Sir.—A recent article by Kirkpatrick et al, which appeared in the October issue of the Journal (128:496, 1974), reports a high incidence of pulmonary air leaks in patients with respiratory distress syndrome who were treated with assisted ventilation by means of a volume-controlled ventilator. The figures included in the article consisted of reproductions of the chest roentgenograms of several patients. The endotracheal tubes in some of them seem to be at or beyond the carina. If an endotracheal tube inadvertently slips down into one bronchus, then the hazard exists of introducing the entire volume of air into one lung when using a volume-cycled ventilator and of producing atelectasis on the opposite side. This could potentially produce a pulmonary air leak that may be prevented by keeping the tip of the endotracheal tube at least 2 cm above the carina.