Two Operational Modes of Cardio-Respiratory Coupling Revealed by Pulse-Respiration Quotient.

Area of Science:

• Cardiovascular Physiology
• Respiratory Physiology
• Biomedical Engineering

Background:

• Breath-to-breath intervals (BBI) and R-R intervals (RRI) are not temporally concurrent.
• A novel method was previously developed to calculate the pulse respiration quotient (PRQ) accounting for this asynchrony.

Purpose of the Study:

• To investigate correlations between BBI and PRQ.
• To examine BBI correlations with mean RRI within each BBI (mRRI).
• To assess cardio-respiratory coupling under varying body postures and breathing patterns.

Main Methods:

• Analysis of BBI, RRI, and PRQ in 20 subjects across supine/standing positions and spontaneous/slow breathing.
• Calculation of linear regression slopes for BBI vs. PRQ and BBI vs. mRRI.
• Application of aggregation measures to identify cardio-respiratory coupling regimes.

Main Results:

• Positive correlations were observed between BBI and PRQ.
• Body posture, unlike breathing regime, significantly influenced BBI vs. PRQ linear regression slopes.
• Two distinct cardio-respiratory coupling patterns were identified based on BBI vs. mRRI scatter plots.
• R-pulse timing relative to respiration onset (using b1) indicated synchronization with sympathetic activation.

Conclusions:

• The proposed method effectively characterizes cardio-respiratory coupling.
• Body posture is a key factor influencing the relationship between respiration and heart rate variability.
• Identified coupling regimes and sympathetic activation patterns may have clinical relevance in pathological conditions.