Effects of expiratory positive airway pressure vs continuous positive airway pressure in conscious, spontaneously breathing dogs.

Abstract

The purpose of this study was to compare the cardiopulmonary effects of expiratory positive airway pressure (EPAP) and continuous positive airway pressure (CPAP) in conscious, spontaneously breathing dogs. Nine conscious dogs with elec- tromagnetic flow probes on their pulmonary arteries, catheters in their left atria and pulmo- nary arteries, and chronic tracheostomies, stood partially supported by slings, and breathed 100% oxygen through endotracheal tubes, pneumotachographs, and nonrebreathing valves which were part of either an EPAP or CPAP system. The effects of EPAP only were studied on four dogs while five were exposed to both EPAP and CPAP. After a 20-min control period, they breathed through either the EPAP or CPAP system for 10 min each under 5-, lo-, 15, and 20-cm H,O airway pressure. The mean pulmonary artery pressure, mean left atrial pressure, pulmonary vascular resistance, and minute ventilation were found to be significantly higher in the CPAP-treated group. Stroke volume and cardiac output were significantly higher in the EPAP-treated group. Both groups showed a significant carbon dioxide retention. Positive end-expiratory pressure, in conjunction with mechanical ventilation, is often used in the treatment of patients with pulmonary edema and adult respiratory distress syndrome. One potential disad- vantage of this therapy is a decrease in car- diac output (1 - 3).