Accepted for/Published in: JMIR Biomedical Engineering
Date Submitted: Oct 9, 2019
Date Accepted: Mar 1, 2020
Validation of Contact-free, Ballistocardiography Based Emfit QS in Measuring Nocturnal Heart Rate and Heart Rate Variability
ABSTRACT
Background:
Heart rate (HR) and heart rate variability (HRV) measurements are widely used in the monitoring of stress and recovery status among sedentary people and athletes. However, effective HRV monitoring should be daily basis because sparse measurements do not bring forth the complete view about the stress and recovery balance. Morning electrocardiography (ECG) measurements with HR straps are time-consuming and arduous to perform every day and thus compliance with regular measurements is poor. Contact-free, ballistocardiography (BCG) Emfit QS is effortless for daily basis monitoring. However, to the best of our knowledge, there is no study relating the accuracy of nocturnal HR and HRV measuring from BCG under real-life conditions.
Objective:
The aim of this study was to evaluate the accuracy of BCG based Emfit QS in measuring nocturnal HR and HRV.
Methods:
Twenty, healthy participants completed nocturnal HR and HRV recordings at home using BCG based Emfit QS and ECG based reference device (Firstbeat BG2) during sleep. Emfit QS measures BCG by under a bed mattress installed ferroelectret sensor. HR and the square root of the mean squared differences of successive R-R intervals (RMSSD) were determined for 3 min epochs and the mean of the sleep period.
Results:
The small mean bias were observed in the mean HR (-0.8 ± 2.3 bpm) and Ln RMSSD (-0.05 ± 0.25 ms) between Emfit QS and ECG. In addition, very large correlations were found in the mean values of HR (r = 0.90) and Ln RMSSD (r = 0.89) between the devices. The greater amount of erroneous or missing data was found in the Emfit measurements (28.3 ± 14.4%) compared with the reference (1.1 ± 2.3%). The results showed that 5.0% of the mean HR and Ln RMSSD values were outside the limits of agreement.
Conclusions:
Based on the present results, Emfit QS provides nocturnal HR and HRV data with the acceptable small mean bias, when the values are determined as the mean of the sleep period. Thus, Emfit QS seems to be a potential tool for long term monitoring of nocturnal HR and HRV. However, further researches are needed to clarify reliability in HR and HRV detecting.
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