Applications
PPG-Based Hypertension and Blood Pressure Monitoring
PPG enables cuffless blood pressure estimation through pulse transit time (PTT), waveform morphology analysis, and multi-parameter machine learning models.
How it works
Schematic summary of this guide. Waveforms are illustrative, not measured data.
The WHO estimates that 1.28 billion adults aged 30–79 have hypertension (WHO hypertension fact sheet). Conventional BP monitoring requires uncomfortable cuff occlusion, limiting frequency and compliance. PPG-based cuffless BP estimation has three primary approaches: PTT-based methods (exploit the inverse relationship between BP and pulse wave velocity), waveform feature-based methods (extract systolic/diastolic BP correlates from pulse amplitude, width, and morphological indices), and machine learning methods that directly learn the BP-PPG mapping from large calibrated datasets.
Individual calibration is the Achilles heel of PPG-based BP monitoring. The PTT-BP relationship varies substantially across individuals due to differences in arterial stiffness, vessel geometry, and impedance matching. A single-point calibration using a cuff measurement reduces error but drifts over hours as BP conditions change.
Samsung's Galaxy Watch blood pressure feature requires cuff calibration every 28 days and is not intended for diagnosis. The FDA requires clinical studies adhering to AAMI/ISO 81060-2, and no consumer PPG BP device has achieved FDA clearance for independent use without calibration. For how the wearable studies were designed and why trends are easier to defend than single readings, see this evidence review.
Frequently Asked Questions
Can PPG measure diastolic blood pressure accurately?
Diastolic BP is harder to estimate from PPG than systolic BP. Systolic BP correlates better with PTT and peak-related features.
How often does a PPG BP monitor need recalibration?
It depends on the device. Samsung asks Galaxy Watch users to recalibrate blood pressure against a cuff every 28 days.
Does physical activity affect PPG blood pressure estimation?
Yes. During exercise, BP and PTT change rapidly and the calibration curve shifts. Most PPG BP approaches are validated only for resting or low-activity measurements. Exercise BP from PPG wearables is not validated for clinical use.