Tidal breathing in awake humans is variable. This variability causes changes in lung gas stores that affect gas exchange measurements. To overcome this, several algorithms provide solutions for breath-by-breath alveolar gas exchange measurement
however, there is no consensus on a physiologically robust method suitable for widespread application. A recent approach, the 'independent-breath' (IND) algorithm, avoids the complexity of measuring breath-by-breath changes in lung volume by redefining what is meant by a 'breath'. Specifically, it defines a single breathing cycle as the time between equal values of the