Towards Corroborating the Arterial Stiffness with Lyfas Optical Biomarkers: A Novel Study

¹ Department of Research and Development (Digital Health), Acculi Labs Pvt. Ltd., Bangalore 560098, Karnataka, India

^*Corresponding Author

Subhagata Chattopadhyay

Department of Research and Development (Digital Health)

Acculi Labs Pvt. Ltd.

Bangalore 560098, Karnataka

India

Email: subhagata.chattopadhyay2017@gmail.com

Phone Number: +919972774547

Abstract

Background: Vascular aging (VA) increases the risk of Cardiovascular Disease (CVD) and premature deaths. Increased VA is attributed to the extent of the Arterial stiffness index (ASI), which is evident in smokers, diabetics, hypertensives, etc. The authors of this paper have discussed the usage of a smartphone-based healthcare instrument, called Lyfas that works with the principle of arterial photoplethysmography (APPG) and estimates the Pulse rate variability (PRV), which surrogates for the Heart rate variability (HRV) and its correlated digital cardiovascular biomarkers (CVb). PRV reflects cardiovascular autonomic modulation, which helps obtain the ASI by Lyfas.

Objective: To establish the inter-relationships of the CVb and ASI using Lyfas.

Methods: (i) Lyfas assess the ASI from the 2nd derivative of the photoplethysmography (SDPPG) waveform of the capillary arteriole at the tip of index fingers using the camera sensor. From SDPPG, ASI is computed. (ii) Lyfas simultaneously captures the CVb such as SDNN, RMSSD, HR, HRV score, pNN50, SD1/SD2, and LF/HF. (iii) Linear regressions (LR) and One-way ANOVA, and Pearson’s interclass correlations (‘r’) are applied to check the interrelationships of (a) ASI with that of (b) CVb in 116 adults (58 females and males, each) within the age group of 30-60 years and above. Hypersensitivity of Lyfas has been tested by taking the test thrice a day at a gap of 8 hours. The variance and the ranges are measured for hypersensitivity analysis.

Results: The study found that the ranges and variances fall within the normal limits. For female hypertensives, SDNN and LF/HF are statistically significant to predict for ASI with correlation (r) values of 0.79 in the age group >60 years and -0.98 in the age group 41-50 years and 0.99 in the age group 41-50 years, respectively. In the case of smokers, SD1/SD2 is negatively correlated (-0.77) with ASI and is statistically significant. male smokers, RMSSD, and HRV are statistically significant to predict for ASI with correlation (r) values of 0.59 in the age group 30-40 years and 0.96 in the age group 41-50 years and for HRV 0.96 in the age group 41-50 years, respectively. In the case of hypertensives, SDNN is negatively correlated (-0.89) with ASI in the age group of 41-50 years and is statistically significant. No biomarker showed a significant correlation in diabetics in this sample.

Conclusions: Lyfas is a robust clinical-grade instrument and the CVb captured by it can predict the ASI and the vascular age in a personalized manner.

Keywords: Lyfas; Cardiovascular biomarkers; Arterial Photoplethysmography; Arterial Stiffness Index; Second Derivative Photoplethysmography; Vascular age

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