BP Sensor

Wearable blood pressure sensors employ several technologies. Oscillometric wrist cuffs inflate against the radial artery and detect pressure oscillations as the cuff deflates—maximum oscillation amplitude indicates mean arterial pressure, with systolic and diastolic derived algorithmically. Pulse Transit Time (PTT) methods calculate BP from the delay between ECG R-wave and peripheral pulse arrival, based on the principle that higher blood pressure increases arterial stiffness and pulse wave velocity. Tonometry-based sensors apply gentle pressure to flatten the radial artery against underlying bone and measure transmitted pressure waveforms. Photoplethysmography (PPG)-based approaches analyze pulse waveform morphology to estimate BP. FDA clearance requires accuracy within ±5 mmHg average error and ±8 mmHg standard deviation per ANSI/AAMI/ISO 81060-2 standards. Wearable accuracy is affected by arm position, cuff placement, motion, and requires periodic calibration against validated reference devices.