Novel method for non-invasive blood pressure measurement from the finger using an optical system based on dynamic light scattering

摘要

Self-measurement of blood pressure (BP) is important for monitoring treatment of hypertension, but current instrumentsare cumbersome and at times also impractical, especially for the older population. Current optical solutions, such asPPG-based technologies that were developed for improving convenience, provide derived measurements that are ofteninaccurate, particularly for diastolic values. Alternatively, by using dynamic light scattering (DLS) we are able tomeasure the direct hemodynamic response. We propose a simple physical model that explains the relation betweenarterial pressure values and the hemodynamic response which is measured from the finger root following changes inexternally applied pressure. Based on this model we have developed a small-scaled, optical, mobile device thatmeasures BP at the finger using dynamic light scattering. The apparatus is positioned at the base of the index finger andcontains a ring with an inflatable cuff with two miniaturized dynamic light scattering (mDLS) sensors situated distal tothe cuff. The cuff is inflated to above systolic pressure, and changes in blood flow (hemodynamics) are measuredduring cuff deflation. BP measurement is carried out using specially designed algorithms based on hemodynamicindexes and waveform analysis which capture systolic and diastolic points in real-time. Using this apparatus, wemeasured BP from 69 patients visiting a hypertension outpatient clinic, and a control group of 15 healthy subjects. BPreadings were compared with measurements recorded at the arm location with an Omron device used in the clinic. Themean absolute error (MAE) for systolic and diastolic blood pressure was 7.8 and 9 mmHg, respectively at all ranges ofBP measured. In conclusion, using Elfi-Tech's innovative technology, it is possible to measure BP accurately at thefinger location using a compact, convenient mDLS-based device with high accuracy.