Changes in shunt flow, compliance, and volume of lungs during apneic oxygenation

Abstract

Open-chested denitrogenated cats were studied during 30-min periods of apneic oxygenation. Two lung volumes were selected, one about 25% of total lung capacity (TLC), and the other one about 55% of TLC. Serial measurements were made during apnea of pulmonary shunt flow (Qs/Qt) and static pulmonary compliance (Cl). Lung volumes were measured at the beginning and end of the period of apnea. Apneic oxygenation at 25% TLC regularly was associated with increasing Qs/Qt, decreasing Cl, and loss of lung volume signifying atelectasis. None of these phenomena were observed at 55% TLC. These results are discussed as they relate to time-dependent changes in the surface characteristics of the alveolar lining.