Bronchoscopy in mechanically ventilated patients is performed by passing a bronchoscope through the endotracheal tube (ETT), which substantially increases airflow resistance and may compromise ventilation. Here, we quantify the nonlinear, flow-dependent resistance of ETTs with and without a bronchoscope by analyzing pressure–flow relationships across multiple tube–bronchoscope configurations. We find that with bronchoscope insertion, tube resistance increases with the inverse fifth power of the effective tube diameter, defined as the diameter of a circular tube with the same cross-sectional area as the remaining lumen. Using an intensive care ventilator in combination with an active lung simulator, we demonstrate that the increased resistance during bronchoscopy causes dynamic hyperinflation and intrinsic positive end-expiratory pressure (PEEP) buildup in volume-controlled modes, and reduced tidal volumes in pressure-controlled modes. Numerical simulations using a simple scaling law relating resistance to effective tube diameter accurately reproduce the observed impairments. This demonstrates that the impact of tube narrowing during bronchoscopy can be reliably predicted from ventilator settings and patient respiratory mechanics. We present a predictive model that allows clinicians to anticipate and manage ventilation impairments, supporting evidence-based selection of endotracheal tubes and bronchoscopes. In addition, we provide proof of principle that combining pressure-controlled ventilation with automatic tube compensation can fully prevent these impairments, pointing to a technically feasible solution to an underrecognized clinical problem.

BF, NB and CK are the inventors of a pending patent application (PCT/EP2023/074318; WO2024052339A1) related to the ATC ventilator described. The other authors declare no competing interests.

This study did not receive any funding.

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Raw data can be obtained from the corresponding author upon request. The program for predicting ventilation impairments is freely available under MIT license and can be downloaded via the open access repository (https://fabrylab.github.io/Bronchoscopy/)

https://fabrylab.github.io/Bronchoscopy/