Diverter Valve and Volume Display for Ventilating Two Patients with One Ventilator-Simulator Based Performance Evaluation (1090-003710) (Research Abstract Professor Rounds: Group 3)
Start time: Thursday, January 28, 2021, 11:30 AM End time: Thursday, January 28, 2021, 12:30 PM Session Type: Research Abstracts (Completed Studies)
The COVID-19 pandemic has created an overwhelming demand for mechanical ventilators. This demand has stimulated much interest in using one ventilator for multiple patients called multiplex ventilation [1-4]. Many have posted methods for this on the Internet, but there is little supporting evidence and no human studies. Multiplex ventilation is associated with risk because the method, as described in the literature, results tidal volumes and PEEP levels that are largely uncontrollable and depend on the difference between patient resistance, (R) and compliance (C). The purpose of our simulation-based study was to determine the feasibility of controlling volume distribution from one ventilator to two patients using prototypes of a flow diverter valve and a dual pneumotachometer.
Two patients were simulated with two separate breathing simulators (ASL 500, IngMar Medical, Pittsuburgh, PA). Two lung models were created with resistance of 10 cm H2O/L/s and compliance of 45 mL/cm H2O) simulating mild ARDS. They were ventilated using parallel patient circuits with a Servo-I ventilator (Getinge, Rastatt, Germany) using pressure control with total volume to the two patients = 800 mL. A prototype flow diverter valve was 3-D printed. Adjustment of the device progressively occluded one inspiratory limb of the circuit while maintaining total cross sectional area of the combined dual patient circuits. This allowed reduction of tidal volume for one patient while maintaining a constant tidal volume for the other. We also designed and tested a small dual pneumotachometer to monitor the tidal volumes. Measurement error was defined as (pneumotachometer measured volume – simulator measured volume)/simulator measured volume, expressed as %.
The flow diverter valve had settings displayed as 10 equal marks around the circumference of the device indicating arbitrary amounts of outflow occlusion. Figure 1 shows that as the valve was adjusted through the range of 10 settings, tidal volume delivery to patient B decreased in a highly linear fashion while tidal volume delivery to patient A was held constant. The dual pneumotachometer showed a mean (SD) error for Patient A of -19% (2%) and for patient B of -23% (3%).
The prototype flow diverter valve demonstrated the feasibility of multiplex ventilation when patient needs differ enough to require controllable, unequal volume delivery. It allowed easy partitioning of the total volume delivered by the ventilator to two simulated patients, ranging from equal distribution to total occlusion of one patient (eg, when disconnection of the patient is necessary). The prototype dual pneumotachometer demonstrated that an inexpensive device based on disposable, commercially available flow sensors underestimated the true volumes but was accurate enough for emergency use. These two devices, if commercially available, would make multiplex ventilation safe enough for emergency use in the dire situation of ventilator shortage.