Cardiorespiratory effects of pneumatic trousers in critically ill patients.

Although pneumatic antishock trousers (PT) are widely used in prehospital and emergency care, little is known about their cardiorespiratory effects in critically ill patients. To examine this issue, we measured hemodynamic and oxygen metabolism variables in ten critically ill patients. All patients were studied with PTs uninflated, after five minutes of PT inflation to 40 mm Hg, and five minutes after PT deflation. Significant increase in mean arterial pressure, systemic vascular resistance, and pulmonary artery pressures were present after PT inflation. No significant changes in cardiac index, stroke index, arterial or mixed venous blood gas values, or oxygen delivery were found. There was a downward trend in VO2 that was on the border of statistical significance. Regression analysis of cardiorespiratory variables on blood volume demonstrated no physiologic effects of external counterpressure in hypovolemic, hypervolemic, or normovolemic patients. We concluded that PT inflation increases BP through its effects on peripheral resistance. No significant autotransfusion effect was present, and there was a suggestive impairment in oxygen metabolism.