Lung Ventilation, Artificial

a method of introducing air or oxygen into the respiratory tract when there is a disruption or intentional suspension of natural respiration (spontaneous ventilation of the lungs). Under normal conditions, entry of oxygen into the lungs occurs upon inspiration. Where there is disruption of natural lung ventilation (in certain diseases, drowning, and so forth and also to produce endotracheal narcosis, when respiration is intentionally suspended), artificial lung ventilation is applied, using intubation of the trachea, which permits connecting the respiratory tract with a reservoir from which gas (air, oxygen, narcotics) enters the lungs. If artificial lung ventilation is performed by hand—by rhythmic pressure on the gas reservoir (for example, of the sac of a narcotic apparatus)—the method is called hand artificial lung ventilation; if it is conducted by means of mechanical devices (a respirator or an apparatus for artificial lung ventilation), it is called mechanical. In hand artificial lung ventilation, it is possible to produce active inhalation and only passive exhalation. Various types of apparatus for artificial lung ventilation make it possible to produce positive pressure on inhalation and any magnitude (from 0 to 30 cm water column) of negative pressure on exhalation. In the USSR various apparatus have been created for artificial lung ventilation, including the RO-5, RD-200, and “Vita.” If the apparatus automatically maintains the necessary volume of artificial lung ventilation, ensuring constancy of blood gas content (principally the acid-alkaline balance), the artificial lung ventilation is called automatic. The apparatus ROA-1 has been produced in the USSR for automatic artificial lung ventilation. In order to facilitate artificial lung ventilation, muscle relaxants are used—that is, preparations that shut down natural respiration. When natural lung ventilation is maintained but is ineffective, auxiliary artificial lung ventilation is carried out, in which a volume of gas insufficient for adequate ventilation is “strengthened” at the time of inhalation. Artificial lung ventilation is performed according to three systems of gas circulation—semiopen, semiclosed (the most frequently used), and closed. In conducting artificial lung ventilation by the semiopen system, which ensures the most effective removal of carbon dioxide from the body without using a special absorbent, inhalation is accomplished from the reservoir of gas, whereas exhalation is accomplished passively into the surrounding atmosphere. The advantage of this system consists in the absence of resistance to exhalation; its drawbacks are the necessity of using a large flow of gas, the danger of lowering the carbon dioxide content of the blood (hypocapnia), the large expenditure of narcotics, and their accumulation in the operating room. To perform artificial lung ventilation by the semiclosed system, inhalation is accomplished from the reservoir of gas, whereas exhalation is accomplished either passively or actively. In this system a portion of the exhaled gas enters the atmosphere, and a portion of it goes back to the reservoir. An absorbent of carbon dioxide gas is placed in the path of the exhaled gas. The closed system ensures complete dissociation of the respiratory tract from the surrounding atmosphere. Since all the exhaled gas reenters the reservoir, use of a carbon dioxide absorbent is obligatory. The simplest methods of artificial lung ventilation are used in resuscitation. They consist of blowing the breath of the rescuer by mouth into the lungs of the patient through his mouth (“mouth-to-mouth”), or through his nose (“mouth-to-nose”), or of blowing in air from the surrounding atmosphere by means of special devices (bellows for artificial lung ventilation, “Ambu” bag). Artificial lung ventilation is effective only when patency of the respiratory tract is maintained.