M2 blood pressure monitor

Small (maximum dimension ~5 cm, mass <100 g) diaphragm pumps capable of pumping to pressures in the range of 40 kPa or more with flow rates in the range of 1 L min⁻¹are readily available and suitable for this application. Since these pumps are not reversible, a solenoid valve must be used to rapidly vent air from the system, releasing the applied pressure.
Figure 2 shows a schematic view of the pneumatic system, a design identical to that used in many commercial blood pressure meters, and comprising a diaphragm pump (Parker-Hanniffin corporation T5-1IC-03-1EEB, Ohio, USA), solenoid valve (912-000007-005), and a blood pressure cuff connector from an Omron M2 blood pressure monitor (Omron Corporation, Tokyo, Japan).
Figure 3 shows a top view of the partially assembled data-logger base unit. The Omron air hose connector can be seen below the main PCB (grey plastic).

To collect medium-term HRV data, participants will wear a Fitbit Charge 5 smartwatch for a total of 6 weeks. The HRV-B itself will be conducted using a Polar H10 chest strap for 10 min two times per day. This connects via Bluetooth to the Elite HRV smartphone app, which is downloaded to participants’ phones. Participants will aim to increase their HRV score as displayed in Elite HRV in real time using a diaphragmatic breathing technique (figure 1). Omron M2 blood pressure monitor (endorsed by the British Hypertension Society) will be used to conduct NLT in clinic and the adapted Autonomic Profile (aAP).27 (link)