A Low-Cost Tonometer Alternative: A Comparison Between Photoplethysmogram and Finger Ballistocardiogram and Validation Against Tonometric Waveform

• Main Authors: Ghalib Muhammad Waqas Janjua, Dewar Finlay, Daniel Guldenring, Atta Ul Haq, James Mclaughlin
• Format: Article
• Language: English
• Published: IEEE 2019-01-01
• Series: IEEE Access
• Subjects: Augmentation index (AIx); finger ballistocardiogram (BPP); cuff-less blood pressure; electrocardiogram (ECG); photoplethysmogram (PPG); pulse wave velocity (PWV)
• Online Access: https://ieeexplore.ieee.org/document/8851144/

Hypertension is a silent killer and one-third of its sufferers are unaware of its presence. Tonometric devices, like SphygmoCor, Compilor etc., represent the gold standard in pulse wave velocity (PWV) and augmentation index (AIx) measurements which are limited by their high cost and operational accuracy. Here, we present an alternative technology that is low cost and may be suitable for the `wearable' setting. We undertook the comparisons of arterial waveforms obtained by photoplethysmogram (PPG) and finger ballistocardiogram (BPP) sensors which were then validated against a SphygmoCor tonometric device. Specifically, the agreement analysis of the augmentation, stiffness, reflection, elasticity, ejection elasticity and dicrotic reflection indexes showed that arterial distension waveform sensing using BPP sensor, has precision and accuracy similar to that of a SphygmoCor tonometric device whilst outperforming the volumetric arterial flow sensing using a PPG sensor, in every index. BPP indexes showed the r² fit of up to 0.95 and Spearman's rank correlation up to 0.91 when validated against the SphygmoCor tonometer. The estimated individual transfer functions for the BPP sensor, with reference to SphygmoCor, have accuracies of above 85% and 98% for 2 and 4-element windkessel (WK) models, respectively. The findings reported in this work may also be useful for the development of systems that are beneficial in the early and/or routine detection of hypertension.