Characteristics of Double-Lumen Tubes Determine Bronchial Airway Pressure

To determine pressure-flow characteristics of double-lumen tubes (DLTs) with an outer diameter of 26 to 41 French and calculate bronchial pressure in a model setup and using data from patients who underwent one-lung ventilation with a DLT.

Prospective experimental study and retrospective analysis of clinical measurements.

University medical center.

Lung model and patients.

Flow rates and pressure gradients across Robertshaw-type DLTs (∆P(DLT)) were measured in a physical model and the DLT-specific resistance coefficients were calculated from ∆P(DLT) according to Rohrer's approach. Bronchial pressure was calculated from airway pressure and ∆P(DLT) in a lung model and using data from 72 patients who underwent thoracic surgery and direct bronchial pressure measurements.

∆P(DLT) increased with decreasing outer diameter of the DLT and more than doubled during one- compared with two-lung ventilation (p<0.001). ∆P(DLT) differed between inspiration and expiration (p<0.05) and was higher across the tracheal lumen compared with the bronchial lumen (p<0.001). Root mean square differences between calculated and measured bronchial pressures were less than 0.7 cmH2O in the lung model and less than 1.2 cmH2O in the clinical measurements.

The DLTs' pressure-flow characteristics differed considerably depending on size, mode of ventilation (one or two lung), direction of flow, and lumen for ventilation. Rohrer's approach allowed for sufficient calculation of the bronchial airway pressure during both one- and two-lung ventilation.