The purpose of this study was to determine the frequency and severity of arterial oxygen desaturation during and after endotracheal suctioning in a group of ventilator-dependent patients and to evaluate the efficacy of several maneuvers designed to minimize desaturation. All patients were ventilated with volume-typed ventilator and a synchronized intermittent mandatory ventilation(SIMV) mode was utilized. In a given patint, each study consisted of four seperate passes of the suction catheter. The oxygen status of the patient was monitored with a digital pulse oxymeter. The mean baseline SaO2 for the group with each suctioning technique was very similar and did not differ significantly. When patints were suctioned off the ventilator without extra breaths, a significant drop occurred in the mean SaO2 And when the patients were suctioned with prebreaths and postbreaths off the ventilator or were maintained on the ventilator and suctioned through the swivel adaptor, there was a significant desaturation with all three methods. However, the mean desaturation of 0.8 percent with the swivel adaptor was significantly less(p<0.05) than the mean desaturation with any of the other three methods.