Evaluation of an Adjustable Flow Diverter Valve for Mutiplex Ventilation: A Simulation Study

Abstract

Background: Ventilation of two patients with one machine during a ventilator shortage became a popular topic 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). Prior studies attempted to solve this problem by manipulating the resistance of the circuit to the patient requiring less V_T. But this method affects the total resistance of the system and changes volume delivery to both patients. We designed an adjustable flow diverter valve (AFDV) to partition flow without affecting the system resistance. The purpose of this study was to evaluate the performance of the AFDV.

Methods: Two IngMar ASL 5000 breathing simulators were set to represent identical passive 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 to each lung simulator was recorded by the simulators. The AFDV was adjusted from equal V_T to full occlusion of one patient. The AFDV was considered successful in individualizing V_T if volume delivery to patient A did not change while volume delivery to patient B decreased, as the valve was adjusted toward occlusion for patient B. In the full occlusion position, patient B was disconnected from the simulator to determine if there was disrupted ventilation to the other patient.

Results: The AFDV allowed precise control and nearly linear adjustments in volume delivery to one patient without impacting the other (see Figure). When the valve was adjusted for occlusion to patient B, this patient was successfully removed from the ventilator without affecting volume delivery to patient A and without ventilator alarms.

Conclusions: This simulation-based study shows that the AFDV allows individual control of the V_T to one patient without affecting ventilation to the other.

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