Pulse oximetry during hemorrhagic hypotension and cardiopulmonary resuscitation in the rabbit

Abstract

A new transcutaneous oxygen saturation monitor, the pulse oximeter, was evaluated during hemorrhagic hypotension and cardipuimonary resuscitation (CPR) in six anesthetized and paralyzed adult rabbits. A combined transcutaneous oxygen and carbon dioxide electrode was evaluated simultaneously. The animals were initally subjected to graded hemorrhage and reinfusion. The transcutaneous saturation correlated significantly with arterial oxygen saturation until severe hypotension ensued and pulsation could no longer be detected. TcPO2 began to fall and TcPCO2 values began to rise, compared with arterial values, as the blood pressure fell below 100 mm Hg. Asystole was then induced and CPR instituted. Probe movement during CPR produced a fallacious appearance of pulsation and a spurious estimate of saturation. TcPO2 was between 0 to 4 torr and the TcPCO2 was in excess of 150 torr during CPR; neither correlated with arterial values. Pulse oximetry is a valuable method of continuously monitoring arterial oxygenation over a wide range of blood pressures, but it is adversely affected by probe movement. Further studies are required to determine the clinical limitations of this useful device.