Differential effects of the blood pressure state on pulse rate variability and heart rate variability in critically ill patients

Elisa Mejía-Mejía,Panayiotis A Kyriacou,Mohamed Elgendi,James M May

doi:10.1038/s41746-021-00447-y

Elisa Mejía-Mejía, Panayiotis A Kyriacou + Show 2 more

Open Access

https://doi.org/10.1038/s41746-021-00447-y

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Abstract

Heart rate variability (HRV) utilizes the electrocardiogram (ECG) and has been widely studied as a non-invasive indicator of cardiac autonomic activity. Pulse rate variability (PRV) utilizes photoplethysmography (PPG) and recently has been used as a surrogate for HRV. Several studies have found that PRV is not entirely valid as an estimation of HRV and that several physiological factors, including the pulse transit time (PTT) and blood pressure (BP) changes, may affect PRV differently than HRV. This study aimed to assess the relationship between PRV and HRV under different BP states: hypotension, normotension, and hypertension. Using the MIMIC III database, 5 min segments of PPG and ECG signals were used to extract PRV and HRV, respectively. Several time-domain, frequency-domain, and nonlinear indices were obtained from these signals. Bland–Altman analysis, correlation analysis, and Friedman rank sum tests were used to compare HRV and PRV in each state, and PRV and HRV indices were compared among BP states using Kruskal–Wallis tests. The findings indicated that there were differences between PRV and HRV, especially in short-term and nonlinear indices, and although PRV and HRV were altered in a similar manner when there was a change in BP, PRV seemed to be more sensitive to these changes.

Highlights

Heart rate variability (HRV), which is defined as changes in heart rate over time[1], is an indicator that is used to evaluate the activity of the cardiac autonomic nervous system (ANS) because of its relationship with the parasympathetic and sympathetic activity directed into the sinus node in the heart, which controls the heart rate[2,3]
Because of the relationship between pulse transit time (PTT) and blood pressure (BP) and the effects of PTT on pulse rate variability (PRV) measurements[13,14], the aim of this study was to evaluate the relationship between HRV and PRV measured from electrocardiographic signals (ECG) and PPG signals, respectively, obtained from critically ill patients with hypotension, hypertension, or normotension
It has been found that the measurement of HRV in real-life scenarios can be impaired by several conditions, especially because of the cumbersome instrumentation needed for the acquisition of the ECG signals, which has, to some extent, precluded the usefulness and acceptance of HRV as a tool for clinicians to diagnose and monitor diseases, and for larger public health applications[6]

Summary

Introduction

Heart rate variability (HRV), which is defined as changes in heart rate over time[1], is an indicator that is used to evaluate the activity of the cardiac autonomic nervous system (ANS) because of its relationship with the parasympathetic and sympathetic activity directed into the sinus node in the heart, which controls the heart rate[2,3]. HRV is measured using electrocardiographic signals (ECG), which represent the electrical activity generated by the heart conduction system[3,7], and standards of measurement have been established to align the methodologies used in HRV studies, in order to allow for comparisons among results[8]. In recent years, several studies have reported obtaining information similar to HRV from other signals that contain information related to the cardiac cycle, such as pulse waves. One technique that has attracted significant attention for detecting pulse-waverelated HRV, known as pulse rate variability (PRV), is photoplethysmography (PPG)[9], which is a noninvasive, simple, and inexpensive technique that utilizes optical principles to obtain the pulse wave from the microcirculation in peripheral tissue[10,11]

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