The hemodynamic sequelae of conventional positive pressure ventilation (CPPV), airway pressure release ventilation (APRV), and spontaneous breathing were compared with continuous positive airway pressure (CPAP) in ten anesthetized dogs who had ventilatory failure with and without parenchymal lung injury. The APRV corrected respiratory acidosis without significantly effecting arterial blood oxygenation, venous admixture, cardiovascular function, or tissue oxygen utilization. Application of CPPV precipitated marked depressions in blood pressure, stroke volume, and cardiac output. A concomitant decrease in venous admixture did not compensate for these adverse cardiovascular effects. Deterioration of tissue oxygen delivery resulted in oxygen supply-demand imbalance during CPPV. The results of this experimental study indicate that if ventilatory augmentation of subjects who require CPAP is desired, APRV will enhance alveolar ventilation without compromising circulatory function and tissue oxygen balance, whereas CPPV will impair cardiovascular function significantly.