Respiratory sinus arrhythmia in humans: how breathing pattern modulates heart rate

Area of Science:

• Physiology
• Cardiovascular Regulation
• Respiratory Physiology

Background:

• Respiratory sinus arrhythmia (RSA) reflects autonomic nervous system modulation of heart rate.
• Understanding RSA's relationship with breathing patterns is crucial for assessing cardiovascular health.

Purpose of the Study:

• To quantify the relationship between respiratory sinus arrhythmia amplitude (RSA) and breathing frequency and tidal volume.
• To characterize RSA patterns during both controlled and spontaneous breathing conditions.

Main Methods:

• Seventeen subjects controlled tidal volume and breathing frequency while breathing through a mouthpiece.
• Log-log plots of RSA versus breathing frequency were analyzed for different tidal volumes.
• Key parameters: low-frequency intercept (LFI), corner frequency (fC), and roll-off were determined.

Main Results:

• RSA amplitude showed a stable low-frequency intercept (LFI) below 6 cycles/min.
• At higher frequencies, RSA decreased with a constant roll-off slope above a corner frequency (fC).
• The RSA-tidal volume relationship was linear, allowing normalization of RSA-frequency curves.

Conclusions:

• LFI, fC, and roll-off effectively characterize an individual's RSA-frequency relationship.
• These characteristics hold true for both controlled and spontaneous breathing.
• Voluntarily synchronizing heart rate with breathing reduced RSA variability without altering mean RSA.