Abstract
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 electromagnetic flow probes on their pulmonary arteries, catheters in their left atria and pulmonary 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-, 10-, 15-, and 20-cm H2O 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.
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