Tracheal tube cuff volume changes during extracorporeal circulation.

Changes in the volume of tracheal tube cuffs were examined during extracorporeal circulation to determine the influence of the composition of the inspired gases and of the gas within the cuff. The study was carried out on 90 patients who underwent coronary artery bypass grafting. When the cuff contains nitrous oxide at the start of extracorporeal circulation, the cuff volume decreases during bypass regardless of the composition of the inspired gases. When the cuff is filled with air or 100 per cent oxygen at the start of extracorporeal circulation and the inspired gas mixture consists of nitrous oxide and oxygen the cuff volume increases. When the cuff is deflated and then refilled with either room air or oxygen at the beginning of the extracorporeal circulation and the lungs are inflated with oxygen, the cuff volume change is minimal during bypass. This combination of gas prevents any undesirable change in the cuff volume. It appears desirable to monitor the tracheal tube cuff volume or pressure and to maintain a constant pressure and volume during bypass to prevent deflation and silent aspiration associated with cuff deflation, as well as to avoid mucosal damage due to excessive pressure in the cuff.