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