The complications that may occur as a result of endotracheal suctioning are generally avoidable or reversible. Tissue trauma can be prevented by the smooth introduction of the suction catheter along the proper course, by the use of regulated suction, and by the intermittent rather than continuous occlusion of the thumb port. Hypoxemia can be prevented by preoxygenation. The risk of cardiac arrhythmias can be minimized by preoxygenation and by the avoidance of repeated nasotracheal suctioning attempts. The practitioner can avoid precipitating subsegmental atelectasis by guarding against the application of active suction during endobronchial impaction of the catheter, and he can usually reverse any diffuse microatelectasis by hyperinflation after the suction-ing procedure. The repeated performance of nasotracheal suctioning predisposes a patient to pneumonia, as does insufficient attention to aseptic technique. Some degree of coughing by the patient being suctioned is often unavoidable, and the practitioner must be aware of possible complications of the cough itself. The bronchoconstriction that may occur secondary to the mechanical stimulus afforded by the catheter can be treated with bronchodilator drugs. Finally, the practitioner can facilitate entry of the catheter into the left mainstem bronchus by turning the patient's head to the right and/or by using angle-tipped catheters.