The effect of change in cardiac output on intrapulmonary shunting

Abstract

Cardiac output was varied in 6 normal dogs and in 12 dogs with oleic acid induced pulmonary oedema by inducing hyper- and hypovolaemia produced by either transfusing or bleeding 15-20 ml of blood per kg body weight from the normovolaemic state. In normal dogs, a reduction in cardiac output of 42% was accompanied by a reduction in intrapulmonary shunt (Qs/Qt) from 9.8 to 6.4%. With induced pulmonary oedema, a 35% reduction in cardiac output was accompanied by a fall in Qs/Qt from 29 to 21.6%. In another series of experiments, mixed venous oxygen saturation was varied independently of cardiac output by means of veno-venous shunting of blood through a disc oxygenator. Decreasing SvO2 from 70 to 50% in normal lungs caused a decrease in QS/QT from 10.1 to 7.9% whilst in pulmonary oedema a decrease in Sv02 from 59.3 to 32.2% produced a decrease in Qs/Qt from 10.1 to 7.9% whilst in pulmonary oedema a decrease in SvO2 from 59.3 to 32.2% produced a decrease in Qs/Qt from 28.8 to 25.7%. © 1974 John Sherratt and Son Ltd.