Accuracy of heart rate variability estimated with reflective wrist-PPG in elderly vascular patients

Abstract

Optical heart rate monitoring (OHR) with reflective wrist photoplethysmography is a technique mainly used in the wellness application domain for monitoring heart rate levels during exercise. In the absence of motion, OHR technique is also able to estimate individual beat-to-beat intervals relatively well and can therefore also be used, for example, in monitoring of cardiac arrhythmias, stress, or sleep quality through heart rate variability (HRV) analysis. HRV analysis has also potential in monitoring the recovery of patients, e.g. after a medical intervention. However, in order to detect subtle changes, the calculated HRV parameters should be sufficiently accurate and very few studies exist that asses the accuracy of OHR derived HRV in non-healthy subjects. In this paper, we present a method to estimate beat-to-beat-intervals (BBIs) from reflective wrist PPG signal and evaluated the accuracy of the proposed method in estimating BBIs in a cross-sectional study with 29 hospitalized patients (mean age 70.6 years) in 24-h recordings performed after peripheral vascular surgery or endovascular interventions. Finally, we evaluate the accuracy of more than 30 commonly used HRV parameters and find that the accuracy of certain metrics, for example SDNN and triangular index, shown in the literature to be associated with the deterioration of the status of the patients during recovery from surgical intervention, could be adequate for patient monitoring. On the other hand, the parameters more affected by the high-frequency content of the HRV and especially the LF/HF-ratio should be used with caution.

Effectiveness of the heartbeat interval error and compensation method on heart rate variability analysis

“…In addition, the relative error of SD1 is larger than SD2. These results support the results obtained in the literatures [15,20].…”

“…Recently, PPI is also widely used to obtain heart rate in wearable sensors instead of RRI, because it is easier to measure in daily life. However, Reference [15] states that the PPI increases relative error of some of the indices such as LF/HF and SD1/SD2. Reference [20] also shows that the use of PPI increases the error of HF and SD1.…”

“…Previous studies [12][13][14] FIGURE 1 Concept image of this study have demonstrated that the effect of interval errors on HRV analysis when using pulse intervals obtained from PPG is limited, and the error using PPG is negligible when the patient is at rest. Reference [15] evaluate HRV indices using PPG with 29 hospitalized patients and the paper pointed out that some of the indices affected by the high-frequency content of the HRV. These studies have been evaluated using data with a sampling rate of 125 Hz or higher.…”

Signal-to-noise ratio is more important than sampling rate in beat-to-beat interval estimation from optical sensors

“…Bent and Dunn plan to include recordings under physical activity, and thus variable signal quality in future works [28]. Our own previous work has also shown that signal quality of PPG recorded from patients using wearable devices is quite volatile, and the quality of PRV derivation highly depends on both the specific PRV parameter and the individual patient [39]. However, none of the comparable works did systematically consider SNR so far.…”

Long-Short Ensemble Network for Bipolar Manic-Euthymic State Recognition Based on Wrist-worn Sensors

“…The standard deviation of the NN intervals (SDNN) [7] was also calculated. Note that popular features such as RMSSD [7] and LF/HF ratio [7] were not considered as they are particularly noisy when computed from a PPG signal [15]. Consequently, the feature set extracted for the HRV is as follows:…”