Flow resistances of disposable double-lumen, single-lumen, and univent tubes

OBJECTIVE: To compare the airflow resistances of modern double-lumen, single-lumen, and Univent (Fuji Systems Corp; Tokyo, Japan) tubes. DESIGN: A laboratory bench study. SETTING: A university hospital laboratory. MEASUREMENTS: Pressure differentials (Pd) were measured across study tubes at 10 L/min airflow (V) increments from 0 to 60 L/min in a tracheal model. Coefficients of resistance k1 (linear) and k2 (nonlinear) were calculated for each tube by the method of least squares using the Rohrer equation Pd/V = k1 + k2V. Data were assessed by analysis of variance (ANOVA) for the effects of tube design, circumference, and manufacturer on k1 and k2. MAIN RESULTS: Calculated combined mean k1 and k2 were significantly lower for single-lumen tubes compared with double-lumen or Univent tubes. There were no significant differences for k1 values between double-lumen or Univent tubes. The values for k2 were significantly lower for double-lumen tubes compared with Univent tubes. The k2 values were significantly lower for Rusch (Duluth, GA) or Sheridan (Argyle, NY) double-lumen tubes compared with Mallinckrodt (St Louis, MO) double-lumen tubes. This difference was because of the Y-connectors of the Mallinckrodt tubes. CONCLUSIONS: Flow resistances of modern disposable double-lumen tubes are lower than commonly perceived. In most clinical situations, there will be no decrease in flow resistance when a Rusch or Sheridan double-lumen tube is replaced by a single-lumen tube.