Objective: One promising approach for a continuous, noninvasive, cuff-less ambulatory blood pressure (BP) monitor is to measure the pulse wave velocity or the inversely proportional pulse transit time (PTT), based on electrical and optical physiological measurements in the chest area. A device termed IsenseU-BP+ has been developed for measuring continuous BP, as well as other physiological data. The objective of this paper is to present results from the first clinical evaluation with a wide range of patients. The study was set up to verify whether IsenseU-BP+ can be used to measure raw signals with sufficient quality to derive PTT. Methods: The test protocol, run 23 times on 18 different patients with nonalcoholic fatty liver disease, includes both supine measurement at rest as well as measurements during indoor cycling. Changes in PTT were compared with the BP changes measured using validated reference sensors. Results: IsenseU-BP+ measured signals with good quality during rest on 17 of 18 patients despite the high diversity in age, body shape, and body mass index. Evaluation during cycling was difficult due to a lack of good reference measurements.
Conclusion: IsenseU-BP+ measures PTT with high quality during supine rest and exercise and could therefore be suitable for deriving noninvasive continuous BP, although evaluation during exercise was limited due to inaccurate reference BP measurements.
Significance: Continuous, noninvasive measurement of BP would be highly beneficial in a number of clinical settings. Systems currently considered as the gold standard for the investigation of hypertension carry considerable limitations, which could be overcome by the method proposed here.