JOIN USThe University of Leuven in Belgium study found that sighing resets the breathing patterns, keeping our lungs healthy and ready for action, the Discovery News reported.
The research looked at eight men and 34 women with sensor-equipped shirts that recorded their breathing, heart rates and blood carbon dioxide levels over 20 minutes of quiet sitting.
The researchers, who looked for specific changes over one-minute period encompassing sighs, found that there were different breathing patterns before and after a sigh that confirmed the "re-setter hypothesis" for the function of sighing.
"Our results show that the respiratory dynamics are different before and after a sigh. We hypothesise that a sigh acts as a general re-setter of the respiratory system," Elke Vlemincx and her co-authors write in the latest issue of the journal Biological Psychology.
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.
According to Vleminc, 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.
"A sigh can be considered a noise factor because it has a respiratory volume out of range," Vlemincx told Discovery News.
In this experiment, a sigh was defined as at least two times as large as the mean breath volume.
"A breath is defined by a specific volume (depth), the amount of air we breathe in and out, and a specific timing, the time it takes to breathe in and out," Vlemincx said.
"Both these characteristics vary: from one moment to the next we breathe slower, faster, shallower, deeper."
Vlemincx explained that when breathing is in one state for too long, the lungs deteriorate. They become more stiff and less efficient in gas exchange.
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, the scientist said.
Knowing this, it would seem logical then to add some sighs to the breathing regimes of people on mechanical, ventilators. As it turns out, it has been tried.
On the other hand, too much sighing can add too much noise to the system and can also throw the system out of whack. This appears to be what happens to people experiencing panic attacks, said Frank Wilhelm a clinical psychologist at the University of Basel in Switzerland.
"Panic victims don't recover from sighing," said Wilhelm.
In fact, people experiencing panic attacks have been long observed to involve a great deal of sighing, and show all the symptoms of hyperventilation: dizziness, numbness in the extremities, etc., he said.