Evaluation of an Auxiliary Volume Display for Multiplex Ventilation: A Simulation Study

Abstract

Background: Studies have investigated multiplex ventilation during the COVID-19 pandemic. Our previous study indicated failure of a multiplex circuit to ventilate patients with different lung mechanics in 67% of simulations (PMID: 32345741). Of the four safety problems that must be solved to safely ventilate two patients with one ventilator, individual tidal volume monitoring may be the most important. IngMar Medical designed a prototype auxiliary volume display (AVD-19) to display tidal volume delivery to two patients during multiplex ventilation. The AVD-19 is not currently approved for patient use. The purpose of this study was to evaluate the accuracy of the AVD-19.

Methods: Two IngMar ASL 5000 breathing simulators were set to represent identical patients (same resistance and compliance). The mode of ventilation was pressure control continuous mandatory ventilation with set-point targeting (PC-CMVs) as in our previous study. The volume delivery was changed to each simulator with an adjustable flow diverter valve. As the volume distribution between patients was changed, the tidal volume to each lung simulator was recorded by the simulators and compared to the volumes displayed on the AVD-19. The volumes displayed on the AVD-19 were manually corrected to body temperature and pressure saturated conditions (BTPS).

Results: The volume reading from the AVD-19 underestimates actual volume delivery with average error of -17%. However, ISO standard 80601-2-12 says that the accuracy of the delivered volume monitoring equipment shall be within ± 4.0 mL +15% for the actual delivered volume. Therefore, the accuracy range of the AVD-19 (-15 to -24%) was reasonable.

Conclusions: This simulation-based study shows that the AVD-19 can display individual tidal volumes during multiplex ventilation, but for best accuracy would require an adjustment to correct for the error: V_T dosage = desired (mL/kg) x ideal body weight x 0.83.

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