Rationalization of the selection of tracheal tubes.

The problems of selection of tracheal tubes, and the need for a rationale, are outlined. Tracheal tubes of 7.5 mm and 8.5 mm i.d. are recommended for female and male patients, respectively. Tracheal size was determined using high pressure-low volume cuffs as measuring devices. The average diameter of the cuff at seal point was 16.2 mm (SD 1.2 mm) for female, and 20.8 mm (SD 2.3 mm) for male patients. To provide a seal with low pressure-high volume cuffed tubes, cuff sizes of 20.5 mm and 27.5 mm are recommended for female and male patients, respectively. The mechanism of sealing with low pressure-high volume cuffs is reviewed.