Respirator
Respirator
A respirator is a means to provide needed oxygen to a patient, to infuse medication directly into the lungs, or to provide the power to breathe to someone who is unable to do so on his own. A respirator may be needed following a serious trauma that interferes with the individual’s breathing or for a person who has contracted a disease such as poliomyelitis that has affected the nerves that control respiration. Also, a respirator often breathes for an individual who has had surgery because the muscle relaxants that are given for the procedure may render the respiratory muscles inactive.
Respirators come in many forms. A simple tube that discharges oxygen into the nose is the simplest. This device does not breathe for the patient, but enriches his air intake with oxygen.
other respirators are mechanical ventilators that force air into the patient’s lungs or expand his chest to allow air to move into the lungs. The primary indications that an individual needs artificial ventilation are inadequate breathing on the part of the patient; that is, apnea (no breathing) or hypoventilation (lowered rate of breathing), either of which results in lowered blood oxygen (hypoxemia) levels, the second indication. These patients will have inadequate lung expansion so too little air is moved in and out, respiratory muscle fatigue, unstable respiratory drive, or they work excessively at breathing. A patient with a closed head injury may need respiratory assistance to raise the pH of the blood to an alkaline level, which helps to prevent the brain from swelling.
Persons who have chronic obstructive pulmonary disease or emphysema, either of which will become worse over time, eventually will require mechanical ventilation. Because theirs is a chronic disease process that is incurable, however, physicians hold off the assisted ventilation as long as possible. Once on the assistance device the patient will need to use it for the rest of his life.
Thus, mechanical ventilation is applied to adjust alveolar ventilation to a level that is as normal as possible for each patient, to improve oxygenation, to reduce the work of breathing, and to provide prophylactic ventilation to patients who have had surgery.
Respirators may be either positive pressure or negative pressure types. Positive pressure ventilators force air into the lungs, negative pressure machines expand the chest to suck air into the lungs.
Positive pressure ventilators
Positive pressure ventilators are attached to a tube leading directly into the trachea or windpipe. These machines then force air into the lungs at sufficient force to expand the chest and lungs. The most sophisticated positive pressure respirators have an alarm system to sound if the device fails, gas blenders to infuse more than one gas into the lungs, pop-off valves to relieve pressure if the machine begins to build gas pressures to undesirable levels, humidifiers to moisturize the gas or nebulizers to infuse a medication into the gas stream, gas sampling ports, and thermometers.
Positive pressure respirators are pressure cycled or pressure limited, time cycled, volume cycled, or a combination of these.
Pressure cycled or pressure limited respirators force gas into the patient’s lungs until a preset pressure is reached. A valve in the machine closes off the gas stream and the patient exhales. These machines now are used only in cases of drug overdose or with comatose patients whose lungs are easy to ventilate. With this type of respirator the preset pressure is not always delivered. Changes in airway resistance can influence the pressure detected by the machine so the gas may be cut off at what the machine detects as the set pressure when in fact the gas entering the lungs is far below the desired level. The postoperative patient who may have improved lung mechanics because of muscle relaxants given for surgery may become overventilated because resistance to the infusion is lower and the preset pressure is not attained until more than the desired level of gas has been delivered. Bronchial spasms also may influence the amount of gas reaching the lungs. The spasmodic bronchi will reduce in diameter and increase the resistance to the pump, so the preset pressure is detected at too low a level.
Volume cycled machines deliver a preset volume of gas into the lungs without regard for pressure. These machines are capable of delivering gas at high pressure, so they can overcome respiratory system resistance such as stiff lungs to administer the needed oxygen. They are used often in critical care situations.
Time-cycled machines, as the name implies, deliver gas for a set time, shut off to allow the patient to exhale, then deliver again for the set time. Pressure and flow of the gas may vary over the time, depending upon patient characteristics, but these factors are not considered with time-cycled machines.
Any of these positive pressure machines now can be controlled by computer and the volume, time, or pressure reset from breath to breath, according to need.
A unique type of positive pressure apparatus is designed to deliver very rapid, shallow breaths over a short time. Some are designed to deliver 60-100 breaths per minute, others 100-400 breaths, and a very high frequency oscillator is available to deliver very small tidal volumes of gas at the rate of 900-3,000 breaths a minute. These small volumes provide oxygenation at lower positive pressures. This may be important in that it reduces cardiac depression and does not interfere with blood return to the heart. Also, the patient requires less sedation.
Negative pressure ventilators
Negative pressure ventilators do not pump air into the lungs. Instead they expand the chest to suck
KEY TERMS
Alveolar— Reference to the alveoli, the tiny air sacs of the lungs that exchange oxygen for carbon dioxide in the blood.
Bronchiolar— Reference to the bronchioles, the small air tubes that supply air to the alveoli in the lungs.
air into the lungs. These respirators come in three types: the tank, the cuirass, and body wrap.
The tank negative pressure respirator is commonly called the iron lung. Familiar during the poliomyelitis epidemic of the 1950s, the tank is a cylindrical container into which the patient is placed with his head protruding from an opening at one end. Air in the tank is sucked out periodically, which expands the patient’s chest to force him to inhale. Then the pressure in the tank is normalized and the patient exhales. Of course, the patient in an iron lung is immobile. One side effect of long-term iron lung occupancy is the possibility of so-called tank shock, the pooling of blood in the patient’s abdomen, which reduces venous return to the right atrium of the heart.
A more convenient form of negative pressure respirator is called the cuirass, or chest shell. It is a molded, plastic dome that fits closely to the patient’s body over the chest. As in the iron lung, the air is pumped out of the cuirass, which forces the chest to expand and air to be pulled into the lungs. When the pressure is normalized the chest relaxes and the patient exhales. The primary problem with the cuirass is that a poorly fitted one can cause pressure sores at the points where the seal is not adequate.
The pulmowrap is an impervious wrapping placed around the patient and connected to a pump. Here again air is removed from the wrap to expand the lungs.
See also Respiratory diseases.
Resources
BOOKS
Parker, Phillip M. The 2007-2012 Outlook for Incubators,Inhalators, Respirators, Resuscitators and other Breathing Devices. New York: ICON Group International, 2006.
Raihans, Gyan, Bhawani Pathak. Practical Guide to Respirator Usage in Industry. 2nd. ed. Elsevier, ON: 2006.
Larry Blaser
Respirator
Respirator
A respirator is a means to provide needed oxygen to a patient, to infuse medication directly into the lungs, or to provide the power to breathe to someone who is unable to do so on his own. A respirator may be needed following a serious trauma that interferes with the individual's breathing or for a person who has contracted a disease such as poliomyelitis that has affected the nerves that control respiration . Also, a respirator often breathes for an individual who has had surgery because the muscle relaxants that are given for the procedure may render the respiratory muscles inactive.
Respirators come in many forms. A simple tube that discharges oxygen into the nose is the simplest. This device does not breathe for the patient, but enriches his air intake with oxygen.
Other respirators are mechanical ventilators that force air into the patient's lungs or expand his chest to allow air to move into the lungs. The primary indications that an individual needs artificial ventilation are inadequate breathing on the part of the patient; that is, apnea (no breathing) or hypoventilation (lowered rate of breathing), either of which results in lowered blood oxygen (hypoxemia) levels, the second indication. These patients will have inadequate lung expansion so too little air is moved in and out, respiratory muscle fatigue, unstable respiratory drive, or they work excessively at breathing. A patient with a closed head injury may need respiratory assistance to raise the pH of the blood to an alkaline level, which helps to prevent the brain from swelling.
Persons who have chronic obstructive pulmonary disease or emphysema , either of which will become worse over time, eventually will require mechanical ventilation. Because theirs is a chronic disease process that is incurable, however, physicians hold off the assisted ventilation as long as possible. Once on the assistance device the patient will need to use it for the rest of his life.
Thus, mechanical ventilation is applied to adjust alveolar ventilation to a level that is as normal as possible for each patient, to improve oxygenation, to reduce the work of breathing, and to provide prophylactic ventilation to patients who have had surgery.
Respirators may be either positive pressure or negative pressure types. Positive pressure ventilators force air into the lungs, negative pressure machines expand the chest to suck air into the lungs.
Positive pressure ventilators
Positive pressure ventilators are attached to a tube leading directly into the trachea or windpipe. These machines then force air into the lungs at sufficient force to expand the chest and lungs. The most sophisticated positive pressure respirators have an alarm system to sound if the device fails, gas blenders to infuse more than one gas into the lungs, pop-off valves to relieve pressure if the machine begins to build gas pressures to undesirable levels, humidifiers to moisturize the gas or nebulizers to infuse a medication into the gas stream, gas sampling ports, and thermometers.
Positive pressure respirators are pressure cycled or pressure limited, time cycled, volume cycled, or a combination of these.
Pressure cycled or pressure limited respirators force gas into the patient's lungs until a preset pressure is reached. A valve in the machine closes off the gas stream and the patient exhales. These machines now are used only in cases of drug overdose or with comatose patients whose lungs are easy to ventilate. With this type of respirator the preset pressure is not always delivered. Changes in airway resistance can influence the pressure detected by the machine so the gas may be cut off at what the machine detects as the set pressure when in fact the gas entering the lungs is far below the desired level. The postoperative patient who may have improved lung mechanics because of muscle relaxants given for surgery may become overventilated because resistance to the infusion is lower and the preset pressure is not attained until more than the desired level of gas has been delivered. Bronchial spasms also may influence the amount of gas reaching the lungs. The spasmodic bronchi will reduce in diameter and increase the resistance to the pump, so the preset pressure is detected at too low a level.
Volume cycled machines deliver a preset volume of gas into the lungs without regard for pressure. These machines are capable of delivering gas at high pressure, so they can overcome respiratory system resistance such as stiff lungs to administer the needed oxygen. They are used often in critical care situations.
Time cycled machines, as the name implies, deliver gas for a set time, shut off to allow the patient to exhale, then deliver again for the set time. Pressure and flow of the gas may vary over the time, depending upon patient characteristics, but these factors are not considered with time cycled machines.
Any of these positive pressure machines now can be controlled by computer and the volume, time, or pressure reset from breath to breath, according to need.
A unique type of positive pressure apparatus is designed to deliver very rapid, shallow breaths over a short time. Some are designed to deliver 60-100 breaths per minute, others 100-400 breaths, and a very high frequency oscillator is available to deliver very small tidal volumes of gas at the rate of 900-3,000 breaths a minute. These small volumes provide oxygenation at lower positive pressures. This may be important in that it reduces cardiac depression and does not interfere with blood return to the heart . Also, the patient requires less sedation.
Negative pressure ventilators
Negative pressure ventilators do not pump air into the lungs. Instead they expand the chest to suck air into the lungs. These respirators come in three types: the tank, the cuirass, and body wrap.
The tank negative pressure respirator is commonly called the iron lung. Familiar during the poliomyelitis epidemic of the 1950s, the tank is a cylindrical container into which the patient is placed with his head protruding from an opening at one end. Air in the tank is sucked out periodically, which expands the patient's chest to force him to inhale. Then the pressure in the tank is normalized and the patient exhales. Of course, the patient in an iron lung is immobile. One side effect of long-term iron lung occupancy is the possibility of so-called tank shock, the pooling of blood in the patient's abdomen, which reduces venous return to the right atrium of the heart.
A more convenient form of negative pressure respirator is called the cuirass, or chest shell. It is a molded, plastic dome that fits closely to the patient's body over the chest. As in the iron lung, the air is pumped out of the cuirass, which forces the chest to expand and air to be pulled into the lungs. When the pressure is normalized the chest relaxes and the patient exhales. The primary problem with the cuirass is that a poorly fitted one can cause pressure sores at the points where the seal is not adequate.
The pulmowrap is an impervious wrapping placed around the patient and connected to a pump. Here again air is removed from the wrap to expand the lungs.
See also Respiratory diseases.
Resources
books
Larson, David E., ed. Mayo Clinic Family Health Book. New York: William Morrow, 1996.
Larry Blaser
KEY TERMS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .- Alveolar
—Reference to the alveoli, the tiny air sacs of the lungs that exchange oxygen for carbon dioxide in the blood.
- Bronchiolar
—Reference to the bronchioles, the small air tubes that supply air to the alveoli in the lungs.
respirator
res·pi·ra·tor / ˈrespəˌrātər/ • n. an apparatus worn over the mouth and nose or the entire face to prevent the inhalation of dust, smoke, or other noxious substances. ∎ an apparatus used to induce artificial respiration.
respirometer
respirator
1. a face mask for administering oxygen or other gas or for filtering harmful fumes, dust, etc.
2. see ventilator.