Detrimental effects of removing end-expiratory pressure prior to endotracheal extubation

Abstract

Patients recovering from acute respiratory insufficiency are usually not extubated until they can ventilate adequately while breathing spontaneously at ambient end-expiratory pressure (T-tube). It is hypothesized that this period of T-tube breathing might be detrimental to gas exchange since the endotracheal tube abolishes the expiratory retard produced by the glottis and thereby inhibits the patient's ability to maintain adequate functional residual capacity (FRC). To test this hypothesis, pulmonary function of 17 patients was compared during T-tube breathing and Continuous Positive Airway Pressure (CPAP) and after extubation. Intrapulmonary shunt was higher (p less than 0.05) and arterial PO2 and FRC were lower (p less than 0.05) during T-tube breathing than during CPAP or after extubation. In contrast, shunt, PaO2 and FRC were similar during CPAP and after extubation. Furthermore, after extubation there was an increase (p less than 0.05) in mean expiratory airway pressure as compared to T-tube breathing. A comparison of patients extubated from T-tube with patients extubated from CPAP showed no difference in postextubation shunt, PaO2 or FRC. These data suggest that endotracheal intubation should be accompanied by low levels of CPAP and that patients should be extubated directly from CPAP. The practice of placing patients in T-tube prior to extubation should be abandoned as unnecessary and potentially harmful.