Validation of the Lifelight Contactless Blood Pressure and Pulse Rate Monitor (Preprint)

Abstract

BACKGROUND Key to reducing the immense morbidity and mortality burdens of cardiovascular diseases is helping people keep their blood pressure at safe levels. This requires that more people with hypertension be identified, diagnosed and given the tools to lower their blood pressure. Blood pressure monitors are critical to hypertension diagnosis and management. However, there are characteristics of conventional blood pressure monitors (oscillometric cuff sphygmanometers) that hinder their ability to facilitate rapid and effective hypertension diagnosis and management. Lifelight is a novel, calibration-free, software-only medical device that contactlessly measures pulse rate and blood pressure by measuring remote photoplethysmography (rPPG) signals of a patient’s face using a standard smartphone or tablet camera. OBJECTIVE Demonstrate the accuracy of Lifelight for classifying the full range of clinically relevant blood pressures as hypertensive or non-hypertensive. Demonstrate its accuracy for measuring pulse rate and the blood pressure of people with blood pressures relevant to Stage 1 hypertension. METHODS Lifelight was investigated in a study that followed the data collection and data analysis methodology outlined in ISO 81060-2:2018/AMD 1:2020 “Non-invasive Sphygmomanometers – Part 2: Clinical investigation of automated measurement type”. This validation study was conducted by independent laboratory Element Materials Technology Boulder (formerly Clinimark), a global leader for clinical testing of vital sign data for medical devices and consumer wearable products. The study generated data from 85 people aged 18-85 with the wide-ranging distribution of blood pressures specified in ISO 81060-2:2018/AMD 1:2020. At least 20% were required to have Fitzpatrick scale skin tones of 5 or 6, i.e., dark skin tones. The accuracy of Lifelight’s blood pressure measurements was assessed by comparing Lifelight’s measurements with measurements made by dual-observer manual auscultation using the same-arm sequential method specified in ISO 81060-2:2018/AMD 1:2020. The accuracy of Lifelight’s pulse rate measurements was assessed by comparing Lifelight’s measurements with concurrent ECG-derived heart rate values. RESULTS Lifelight measured pulse rate with Accuracy root-mean-square of 1.34 beats per minute. The sensitivity and specificity with which Lifelight determined that blood pressures exceeded the in-clinic systolic threshold for diagnosis of hypertension was 70.1% and 71.7%, respectively. These rates are consistent with those reported for conventional blood pressure monitors in a literature review by The National Institute for Health and Care Excellence (NICE). The mean error of Lifelight for measuring blood pressure in the range of normotension and Stage 1 hypertension (i.e., in 65 of the 85 study participants) was 6.48 ± 12.88 mmHg for systolic blood pressure, and 0.43 ± 10.64 mmHg for diastolic blood pressure. No device-related adverse events occurred. CONCLUSIONS Lifelight has been independently tested against ISO 81060-2:2018/AMD 1:2020. Its safety and performance demonstrated in this study suggests that it is a promising solution for rapid, scalable and effective screening and management of hypertension.