Pressure and volume changes in tracheal tube cuffs during anaesthesia

Recently, it has been observed that, when a patient is breathing a nitrous oxide-oxygen mixture and the cuff of the tracheal tube is filled with air, nitrous oxide may diffuse into the cuff and thereby cause an increase in volume and pressure. In the present investigation, different gas mixtures were used to fill the cuff, and repeated measurements of pressure, and occasionally of volume, were made during anaesthesia. Both large-volume and small-volume cuffs were studied. A considerable increase in volume and pressure took place in both types of cuffs. The changes were directly proportional to time for the first few hours. If the cuff was inflated with nitrous oxide-oxygen, no pressure increase occurred, and this was also true for the air-filled cuff if halothane anaesthesia was given.