Measurement of Vital Signs Using Lifelight® Remote Photoplethysmography: results of the VISION-D and VISION-V observational studies

Background: Detection of early changes in vital signs (VS) enables timely intervention; however, measurement of VS requires hands-on technical expertise and is often time-consuming. Contactless measurement of VS is beneficial to prevent infection, such as during the COVID-19 pandemic. Lifelight® is a novel software being developed to measure VS by remote photoplethysmography, based on video capture of the face via the integral camera on mobile phones and tablets. We report two early studies in the development of Lifelight.

Objectives: The objective of the VISION-D study (NCT04763746) was to measure respiratory rate (RR), pulse rate (PR) and blood pressure (BP) simultaneously using the current standard of care (SOC) manual methods and the Lifelight software, in order to iteratively refine the software algorithms. The objective of the VISION-V study (NCT03998098) was to validate the use of Lifelight software to accurately measure VS.

Methods: BP, PR, and RR were measured simultaneously using Lifelight, a sphygmomanometer (BP, PR) and manual counting of RR. Accuracy performance targets for each VS were defined from a systematic literature review of the performance of state-of-the-art VS technologies.

Results: The VISION-D dataset (17,233 measurements from 8585 participants) met the accuracy targets for RR (0.3 ± 3.6 [mean error ± SD] vs target of 2.3 ± 5.0; n=7462), PR (0.3 ± 4.0 vs 2.2 ± 9.2; n=10,214), and diastolic BP (−0.4 ± 8.5 vs 5.5 ± 8.9; n=8951); for systolic BP, mean error target was met but not SD (3.5 ± 16.8 vs 6.7 ± 15.3; n=9233). Fitzpatrick skin type did not affect accuracy. The VISION-V dataset (679 measurements from 127 participants) met all the standards: −0.1 ± 3.4 for RR; 1.4 ± 3.8 for PR; 2.8 ± 14.5 for systolic BP; −0.3 ± 7.0 for diastolic BP.

Conclusion: At this early stage in development, Lifelight demonstrates sufficient accuracy in the measurement of VS to support certification for a level 1 Conformité Européenne (CE) mark. As use of Lifelight does not require specific training or equipment, the software is potentially useful for the contactless measurement of VS by non-clinical staff in residential and home care settings. Work is continuing to enhance data collection and processing in order to achieve the robustness and accuracy required for routine clinical use.