Low minute ventilation alarm due to endotracheal tube hole

Abstract

Minute ventilation is the product of respiratory rate and tidal volume. Low values, despite adequate tidal volume and respiratory rate setting on the ventilator can be due to several causes. A rare cause can be a hole in the endotracheal tube (ETT) due to patient’s biting or chewing on it. We discuss a 34 year old lady, known patient of diabetes mellitus, rheumatic heart disease with severe mitral stenosis and chronic kidney disease. She had been referred to us from a nursing home after radical nephrectomy. Patient was on full mechanical ventilatory and inotropic support on the 5th postoperative day. A continuous ventilator alarm of low minute ventilation was noticed. The tidal volume delivered by ventilator was normal but the expired tidal volume was persistently low. Breathing circuit was checked for disconnection and integrity. ETT cuff pressure was checked and was found to be adequate (25 mmHg). She was given additional doses of the sedatives and muscle relaxants, which further decreased the minute ventilation. There was no bronchospasm on chest auscultation. We found a small rent in the ETT at the level of  molar teeth caused perhaps due to intermittent biting by the patient. In the mean time, patient’s SpO₂ dropped, so the hole was blocked with sterile, gloved hand and ventilation continued to attain 100% saturation. The ETT was then changed and thus ventilation normalized.