What is double inhale exhale?

The double inhale-exhale, also known as the physiological sigh, is a breathing technique discussed by Andrew Huberman. This technique involves taking two quick inhales followed by one long exhale. The purpose of the double inhale is to maximally fill the lungs, which helps reinflate the alveoli (the tiny sacs within the lungs). When these sacs are fully inflated, they can offload more carbon dioxide from the bloodstream during the exhale. This process helps reduce stress and increase calmness rapidly by optimizing the oxygen and carbon dioxide balance in the blood 1 2 3.