The influence of PEEP ventilation on organ blood flow and peripheral oxygen delivery.

In an experimental study including 10 dogs with intact lungs (group I) and 10 dogs with oleic acid-induced pulmonary edema (group II), the effects of PEEP 10 and 20 (cm H20) on central hemodynamics, lung function, organ blood flow and tissue PO2 (liver and skeletal muscle) were examined. In both groups, PEEP resulted in a significant fall of cardiac output (CO) despite volume substitution. In group I, flow was redistributed favouring brain, heart, kidneys, and adrenals, at the expense of stomach, pancreas and and thyroid gland. Animals with pulmonary edema and consequently lower absolute values of CO showed a more uniform reduction of organ perfusion sparing only brain and heart PEEP 10 led to a marginal improvement of tissue oxygenation, whereas PEEP 20 resulted in a deterioration of local PO2 associated with a decrease in O2 transport. It is concluded that whenever PEEP is applied, a reduction and redistribution of CO may occur possibly jeopardizing tissue oxygenation and thus interfering with organ function.