From the Guidelines
Heart Rate Increase During Inspiration
Heart rate increases during inspiration in patients with spontaneous breathing due to respiratory sinus arrhythmia, which is modulated by cardiac parasympathetic (vagal) outflow 1.
- This phenomenon is characterized by an increase in heart rate during inspiration and a decrease during expiration, resulting from mechanically induced changes in transthoracic pressure produced by rhythmic respiratory activity 1.
- The fluctuations in heart rate are also associated with changes in blood pressure, cardiac output, and total peripheral resistance 1.
- In healthy individuals, the heart rate variability during deep breathing is typically greater than 15 beats per minute in those aged over 50 years 1.
- The increase in heart rate during inspiration is a normal physiological response, and its magnitude can vary depending on factors such as age and underlying cardiovascular health 1.
From the Research
Heart Rate Increase during Inspiration
The increase in heart rate during inspiration in patients with spontaneous breathing can be attributed to several factors, including:
- Respiratory sinus arrhythmia (RSA), which is the increase and decrease in instantaneous heart rate with inspiration and expiration 2
- Sympathetic hyperreactivity and baroreceptor dysfunction, which can lead to increased heart rate variability during spontaneous breathing 3
- The effect of breathing on heart rate variability, which can be influenced by the type of ventilatory drive (cortical or autonomic) 2
Mechanisms of Heart Rate Increase
The mechanisms underlying the increase in heart rate during inspiration include:
- Cardio-respiratory coupling, which is the matching between pulmonary blood flow and intermittent airflow 2
- Baroreceptor gain, which can be higher in patients with spontaneous periodic breathing, leading to increased sympathetic outflow and heart rate variability 3
- Parasympathetic nerve activity, which can be inhibited by consciously controlled breathing, leading to a decrease in the high-frequency component of heart rate variability 4
Effects of Breathing on Heart Rate Variability
The effects of breathing on heart rate variability include:
- Increased heart rate and decreased high-frequency component of heart rate variability during controlled breathing 4
- Parallel changes in muscle sympathetic nerve activity and heart rate variability during select acute stressors, such as exercise and hypoxia 5
- Caution is warranted when using heart rate variability as a marker of sympathetic activity, as it may not always change in parallel with muscle sympathetic nerve activity 5