Objective: To compare directly measured pressures at the cuff/trachea interface that are associated with two different bronchial cuff designs and four different methods of bronchial cuff inflation suggested for use with one-lung ventilation.
Design: In vitro study.
Setting: Experimental laboratory in a university-affiliated hospital.
Interventions: The bronchial cuffs of two different endotracheal tubes were inflated using one of four different methods of determining the cuff volume and pressure necessary to "just seal" the bronchus and obtain lung separation; positive-pressure test, negative-pressure test, CO2 analysis, and a new test using an anesthesia ventilator. When each method predicted the "just-seal" state, the pressure at the cuff/bronchus interface as well as cuff inflation pressure and volume were recorded.
Measurements and main results: Although the new test was incompatible with the bronchial blocker, the other three tests all accurately predicted lung separation with the Univent, with no significant differences in pressures exerted on the trachea. However, when used with the double-lumen tube, the new test produced significantly lower measured parameters than the other inflation methods. CO2 analysis did not reliably predict bronchial seal with the double-lumen tube.
Conclusions: To achieve lung separation with the lowest pressure on the trachea, the new test is the most appropriate method for use with the double-lumen tube; however, the negative-pressure test appeared to be the easiest and fastest method for use with the bronchial blocker. Although the bronchial blocker was associated with lower pressures transmitted from the cuff to the trachea, the in vitro model cannot predict which bronchial cuff design would be superior in vivo.