Abstract
SummaryBackgroundThe manufacturing of any standard mechanical ventilator cannot rapidly be upscaled to several thousand units per week, largely due to supply chain limitations. The aim of this study was to design, verify and perform a pre-clinical evaluation of a mechanical ventilator based on components not required for standard ventilators, and that met the specifications provided by the Medicines and Healthcare Products Regulatory Agency (MHRA) for rapidly-manufactured ventilator systems (RMVS).MethodsThe design utilises closed-loop negative feedback control, with real-time monitoring and alarms. Using a standard test lung, we determined the difference between delivered and target tidal volume (VT) at respiratory rates between 20 and 29 breaths per minute, and the ventilator's ability to deliver consistent VT during continuous operation for >14 days (RMVS specification). Additionally, four anaesthetised domestic pigs (3 male-1 female) were studied before and after lung injury to provide evidence of the ventilator's functionality, and ability to support spontaneous breathing.FindingsContinuous operation lasted 23 days, when the greatest difference between delivered and target VT was 10% at inspiratory flow rates >825 mL/s. In the pre-clinical evaluation, the VT difference was -1 (-90 to 88) mL [mean (LoA)], and positive end-expiratory pressure (PEEP) difference was -2 (-8 to 4) cmH2O. VT delivery being triggered by pressures below PEEP demonstrated spontaneous ventilation support.InterpretationThe mechanical ventilator presented meets the MHRA therapy standards for RMVS and, being based on largely available components, can be manufactured at scale.FundingWork supported by Wellcome/EPSRC Centre for Medical Engineering,King’s Together Fund and Oxford University.
Highlights
Early during the Covid-19 pandemic, invasive mechanical ventilation was employed extensively to treat respiratory failure.[1]
Design verification testing Design verification testing against the rapidly manufactured ventilator systems (RMVS) specification was performed in volume controlled ventilation (VCV) mode using three identical test lungs of fixed resistance 20 cmH2O/(L/s) and compliance 17.7 mL/cmH2O
To investigate system lifetime under high-flow rates, a single unit was set to operate at tidal volume (VT) = 600 mL, Respiratory rate (RR) = 27/min, I:E ratio = 1:2, Positive end-expiratory pressure (PEEP) = 10 cmH2O and pressure limit (Plimit) = 45 cmH2O until failure
Summary
Background Early during the Covid-19 pandemic, invasive mechanical ventilation was employed extensively to treat respiratory failure.[1] In response to an anticipated shortage in intensive care ventilation capacity due to exceptional demand, the UK Government launched the Ventilator Challenge, seeking both conventional and novel designs of ventilator systems that could be manufactured at scale within a few weeks This shortage provided an important justification for seeking novel designs, which could be manufactured outside of impacted supply chains
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