everything you need to know about MIT OPEN EMERGENCY VEntilator
Background & Need
We are one of several teams who recognized the challenges faced by Italian physicians, and are working to find a solution to the anticipated global lack of ventilators. In the US alone, the COVID-19 pandemic may cause ventilator shortages on the order of 300,000-700,000 units (CDC Pandemic Response Plans). These could present on a national scale within weeks, and are already being felt in certain areas. An increase in conventional ventilator production is very likely to fall short and with significant associated cost (paywall warning).
Key Ventilation Specifications
Note changes to specifications with increased BPM and I:E ratios. Adjusting one of these parameters may influence the other, since at higher BPM, the tidal volume is usually decreased. Consult a clinician.
From the Clinical Guidance this document summarizes the minimum set of requirements for ventilation:
Patients must be under the management of a trained clinician.
The minimum controllable parameters in order to ventilate a patient include:
BPM (breaths per minute): between 8 – 40 BPM
Tidal Volume (TV) (air volume pushed into lung): between 200 – 800 mL based on patient weight
I/E Ratio (inspiratory/expiration time ratio): recommended to start around 1:2; best if adjustable between range of 1:1 – 1:4*
Assist Detection pressure. When a patient tries to inspire, they can cause a dip on teh order of 1 – 5 cm H2O, with respect to PEEP pressure (not necessarily = atmospheric).
Airway pressure must be monitored
Maximum pressure should be limited to 40 cm H2O at any time; Plateau pressure should be limited to max 30 cm H2O
The use of a passive mechanical blow-off valve fixed at 40 cm H2O is strongly recommended
Clinician require readings of plateau pressure and PEEP (refer to clinical documentation tab)
PEEP of 5-15 cm H2O required; many patients need 10-15 cmH2O
Failure conditions must permit conversion to manual clinician override, i.e. if automatic ventilation fails, the conversion to immediate ventilation must be immediate.
Ventilation on room air is better than no ventilation at all. Blending of oxygen and air gas mixture to adjust FiO2 is not important in an emergency scenario. It is certainly nice to have that ability and can easily be implemented with a oxygen / air gas blender that some hospitals already have.
Covid-19 can get aerosolized (airborne), so HEPA filtration on the patient’s exhalation is required or between the ventilator unit and the patient (at the end of the endotracheal tube) to protect clinical staff from certain infection. In-line HEPA filters can usually be purchased alongside manual resuscitator bags.
Heat and moisture exchanger should be used in line with the breathing circuit.
Failure conditions must result in an alarm.
This is a minimal requirement set for emergency use. Equipment designed for more regular use, even if for emerging markets, will require additional features to be used on a regular basis.
*Range determined based on several COVID-19 patients’ ventilator settings reported from Boston area ICUs