The Miller tracheal cuff pressure control valve. Clinical use in controlled and spontaneous ventilation

A constant pressure differential valve for the control of tracheal tube cuff pressure was tested under clinical conditions. Fifty-one patients underwent controlled ventilation and 20 patients were allowed to breathe spontaneously. Nitrous oxide 66% with oxygen 33% and halothane were used via a circle system. With controlled respiration at a fresh gas flow of 3-10 l.min-1, the expiratory cuff pressures of 10.1-16 cmH2O and the inspiratory cuff pressures of 23.4-32.4 cmH2O were below venous and arterial mucosal capillary perfusion pressures respectively. Cuff pressures were unaltered with time. Methylene blue instilled into the larynx did not appear in the trachea. Fifty-two control patients had the same incidence of sore throat (40%) and hoarseness (30%) at 24 h. With spontaneous ventilation, fresh gas flows of 5-15 l.min-1 maintained the cuff pressure above 10 cmH2O. We conclude that this valve prevents excessive tracheal cuff pressure while maintaining the airway seal.