I did a series of 4 blog posts on James Nestor’s book Breath a while back:

• James Nestor on How Bad Mouth Breathing Is

• Carbon Dioxide as a Stimulant for Respiratory Function

• A Modern World of Endemic Jaw Dysfunction

• Human Skulls, Ancient and Modern

So, I was interested to see Jenny Taitz’s June 29, 2023 Wall Street Journal article “The Positive Power of a Good Sigh” on that topic. It describes “cyclic sighing”:

In a study published in January in the journal Cell Reports Medicine, Huberman and colleagues examined a technique known as “cyclic sighing.” To produce a sigh, people were instructed to close their lips and slowly inhale through the nose; then take a second inhale, completely filling the lungs; and then release an extended exhale from the mouth. Cyclic sighing involves gently repeating this sigh continuously for five minutes. The researchers found that people who practiced cyclic sighing every day for a month experienced reduced anxiety and increased positive emotions, with better results than other relaxation techniques such as mindful meditation.

Here, I think experimenting for yourself what effect it has is the best way to proceed. Here is a way Jenny Taitz suggests to think of cyclic sighing theoretically:

Intentionally heaving a physiological sigh in one way to recalibrate from breathing too much or holding our breath, as we do when we’re anxious.