Well, math concepts, and more. In “Human sigh acts as a reset button” (Discovery News, Tuesday, 11 May 2010), Larry O’Hanlon says:
Scientists studying breathing patterns think they have found the reason we sigh: To reset breathing patterns that are getting out of whack and keep our respiratory system flexible.
The re-setter hypothesis is based on the idea that breathing is an inherently dynamic and rather chaotic system, with all sorts of internal and external factors changing how much oxygen we need and keeping our lungs healthy and ready for action.
This sort of system requires a balance of meaningful signals and random noise to operate correctly.
Occasional noise in a physiological system, like the respiratory system, is essential because it enables the body to learn how to respond flexibly to the unexpected, says Vlemincx.
“A sigh can be considered a noise factor because it has a respiratory volume out of range,” she says.
So in times of stress, when breathing is less variable, a sigh can reset the respiratory system and loosen the lung’s air sacs, or alveoli, which may be accompanied by a sensation of relief, says Vlemincx.
© 2014 ABC
Makes sense that breathing has a lack of pattern, just as our heart rate does — hence the importance of HRV. Maybe we need to work on something called RV: respiratory variability. Use some Poincare plots, and more, to study the variations, to find out what is healthy and unhealthy. Must be some nervous system correlates in breathing, too, just as in heart rate.