Effects of End-Inspiratory Pause on Respiratory Function in the Patients Undergone Open-Chest Surgery

Abstract

Effects of end-inspiratory pause (EIP) on respiratory function were studied in 10 patients operated curatively for esophageal cancer. During intrathoracic manipulation, markedly decreased Pa02, and increased A-aD02 and Qs/Qt were observed suggesting the occurrence of plenty of atelectatic alveoli, while no significant change in PaCO2 nor VD/VT was recognized. The impaired oxygenation was gradually improved with a stepwise increment of EIP added to the controlled ventilation with 5 cmH20 of positive end-expiratory pressure (PEEP) after chest was closed. With 5% of EIP, A-aD02 and Qs/Qt decreased significantly, but not any change in ventilation was obtained. When EIP was increased to 10%, Pa02 increased remarkably and A-aD02, Qs/Qt and VD/VT decreased without significant change in circulation. By 15% of EIP, no more improvement in Pa02 nor A-aD02 was obtained in spite of decrease in Qs/Qt and VD/VT. Arterial blood pressure decreased significantly followed by an increase in mean airway pressure. Considering that essential time for the redistribution of inspired gas between lung compartments is 0.4 sec and that excessive positive airway pressure is harmful to circulation, 10% of EIP with 5 cm H2O PEEP was concluded to be the most suitable combination in the controlled ventilation for the patients undergone open-chest surgery. © 1980, Tohoku University Medical Press. All rights reserved.