Airway Ventilation Pressures During Bronchoscopy, Bronchial Blocker, and Double-Lumen Endotracheal Tube Use: An In Vitro Study

Objective: To quantify inspiratory flow resistance of instrumented single-lumen and double-lumen endotracheal tubes. Design: Bench-top in vitro experiments. Setting: Laboratory of a university hospital. Participants: In vitro lung simulator. Interventions: A lung simulator was ventilated mechanically via several single- and double-lumen endotracheal tubes (ETT) that were instrumented with adult and pediatric bronchoscopes as well as bronchial blockers. While ventilating with a square-flow wave and increasing peak inspiratory flow from 10-100 L/min, the pressures proximal and distal to the instrumented ETT were measured. Flow (Q) and the pressure loss (Delta P) were related with regression of the quadratic equation: Delta P = k(1)Q + k(2)Q(2). Measurements and Main Results: With all combinations of single-lumen endotracheal tubes, double-lumen endotracheal tubes, bronchial blockers, and adult and pediatric bronchoscopes, Delta P was accurately related to Q using the quadratic equation with excellent fit, R-2 > 0.99 for all combinations. The regression parameters k1 and k2 were statistically significant for all combinations except k1 with a bronchoscope through 37-Fr double-lumen endotracheal tube. Parameter k2 was dominant at flows above 10 L/min for uninstrumented airways and 20 L/min for instrumented airways. Delta P increased dramatically with flow, and increased with decreasing endotracheal tube size or addition of instrumentation in a quantitatively predictable manner. Conclusions: Pressure loss across instrumented endotracheal tubes follows a predictable flow-dependant quadratic pattern. Using the quantitative in vitro results of this study, a clinician can maximize inspiratory ventilation pressures during these situations without delivering excessive airway pressures to the patient. (C) 2014 Elsevier Inc. All rights reserved.