The Physiological Sigh: What Is It And How You Can Benefit

The physiological sigh is a natural and often automatic deep breathing technique that has been shown to have numerous benefits for our physical and mental well-being. In this article we will delve into the neuroscience behind this remarkable phenomenon, outline its various benefits, and provide a step-by-step guide on how to harness the power of the physiological sigh.

The Neuroscience of the Physiological Sigh

Basic physiology
The physiological sigh is a natural and automatic breathing pattern characterized by a deep inhale, followed by a secondary, shorter inhale, and a slow exhale. This type of breathing occurs spontaneously in humans and animals, especially during periods of rest, sleep, or stress. The primary function of the physiological sigh is to regulate the respiratory system, specifically by re-inflating the small air sacs called alveoli in the lungs, which are responsible for gas exchange and oxygenation of the blood (1).

The role of the preBötzinger complex in the brainstem
The preBötzinger complex, located in the brainstem, plays a crucial role in generating the physiological sigh. This cluster of neurons controls the rhythmic patterns of our breathing, including the natural occurrence of sighs. When the brain senses a decrease in blood oxygen levels or an increase in stress, it sends signals to the preBötzinger complex, which then triggers the physiological sigh to help restore balance within the respiratory system (2).

The release of neuropeptides and their effects on stress and mood
The act of deep breathing during a physiological sigh stimulates the release of neuropeptides, such as oxytocin and vasopressin, which have been linked to stress reduction and mood regulation. Research has shown that these neuropeptides can have a calming effect on the nervous system and may play a role in promoting relaxation, reducing anxiety, and enhancing overall emotional well-being (3).

Benefits of the Physiological Sigh

Reducing anxiety and stress
The physiological sigh has been shown to effectively reduce anxiety and stress levels. By stimulating the release of neuropeptides and regulating the autonomic nervous system, this deep breathing technique helps promote relaxation and a sense of calm. Studies have demonstrated that nasal respiration, which is emphasized in the physiological sigh, can significantly reduce stress and anxiety by entraining human limbic oscillations (4).

Enhancing focus and mental clarity
The physiological sigh can also improve focus and mental clarity by increasing oxygen levels in the brain. Deep breathing helps deliver more oxygen to the brain, allowing it to function more efficiently. Research has shown that slow, deep breathing can shift the autonomic nervous system's balance, leading to enhanced cognitive function and improved mental performance (5).

Improving lung function and oxygenation
The primary function of the physiological sigh is to regulate lung function by re-inflating the alveoli, the small air sacs responsible for gas exchange in the lungs. By promoting the efficient exchange of oxygen and carbon dioxide, the physiological sigh can help improve lung function and overall oxygenation of the blood, which is essential for maintaining good health (6).

Promoting relaxation and sleep
The physiological sigh has been found to be beneficial in promoting relaxation and improving sleep quality. Paced breathing, which involves slow, deep breaths similar to those in the physiological sigh, has been shown to enhance vagal activity, leading to better sleep quality and reduced insomnia symptoms (7).

Boosting mood and emotional regulation
The physiological sigh has a positive impact on mood and emotional regulation by promoting the release of neuropeptides such as oxytocin and vasopressin. These neuropeptides have been shown to improve overall emotional well-being by reducing stress, promoting relaxation, and enhancing the ability to regulate emotions effectively (8).

Step-by-Step Guide to the Physiological Sigh

1. Finding a comfortable and quiet space. To practice the physiological sigh effectively, it is essential to find a comfortable and quiet space where you can focus on your breathing without distractions. This could be a designated meditation corner, your bedroom, or even a peaceful outdoor spot.
2. Adopting a relaxed posture: Adopt a relaxed posture, either sitting or lying down, with your spine straight and shoulders relaxed. Ensure that your body is well-supported and comfortable to help maintain focus on your breathing throughout the practice.
3. Inhaling deeply through the nose: Begin by taking a slow, deep inhale through your nose, allowing your chest and abdomen to expand as you fill your lungs with air. Focus on the sensation of the breath entering your nostrils and filling your lungs.
4. Adding a second, shorter inhale on top of the first: After the initial deep inhale, take a second, shorter inhale through your nose to further fill your lungs. This second inhale is a key component of the physiological sigh, helping to maximize the re-inflation of the alveoli in your lungs.
5. Exhaling slowly through the mouth: After the second inhale, exhale slowly through your mouth, allowing your chest and abdomen to contract as you release the air from your lungs. Focus on the sensation of the breath leaving your body and the relaxation that accompanies it.
6. Repeating the process as needed: Repeat the physiological sigh breathing pattern as needed, typically for several minutes or until you feel a sense of calm and relaxation. It is essential to maintain focus on your breath throughout the practice, observing the sensations that accompany each inhale and exhale.

By understanding the science behind the physiological sigh and incorporating it into our daily routines, we can access its potential benefits for stress reduction, mental clarity, lung function, relaxation, and emotional regulation. Remember to practice the physiological sigh in a comfortable, quiet space with a relaxed posture, inhaling deeply through the nose, adding a second, shorter inhale, and exhaling slowly through the mouth. Repeating this process as needed can help improve overall well-being and enhance our ability to cope with the challenges of daily life.

References:
(1) Feldman, J. L., Del Negro, C. A., & Gray, P. A. (2013). Understanding the rhythm of breathing: so near, yet so far. Annual Review of Physiology, 75, 423-452.
(2) Lieske, S. P., Thoby-Brisson, M., Telgkamp, P., & Ramirez, J. M. (2000). Reconfiguration of the neural network controlling multiple breathing patterns: eupnea, sighs and gasps. Nature Neuroscience, 3(6), 600-607.
(3) Yackle, K., Schwarz, L. A., Kam, K., Sorokin, J. M., Huguenard, J. R., Feldman, J. L., ... & Krasnow, M. A. (2017). Breathing control center neurons that promote arousal in mice. Science, 355(6332), 1411-1415.
(4) Zelano, C., Jiang, H., Zhou, G., Arora, N., Schuele, S., Rosenow, J., & Gottfried, J. A. (2016). Nasal respiration entrains human limbic oscillations and modulates cognitive function. Journal of Neuroscience, 36(49), 12448-12467.
(5) Jerath, R., Edry, J. W., Barnes, V. A., & Jerath, V. (2006). Physiology of long pranayamic breathing: Neural respiratory elements may provide a mechanism that explains how slow deep breathing shifts the autonomic nervous system. Medical Hypotheses, 67(3), 566-571.
(6) Bloch-Salisbury, E., Shea, S. A., Brown, R., Evans, K., & Banzett, R. B. (1996). Air hunger induced by acute increase in PCO2 adapts to chronic elevation of PCO2 in ventil
2 patients. Journal of Applied Physiology, 81(2), 949-956.
(7) Tsai, H. J., Kuo, T. B. J., Lee, G. S., & Yang, C. C. H. (2015). Efficacy of paced breathing for insomnia: Enhances vagal activity and improves sleep quality. Psychophysiology, 52(3), 388-396.
(8) Russo, M. A., Santarelli, D. M., & O'Rourke, D. (2017). The physiological effects of slow breathing in the healthy human. Breathe, 13(4), 298-309.