Data-Driven Estimation of Blood Pressure Using Photoplethysmographic Signals

Noninvasive measurement of blood pressure by optical methods receives considerable interest, but the complexity of the measurement and the difficulty of adjusting parameters restrict applications. We develop a method for estimating the systolic and diastolic blood pressure using a single-point optical recording of a photoplethysmographic (PPG) signal. The estimation is data-driven, we use automated machine learning algorithms instead of mathematical models. Combining supervised learning with a discrete wavelet transform, the method is insensitive to minor irregularities in the PPG waveform, hence both pulse oximeters and smartphone cameras can record the signal. We evaluate the accuracy of the estimation on 78 samples from 65 subjects (40 male, 25 female, age 29 +/- 7) with no history of cardiovascular disease. The estimate for systolic blood pressure has a mean error 4.9 +/- 4.9 mm Hg, and 4.3 +/- 3.7 mm Hg for diastolic blood pressure when using the oximeter-obtained PPG. The same values are 5.1 +/- 4.3 mm Hg and 4.6 +/- 4.3 mm Hg when using the phone-obtained PPG, comparing with A&D UA-767PBT result as gold standard. The simplicity of the method encourages ambulatory measurement, and given the ease of sharing the measured data, we expect a shift to data-oriented approaches deriving insight from ubiquitous mobile devices that will yield more accurate machine learning models in monitoring blood pressure.