Development and Evaluation of a System to Ventilate 2 Patients With a Single Ventilator

Concerns over ventilator shortages during COVID-19 led to a number of potential solutions including using one ventilator for multiple patients. Large scale peer to peer military operations could create similar shortages. We developed and tested a device to allow 2 patients to be ventilated with a single, currently deployed ventilator.

Limitations of previous designs were reviewed and design requirements detailed. An accessory device capable of splitting gas flow to 2 patients was created with separate settings for peak inspiratory pressure (PIP) and positive-end expiratory pressure (PEEP). Monitoring of airway pressures and volumes delivered to each patient were also provided along with high and low alarms. Respiratory rate, inspiratory time, inspired oxygen concentration, and rise time settings were shared and identical for each simulated patient. All breaths were pressure control (PC) breaths. Bench testing on a test lung capable of separate adjustments for compliance and resistance was accomplished across the operational range. Airway pressures and volumes delivered to each lung were continuously measured using a flow and pressure monitor and recorded for analysis.

The device provided individualized setting of PIP and PEEP for each patient across the ventilator's range to account for variations in lung mechanics and ventilatory requirements. The delivered VT to patient "B" was within 10% of the target in all conditions tested. The delivered VT to patient "A" was within 10% of the target in 21 of 22 conditions tested and within 15% in all conditions. Ti was the most important shared setting with respect to delivering the target VT to either patient. Disconnection of either patient resulted in similar reductions to VT in the companion patient, while obstruction and suctioning caused markedly different effects on the VT, PIP, and PEEP delivery to the companion patient.

An accessory to a deployed ventilator allowed for independent delivery of PIP, tidal volume and PEEP across a clinically relevant range of values in the face of large differences in lung compliance and resistance between simulated patients. The complexity of the system provides monitoring and overcomes previously identified limitations. However, implementation of such a system is limited by regulatory requirements and training concerns.