Cuffless blood pressure estimation based on haemodynamic principles: progress towards mobile healthcare

• Published in: PeerJ (San Francisco, CA) CA), 2021-05, Vol.9, p.e11479-e11479, Article e11479
• Main Authors: Yamakoshi, Takehiro, Rolfe, Peter, Yamakoshi, Ken-Ichi
• Format: Article
• Language: English
• Subjects: Accuracy; Analysis; Antihypertensives; Bioengineering; Blood pressure; Calibration; Cardiology; Drugs and Devices; Global Health; Haemodynamic principle; Human-Computer Interaction; Hypertension; Methods; Mobile health; Modified normalized pulse volume; Smart phones; Smartphone; Smartphones; Variables
• ISSN: 2167-8359; 2167-8359
• DOI: 10.7717/peerj.11479

Although cuff-sphygmomanometry is used worldwide in medical and healthcare fields, it is a fact that the use of an occlusive cuff to obtain blood pressure ( ) is troublesome and inconvenient. There have therefore been on-going efforts to devise methods that do not require the use of a cuff, almost all being based on the measurement of pulse wave velocity or pulse transit time, but so far few significant developments have been made, especially regarding measurement accuracy. We have previously reported a smartphone-based cuffless method using a linear multiple regression calibration model comprising of obtained with a cuff-sphygmomanometer as an objective variable and modified normalized pulse volume ( : a measure of vasoconstrictive activity in a finger) and pulse rate ( ) as explanatory variables. This requires a number of subjects to construct a calibration model and thus is largely dependent on the accuracy due to the model. To address these drawbacks, we report here a new cuffless method to surpass considerably the results of our previous study as well as earlier works. With this method we can estimate , with much higher accuracy, using and , both also obtained from a smartphone-derived photoplethysmogram. The subject firstly performs a cuff-based measurement in parallel with the acquisition of and from a smartphone. These parameters are set as initial values ( , and ; initial calibration procedure). Then, the estimated ( ) can be calculated from the relation: " = ( · · )/( · )", which is derived from the so-called haemodynamic law. To validate this method, preliminary experiments using 13 volunteers were carried out to compare results from the new method with those from the cuff-sphygmomanometry, used as a reference. Altogether 299 paired data sets were analyzed: A good agreement was found between the cuff-based and the estimated values, with correlation coefficients of 0.968 for systolic ( ), 0.934 for mean ( ) and 0.844 for diastolic ( ). analyses for the ( , , ) and the ( , , ) values also supported these comparison results. Mean absolute differences between the and the values in total subjects were less than 5 mmHg. Fairly good tracking availability in terms of time series data of the against the corresponding values was also confirmed in each subject during the study periods (1-2 weeks for 12 subjects and about 4 months for one subject). The present study reported the successful development of the new cuffless estimation method, given as the stat