Apneic Oxygenation in Man

Abstract

When man becomes apneic after preliminary oxygenation, there is a marked difference in the rate of arterial deoxygenation depending on whether the airway is open to room air or attached to an oxygen reservoir. Polarographic arterial Po2 studies show a rapid rate of fall in Pao2 when atmospheric air (containing 80% N) moves down the airway. In the case of pure oxygen reaching the alveolar space, high Po2 values greater than 400 mm. of mercury were observed even after 5 minutes of apnea. On the other hand, air with its high nitrogen content dilutes alveolar oxygen. In general, oxygen uptake is inhibited as the alveolar oxygen tension falls. Other physiological factors operating during apnea and responsible for limiting adequate oxygen uptake are discussed. There are numerous clinical situations involving apnea in which it is desirable to know the rate of arterial deoxygenation. From these oxygen tension data it is evident that in the healthy patient during respiratory arrest, hypoxia can be avoided for specific periods of time by means of apneic oxygenation. However, caution should be observed in prolonging apnea in the poor risk patient who has a deficiency in pulmonary ventilation.