Pulmonary shunting during alveolar hypoventilation in the dog.

Pulmonary shunting (Qs/Qt) was measured in 16 anesthetized and paralyzed healthy beagle puppies during a control period when the end-expired CO2 concentration was 5 per cent and during alveolar hypoventilation, when the PaCO2 increased to 100 plus or minus 13 torr (mean plus or minus SE) and the ;Ha vecame 7.04 plus or minus 0.04. A constant tidal volume was maintained throughout each study, and hypoventilation was achieved by slowing only the respiratory rate. During the control period Qs/Qt was 2.9 plus or minus 0.3 per cent; during hypoventilation Qs/Qt was 3.2 plus or minus 0.3 per cent (an insignificant difference). The puppies, therefore, responded to anesthesia and alveolar hypoventilation without development of increased pulmonary shunts.