Table 1 Key challenges in splitting ventilation.

A comparison of the capabilities of existing splitting mechanisms and iSAVE. PEEP, positive end-expiratory pressure; FiO2, fraction of inspired oxygen; ΔC, change in compliance; ΔR, change in resistance; Pplat, plateau pressure.

ConcernUniform splitting (pressure control mode)iSAVE (volume control mode)
Individualized management of ventilation
-PEEPx Shared between patientso Individualized to each patient
-Tidal volumex Shared between patientso Individualized to each patient
-FiO2, respiratory ratex Shared between patientsx Shared between patients
-Alarmsx 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
rematched 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
health care 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.
Monitoringx Additional respiratory monitors and
heightened clinical vigilance required
x Additional respiratory monitors and
heightened clinical vigilance required
Measurement of pulmonary mechanicsx Shared between patientso Pplat can be measured using expiratory hold
button. C and R can be computed for each
patient.
Ventilator calibration/self-testx Added circuit volume defeats the operational
self-test.
o Can be executed with modifications to circuit*
Triggeringx Disabled. Patients will require sedation.x Disabled. Patients will require sedation.

*See fig. S9 for details regarding the rerouting of standard sensing devices required for ventilator calibration and self-tests.