The relationship among bronchial blocker cuff inflation volume, proximal airway pressure, and seal of the bronchial blocker cuff

The resting volume and diameter of the bronchial blocker cuff (defined as inflation of the cuff to just its natural shape) of the Univent (Fuji Systems Corp, Tokyo, Japan) tube are 2 mL and 5 mm. However, much larger inflation volumes may be required to seal an adult mainstem bronchus and the surface area of contact between the resultant spherical or ellipsoid-shaped cuff and the wall of the mainstem bronchus may be small and susceptible to leak with the application of high proximal airway pressures. This experiment determined the relationship among airway diameter, proximal airway pressure, inflation volume of the bronchial blocker cuff, and leakage of air around the bronchial blocker cuff in an in vitro model. The experimental model consisted of silicon tubing of 12.8-, 16.0-, and 19.2-mm ID as the mainstem bronchus. The main tracheal cuff sealed the Univent tube into the proximal end of the mainstem bronchus and the bronchial blocker cuff was inflated with various volumes near the distal end of the mainstem bronchus. The space between the tracheal cuff and the bronchial blocker cuff was then progressively pressurized in either a static or pulsed manner. The very distal end of the bronchus was functionally submerged under a beaker of water so that a bronchial blocker cuff leak would be indicated by bubbling. It was found that the Univent bronchial blocker cuff sealed the 12.8- and 16.0-mm ID mainstem bronchi against airway pressures as great as 100 cmH 20, with inflation volumes that were within the manufacturer's recommendation of 6 to 7 mL. Clinically, there was little difference in the cuff volume required to seal the bronchial blocker cuffs of the 6.0- and 9.0-mm ID Univent tubes against static and pulsed proximal airway pressures of the same magnitude. If an intraoperative leak develops, then intra-cuff volume should be increased to 6 to 7 mL and, if the leak is still present, then the surgeon may need to rearrange the surgical field so that the relationship between the mainstem bronchus (a cylinder) and the bronchial blocker cuff (a sphere or ellipsoid shape) is no longer distorted.