Temporal Stability of Resting Respiratory Sinus Arrhythmia: Choosing the Quantification Method

Respiratory sinus arrhythmia (RSA) is defined as heart rate variability (HRV) synchronised with respiration, characterized by heart rate increase during inspiration and heart rate decrease during expiration. Accurate and robust quantification of resting RSA is crucial, as it serves as a reliable and noninvasive biomarker of emotion regulation capacity. This is important for its application in prediction and diagnosis of various psychopathological conditions, as well as objectivized assessment of protective traits like stress resilience. In this paper, we describe and compare several different methods for quantifying resting RSA. Our evaluation, conducted on a sample of university students (N=34) across two test sessions, separated by a minimum of one week, revealed that a novel method based on the time-domain concordance correlation coefficient (TCCC) outperformed others. This method demonstrated highest temporal stability, with an intraclass correlation coefficient (ICC) of 0.79, and was less susceptible to changes in respiratory parameters. The proposed method and experimental evaluation contribute to the establishment of a standardized approach for resting RSA quantification, with potential application in diverse fields.