Leakage of disposable breathing circuits

Abstract

Study Objective: To determine the sites and rates of the leakage of disposable breathing circuits. Design: Nonclinical, experimental study. Setting: Experimental laboratory. Interventions: To identify in vitro the leakage sites by bubble test and to measure the leakage rate by the increased oxygen (O 2) flow needed to maintain the circuit pressure provided by an anesthesia machine previously verified to have no leaks. Breathing circuit pressures measured with a sphygmomanometer of 30, 50, 70, and 100 mmHg were studied. Measurements and Main Results: Ninety-seven disposable and three reusable breathing circuits from seven manufacturers were investigated for leakage. There was a linear relationship between the circuit pressure and O 2 fl ow at which leaks occurred. No leakage was detected in reusable circuits at 30 mmHg of circuit pressure. Leakage was found in two of the six junctions between the patient adapter and the corrugated tubing in the reusable breathing circuits at a circuit pressure of 100 mmHg. In 90% of the disposable circuits tested, the leakage rate was less than 75 ml/min at 30 mmHg of circuit pressure, but there was a wide variation in the amount of leakage among the circuits of different companies. Almost all the leakage sites were located at connections in the circuit and not in the corrugated tubing. The most common site of leakage in the disposable circuits was the junction between the patient adapter end and the corrugated tubing (57%) rather than the swivel piece (40%). Conclusions: Most disposable breathing circuits can be used safely for closed-circuit anesthesia, as the leakage volume is too small to be of clinical importance. The variation in the leakage rates stresses the importance of quality control of the connector seals.