Assessing the Quality of Heart Rate Variability Estimated from Wrist and Finger PPG: A Novel Approach Based on Cross-Mapping Method

Abstract

The non-invasiveness of photoplethysmographic (PPG) acquisition systems, together with their cost-effectiveness and easiness of connection with IoT technologies, is opening up to the possibility of their widespread use. For this reason, the study of the reliability of PPG and pulse rate variability (PRV) signal quality has become of great scientific, technological, and commercial interest. In this field, sensor location has been demonstrated to play a crucial role. The goal of this study was to investigate PPG and PRV signal quality acquired from two body locations: finger and wrist. We simultaneously acquired the PPG and electrocardiographic (ECG) signals from sixteen healthy subjects (aged 28.5 ± 3.5, seven females) who followed an experimental protocol of affective stimulation through visual stimuli. Statistical tests demonstrated that PPG signals acquired from the wrist and the finger presented different signal quality indexes (kurtosis and Shannon entropy), with higher values for the wrist-PPG. Then we propose to apply the cross-mapping (CM) approach as a new method to quantify the PRV signal quality. We found that the performance achieved using the two sites was significantly different in all the experimental sessions (p < 0.01), and the PRV dynamics acquired from the finger were the most similar to heart rate variability (HRV) dynamics.

Multimodal Assessment of the Pulse Rate Variability Analysis Module of a Photoplethysmography-Based Telemedicine System

“…Therefore, it is important to assess the agreement between HRV and PRV under different (physiological and pathological) conditions in order to confidently accept the PPG-based PRV-analysis as a reliable alternative to monitor HRV changes. So far, several studies have compared PRV to the gold standard of ECG-derived HRV [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. Some publications found good agreements between PRV and HRV, especially in younger subjects and at rest [ 31 , 57 ], or during sleep [ 58 ], and mostly in time-domain parameters.…”

“…Moreover, this implies that PRV parameters may bear additional information about cardiovascular functioning, which is not available in HRV indices. Disparities between HRV and PRV have already been studied by several researchers, and various HRV and PRV indices have been reported to highly correlate in healthy individuals [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. However, most of these studies are restricted to selected HRV parameters and resting healthy conditions.…”

Estimation of heart rate variability from finger photoplethysmography during rest, mild exercise and mild mental stress

“…Some studies claim that finger PPG signal is cleaner than signals from wrist PPG [ 24 ]. But to our extent of knowledge, there is only a few studies that have assessed the different location of the PPG sensor when estimating HRV [ 25 , 26 ]. One of them assessed the signal quality and found waveforms from finger PPG to have higher quality than waveforms from the wrist.…”

“…The second study compared HRV features derived from finger and wrist and compared it with HRV features from ECG. They found the performance from wrist and finger PPG to be significantly different in favor of finger PPG [ 25 ]. Also, the Shimmer sensors we used are only compatible with measurements on the finger and earlobe.…”

A Review of Deep Learning-Based Contactless Heart Rate Measurement Methods

“…Typically, 10 electrodes of the ECG machine are attached to different parts of the body including the wrist and ankle. Different from ECG, PPG-based medical devices possess differing sensor shapes placed on different parts of the body such as rings, earpieces, and bands [ 7 , 11 , 12 , 13 , 14 , 15 , 16 ], and they all use a light source and a photodetector to detect the PPG signal with signal processing, see Figure 1 . The signal processing is for the purpose of processing the reflected optical signal from the skin [ 1 ].…”