Thinking about breathing: Effects on respiratory sinus arrhythmia.

Area of Science:

• Cardiovascular Physiology
• Respiratory Physiology
• Autonomic Nervous System Function

Background:

• Respiratory sinus arrhythmia (RSA) is the variation in heart rate (HR) with breathing.
• RSA is typically assessed as a function of breathing frequency (f).
• A better understanding of RSA's role in gas exchange efficiency is needed.

Purpose of the Study:

• To investigate whether RSA correlates better with breathing-specific heart rate (HR/f) or breathing frequency (f).
• To determine if RSA is a mechanism for optimizing cardio-respiratory coupling and gas exchange.

Main Methods:

• RSA was measured breath-by-breath in 209 participants.
• Measurements were taken during spontaneous and volitional breathing at various frequencies.
• Heart rate (HR) and breathing frequency (f) were recorded.

Main Results:

• RSA showed a stronger linear correlation with HR/f than with f in both spontaneous and volitional breathing.
• Increased HR/f was associated with increased RSA.
• RSA did not significantly differ between spontaneous and volitional breathing when analyzed by HR/f.

Conclusions:

• Breathing-specific heart rate (HR/f) is a more accurate reflection of cardio-respiratory coupling than breathing frequency (f) alone.
• RSA appears to be a central mechanism that improves the synchronization of pulmonary blood flow and airflow.
• This mechanism functions independently of the ventilatory drive source (autonomic or cortical).