluids to loosen secretions and bring up phlegm and perform household chores so the patients can rest. The care giver should also be aware of potential drug interactions with other medications that the patient may be taking (for example, warfarin and antibiotics). Regular communication between the physician and the care giver is essential.

Resources

BOOKS

Fein, Alan, and Grossman, Ronald. Diagnosis and Management of Pneumonia ad Other Respiratory Infections. West Islip, NY: Professional Communications, Inc., 2006.

ICON Health Publications. Bacterial Pneumonia—A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References. San Diego, CA: ICON Health Publications, 2004.

Niederman, Michael S. (ed.) Severe Pneumonia (Lung Biology in Health and Disease). London, United Kingdom: Informa Healthcare, 2005.

Petty, Thomas (ed.) and Seebass, James S. (ed.) Pulmonary Disorders of the Elderly: Diagnosis, Prevention, and Treatment. Philadelphia, PA: American College of Physicians, 2007.

ORGANIZATIONS

American Lung Association, 61 Broadway, 6th Floor, New York, New York, 10006, 212-315-8700, 800-586-4872, http://www.lungusa.org.

Judith L. Sims