Effects of hyperbaric oxygen on ventricular performance, pulmonary blood volume, and systemic and pulmonary vascular resistance

The cardiovascular effects of hyperbaric (3 atm abs) air, 100% oxygen, and hyperbaric oxygen (HBO2) at 3 atm abs were investigated in 13 pentobarbital -anesthetized dogs. We measured heart rate, arterial pressure, pulmonary ar tery pressure, right atrial pressure, left and right ventricular pressure, and cardiac output. From these we determined end diastolic pressure, maxima l dp/dt, maximal (dp/p), end systolic elastance, cardiac work, and systemic (SVR) and pulmonary vascular resistance (PVR). Pulmonary blood volume was obtained from the mean transit time of ascorbic acid. The significant resul ts with HBO2 were a decrease in heart rate, cardiac output, and cardiac wor k. All left ventricular performance indices decreased, without a change in preload or afterload. In contrast, only right ventricular -dp/dt decreased. SVR increased but PVR did not change; 100% O-2 produced similar but less p ronounced responses. Hyperbaric air had only mild effects. Pulmonary blood volume and lung wet/dry ratio did not change. Our data suggest that HBO2 ma y act by a differential effect on the autonomic innervation of the right an d left ventricles. The resultant ventricular imbalance may be of clinical i mportance in the mechanism of pulmonary edema in patients in congestive hea rt failure undergoing hyperbaric therapy.