Individualized System for Augmenting Ventilator Efficacy (iSAVE): A Rapidly deployable system to expand ventilator capacity

Shriya Srinivasan; Khalil Ramadi; Franceso Vicario; Declan Gwynne; Alison Hayward; Robert Langer; Joseph Frassica; Rebecca Baron; Giovanni Traverso

Benchtop testing protocol 1) Check for leaks and alarms: We first tested the ability of the system to perform ventilation without leaks. We then disconnected a lung to ensure the activation of standard alarms on the ventilator. 2) Variable tidal volume production: Starting with both flow valves fully open, we measured the flow and pressure delivered to each lung. Then, we gradually closed one of the valves, measuring the distribution of flow, to map the range of volume distribution capable of the system. 3) Maintenance of VT following static changes to compliance and resistance: Patient interdependencies in the circuit pose a major challenge for the multiplexing approach of ventilation. As a patient degenerates or recovers, changes in tissue compliance and resistance occur. These cause shifts in the overall circuit's flow dynamics. We modulated the compliance and/or resistance of one test lung, measured the effect of the intervention, and titrated the valve until the baseline parameters were reached. Resistors (Rp5, Rp20, Rp50 and Rp500 Michigan Instruments) were utilized for all benchtop testing. We performed these tests with baseline parameters set to those of 1) a healthy lung (C = 50 cmH20, Rp5) 2) a lung with ARDS (C = 20 cmH20, Rp5-50). While the flow valve was the main variable we modulated, in some cases, the ventilator's tidal volume or inspiration : expiration ratio was also adjusted. These cases are specifically mentioned in the results section. 4) Maintenance of VT following dynamic changes to compliance and resistance. Sudden deterioration of a patient (blood clot, pneumothorax) or equipment malfunction (kinked endotracheal tube) pose great risk to the balance of ventilation between patients. We tested the ability of the iSAVE to manage these scenarios. We simulated acute changes by disconnecting or clamping tubes and monitoring the ventilator's response. The flow valves were also titrated to return the circuit to its baseline.