Table 1. Key challenges in splitting ventilation.

A comparison of the capabilities of existing splitting mechanisms and iSAVE. *See fig. S9 for details regarding the rerouting of standard sensing metrics required for ventilator calibration and self-tests. PEEP, positive end-expiratory pressure; FiO₂, fraction of inspired oxygen; ΔC, change in compliance; ΔR, change in resistance; P_plat, plateau pressure.

Concern	Uniform splitting (pressure control mode)		iSAVE (volume control mode)
Individualized management of ventilation
- PEEP	x	Shared between patients	o	Individualized to each patient
- Tidal volume	x	Shared between patients	o	Individualized to each patient
- FiO2, respiratory rate	x	Shared between patients	x	Shared between patients
- Alarms	x	Changes to one patient’s status may not result in main ventilator alarm	o	Changes to one patient’s status will cause main ventilator to alarm. Mechanical components to provide auditory alarms can be incorporated
Sudden changes to patient status can cause damaging rebalancing of airflow to other patient(s) toward most compliant lungs	x	Ventilation cannot be quickly adjusted	o	Can be managed by titrating flow control valves. One-way valves prevent backflow. Pressure release valves prevent excess pressure delivery
Improvement or deterioration of one patient (ΔC, ΔR) will automatically rebalance airflow, potentially harming other patient(s)	x	Ventilation cannot be individually rebalanced. Patients would need to be re-matched as they improve/deteriorate	o	Desired ventilation for each patient can be achieved through valve adjustment, allowing patients to improve/deteriorate while remaining on the same system.
Abruptly removing patients requires breaking the circuit, causing aerosolization of the virus, exposing healthcare personnel	x	Individual patient circuits cannot be quickly removed from circuit	o	Individual patients can be quickly shunted/removed from the circuit. Inline filters limit aerosolization risk
Monitoring	x	Additional respiratory monitors and heightened clinical vigilance required	x	Additional respiratory monitors and heightened clinical vigilance required
Measurement of pulmonary mechanics	x	Shared between patients	o	Pplat can be measured using expiratory hold button. C, R can be computed for each patient
Ventilator calibration/self-test	x	Added circuit volume defeats the operational self‐test	o	Can be executed with modifications to circuit*
Triggering	x	Disabled. Patients will require sedation	x	Disabled. Patients will require sedation