Abstract 12960: Differential Pulse Arrival Time: A Novel Approach to Continuous Cuff-less Blood Pressure Monitoring

Abstract

Introduction: Blood pressure (BP) is a continuous and dynamic physiologic variable. The sphygmomanometer has forced clinicians to rely on singular snapshots of BP to make clinical decisions about BP control. Ambulatory cuff-based BP monitoring has demonstrated superiority over the conventional, single-point office-based cuff measurement and has unveiled the important concept of nocturnal BP dipping; however, it is plagued by poor compliance leading to limited use. Thus, there is an unmet need for an unobtrusive continuous ambulatory BP monitor. Current methods for continuous, non-invasive ambulatory BP monitoring include the use of vascular unloading and pulse transit time. However, both of these techniques have limitations. We therefore propose a novel method—differential pulse arrival time (DPAT)—to continuously estimate BP non-invasively. We hypothesized that continuous DPAT-derived BP correlates well with cuff-based measurement of BP at rest and during a cold-pressor maneuver. Methods: Normotensive subjects were fitted with a DPAT device and a Finapres Nova ambulatory BP monitor. Each subject underwent a standardized protocol consisting of 2 minutes at rest, 2 minutes cold pressor at 40 o F, and 2 minutes at rest. The raw data from the DPAT device was then time-matched and compared with the Finapres BP trend. Results: Over 100 million DPAT data points were collected from 12 normotensive subjects (age range 20-50). DPAT correlated with Finapres blood pressures with a correlation coefficient of 0.8 and there was no evidence of bias on Bland-Altman plot. (Figure 1). The root mean square error for the predicted blood pressure was ±4.76 mmHg for systolic BP and ±4.03 mmHg for diastolic BP. Conclusions: Differential pulse arrival time obtained by an optical-sensor based system is a viable approach to monitoring continuous BP in normotensives. Future studies in elderly, hypertensive individuals are warranted.