Tracheal tube leak test : is there inter-observer agreement ?

Although the leak test is recommended as a method of assessing the appropriate size of uncuffed endotracheal tubes for use in children, the reproducibility of this test has not been validated. Patients from newborn to ten years of age requiring tracheal intubation for elective surgery were studied. The endotracheal tube size was calculated using the formula: (age + 16) divided by 4 for patients > or = two years of age and at the discretion of the attending anaesthetist for patients < two years of age. After the induction of anaesthesia and administration of a nondepolarizing muscle relaxant, the patient's trachea was intubated and mid-tracheal placement was confirmed. Two of the three staff anaesthetists participating in the study assessed the leak pressure consecutively. Each participant performed a single leak determination. The leak pressure was determined as follows: the patient was supine with the head in a neutral position, fresh gas flowed into the breathing circuit at 5 L.min-1, a stethoscope was placed on the skin over the larynx and the pressure relief valve was completely closed. Pressure slowly increased in the breathing circuit until an audible leak occurred around the tracheal tube. The inter-observer difference was calculated in 212 patients. The absolute value of the difference between that of two observers increased as the mean leak pressure increased. However, the variation between observers expressed as a percent of the absolute measurement remained constant. An average variance in measurement of 38% was found at both low and high leak pressures. In conclusion, we found considerable variation between two experienced observers in assessing leak pressures.