The HEV ventilator can be easily manufactured and integrated into the hospital environment to support COVID-19 patients.In light of the importance of the pressure monitoring, the HEV ventilator will target pressure controlled modes. This will include: PC–A/C (Pressure Assist mode), PC–A/C–PRVC (Pressure Regulated Volume Control) mode, PC-PSV (Pressure Support Ventilation mode) and in addition a basic mode of operation: CPAP (Continuous Pos-itive Airway Pressure). The HEV design also provides PEEP (Positive End-Expiratory Pressure), which is not a ventilatory mode in itself but is designed to support steady low positive pressure to the lungs to avoid alveolar collapse. The PC–A/C–PRVC option adjusts the ventilator to provide a set the tidal volume at the lowest possible airway pres-sure. In the case where the tidal volume is not achieved at a particular pressure setting, due to changes in the patient’s airway resistance or lung compliance; this can then be gradually adjusted. All modes will allow the patient, when capable, to take spontaneous breaths, and all modes will assist the breathing when the spontaneous breath is taken, apart from CPAP which is continuous pressure.
HEV is a fully specified ventilator system suitable for hospital use, both in and out of intensive care units (ICU), for both intubated and mask/non-invasive cases. The pressure controlled modes outlined above are prioritised in view of their importance for COVID-19 treatment2. The pneumatic concept of the ventilator, i.e. ventilation provided via a pressure buffer, is close to those employed in the Amadeus Ventilator (Hamilton, 1994). It allows a precise and safe pressure control and accurate monitoring of flow rates. The step-down pressure design via the buffer puts safety up-front in the design. In addition to the COVID-19 official emergency guidelines, clinical advice has guided the main ventilator choices, prioritising in particular precise and stable pressure delivery, the simplification of ventilation modes, attention to the trigger timings, and a straightforward and familiar interface for clinicians. The design is cheap, rapid and simple to construct and the design choices prioritise low cost, readily commercially available components. The functionality is aimed at the treatment of the vast majority of COVID-19 cases. The availability of HEV as a ventilator option could free up the very high-end machines for the most intensive cases.
It is the goal of HEV to achieve a fully functional device which may be medically approved on a very short timescale. We note however that HEV aims to build a fully specified system, targeting regulatory approval regarding rapidly manufactured ventilator systems. Approval in countries such as the EU, Switzerland, or the US would allow this ventilator to be built and proposed to hospitals, and is also a key step towards unlocking the potential for faster approval world-wide. The design is adaptable to a wide range of geographic deployment, with local implementation and part choices depending on local requirements. HEV can be parametrised to address local needs such as alternative gas supplies or auto-clavable rather than single use parts, needs which are kept in mind throughout the design.
The project is run by the HEV collaboration, a group of physicists and engineers affiliated with the High Energy Physics institute CERN in Geneva, Switzerland.
Conceptual design of the HEV - High Energy Ventilator
HEV Specification Standards
Throughout the design of HEV, issues such as the expected required performance, the safety and reliability are built into the thinking. Due to the mechanical concept of the system and the flexibility of the software design, there are some cases where we can build alarms, alerts, or safety mechanisms which go beyond the minimum specifications and guidelines. For the purposes, we arrange the description of the expected performance, safety, and alarm systems follow the next standards: