Arterial stiffness estimated from the PPG pulse wave parameter b/a showed >300% variation at nonoptimal probe contact pressures, compared to high repeatability (CV <5%) at optimal contact pressure.
Observational (n=5)
Does optimal probe contact pressure improve the repeatability of arterial stiffness estimation using photoplethysmography in healthy subjects?
Optimal probe contact pressure is crucial for reliable and repeatable estimation of arterial stiffness using photoplethysmography.
Currently, photoplethysmography (PPG) is a frequently studied optical blood pulsation detection technique among biophotonic and biomedical researchers due to the fact that it shows high potential for estimating the arterial stiffness (AS). The extraction of diagnostically useful information requires standardized measurement procedure with good repeatability. However, the effects of a crucially important factor-the optimal contact pressure (CP) of the probe-are often ignored. Also, CP values are not reported to evaluate those effects. It is hypothesized that AS estimated from PPG pulse wave 2nd derivative parameter b/a is strongly inconsistent when recorded at nonoptimal probe CP. Our pilot study confirmed this during in vivo PPG recordings from conduit artery sites on five healthy subjects at variable probe CP (0 to 15 kPa) by using 880 nm reflectance type sensor, force transducer, and PPG alternating current (AC) signal pulse area derived optimal CP criterion. The b/a values, calculated from PPG with variable CP, showed variation >300 percent. In contrast, at the optimal CP, the b/a showed high repeatability (coefficient of variability <5 percent). The effect has been explained with exponential pulse pressure-volume relationship model which indicates the optimal CP range.
Grabovskis et al. (2013) conducted an observational in Healthy subjects (n=5). Variable probe contact pressure vs. Optimal contact pressure was evaluated on PPG pulse wave 2nd derivative parameter b/a. Arterial stiffness estimated from the PPG pulse wave parameter b/a showed >300% variation at nonoptimal probe contact pressures, compared to high repeatability (CV <5%) at optimal contact pressure.