Mechanisms responsible for the sustained fall in arterial oxygen tension after endotracheal suctioning in dogs.

Because a sustained fall in arterial oxygen tension (PaO2) was observed after endotracheal suctioning in previous studies on anesthetized dogs and in humans, this study was designed to investigate the nature of the fall, its duration, and its response to several challenges. Experiments were performed at weekly intervals using three anesthetized dogs. Each dog was subjected to five experiments. In spontaneously breathing dogs, the duration of the sustained fall after suctioning or after suction catheter insertion without application of suction pressure persisted through 15 minutes. At 30 minutes afterwards, PaO2 had partially or completely returned to control levels. One hyperinflation breath given after suctioning did not produce a lasting reversal of the sustained fall, and pretreatment with isoproterenol mist inhalations failed to prevent the sustained fall. In dogs which were mechanically ventilated both before and after suctioning or catheter insertion without application of suction pressure, three hyperinflations before suctioning or pretreatment with isoproterenol failed to prevent the sustained fall. The data supported the hypothesis that a reflex mechanism, initiated by mechanical stimulation of the airways, was responsible for the sustained fall in PaO2 observed.