Design and characterization of a measurement system for monitoring pressure exerted by bronchial blockers: In vitro trials

Bronchial blockers (BBs) allow occluding the bronchial duct and collapsing the “dependent” lung in a number of thoracic surgery. The occlusion is obtained through a cuff that, inflated with a proper air volume, exerts a pressure, P_e, on the inner wall of the mainstem bronchus. In this work a measurement chain, based on two piezorestistive force sensors, was developed and calibrated to measure P_e exerted by six BBs, as a function of inflated volume on in vitro models (two latex ducts with diameters similar to the ones of the adult mainstem bronchi: 12mm and 15mm). P_e showed wide changes considering different BBs, and significantly increases with the decrease of the model´s diameter, at the same inflated volume. Lastly, the minimum occlusive volume (MOV) to sail the two models was estimated for each BB. These experiments were performed by applying a pressure difference across the cuff of 25cmH₂O, in order to simulate the worst condition in a clinical scenario. Results show that MOV depends on both the type of BB and the duct diameter. The knowledge of this volume allows estimating the minimum value of P_e exerted by BBs to avoid air leakage.