HEV ventilator design
The HEV ventilator was designed for easy manufacturing and integration into the hospital environment to support COVID-19 patients. In light of the importance of the pressure monitoring, the HEV ventilator targets pressure controlled modes. This includes: 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 Positive 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 tidal volume at the lowest possible airway pressure. If the tidal volume is not achieved at a particular pressure setting, due to changes in the patient’s airway resistance or lung compliance; the pressure can then be gradually adjusted to achieve the set volume. 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 treatment. The pneumatic concept of the ventilator is based on ventilation provided via a pressure buffer. 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, which are a list of guidelines provided by MHRA, AAMI and WHO, 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 low cost, 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.
Internal UPS (allows autonomous use of the system for more than 20 minute).
PC–A/C: Pressure Assist mode
PC–A/C–PRVC: Pressure Regulated Volume Control
PC-PSV: Pressure SupportVentilation
CPAP: Continuous Positive Airway Pressure
PEEP: Positive End-Expiratory Pressure, is supplied for all modes
Human interface: touch screen.