Statistical strategies to quantify respiratory sinus arrhythmia: Are commonly used metrics equivalent?

An index of Level I can be derived from quantifying respiratory sinus arrhythmia, a periodic component of beat-to-beat heart rate variability that is synchronous with spontaneous breathing and a valid index of cardiac vagal tone via ventral vagal pathways.

“An index of Level I can be derived from quantifying respiratory sinus arrhythmia, a periodic component of beat-to-beat heart rate variability that is synchronous with spontaneous breathing and a valid index of cardiac vagal tone via ventral vagal pathways (Lewis et al., 2012).”

The effect of respiratory depth or tidal volume on HRV accounts for less than 5% of the variance in several measures of HRV but more than 10% when using the peak-to-trough method.

“However, the effect of respiratory depth or tidal volume on HRV has been shown to account for less than 5% of the variance in the several measures of HRV but more than 10% of the variance when using the peak-to-trough method (Lewis et al., 2012).”

Different indices of HRV are differentially affected by breathing, with the peak-to-trough method being most affected.

“(1) different indices of HRV are differentially affected by breathing with the peak-to-trough method being most affected (e.g., Penttila et al., 2001; Hill et al., 2009; Lewis et al., 2012);”

When analyzed appropriately, even measures derived from the peak-to-trough method can be reliable indicators of HRV without additional respiratory control.

“(2) when analyzed appropriately, even measures derived from the peak-to-trough method can be reliable indicators of HRV without additional respiratory control (Lewis et al., 2012);”

Peak-valley analysis acts as a time-domain filter dynamically centered at the exact ongoing respiratory frequency.

“such as the peak-valley analysis (Grossman et al., 1990), also known as peak-to-trough analysis (Lewis et al., 2012), which acts as a time-domain filter dynamically centered at the exact ongoing respiratory frequency (Grossman et al., 1990).”

Vagal cardioinhibitory pathways support homeostatic functions.

“There is a large literature documenting that the amplitude of respiratory sinus arrhythmia (RSA), a valid index of cardiac vagal tone [17], is related to positive clinical outcomes (e.g., Ref. [18]).”

The Porges-Bohrer method provides an opportunity to study the dynamically changing amplitude of RSA independently of a potential nonstationary baseline representing dynamic changes in heart rate.

“Unlike other methods, the Porges-Bohrer method [17,63,64] provides an opportunity to study the dynamically changing amplitude of RSA independently of a potential nonstationary baseline representing dynamic changes in heart rate.”

Compared to peak-to-through and spectral analysis methods, the Porges adaptive filter method was significantly more sensitive to vagal mechanisms, with effect sizes more than 3 times greater, as evidenced through glycopyrrolate infusion.

“compared to the other two methods, the Porges adaptive filter method was significantly more sensitive to vagal mechanisms (effect sizes were reported as more than 3 times greater than the other two methods) as evidenced through a glycopyrrolate infusion.”

The frequency band (.12-.40 Hz) used in the Porges adaptive filter method to define RSA in adults can accurately capture respiration rates, with less than 1% of individual breaths falling outside this band.

“the frequency band (.12–.40 Hz) used in the Porges adaptive filter method to define RSA in adults can accurately capture respiration rates (less than 1% of individual breaths fell outside this frequency band).”