The Breath-by-Breath (BbB) Method for Metabolic Measurements
The fastest responding of the non-invasive gas exchange methods for determination of metabolic rate. The principle in the determination of O2 uptake and CO2 excretion is to estimate the difference between airway influx and efflux of O2 and CO2 during inspiration and expiration.
This is done by integrating the product of O2 and CO2 concentration, respectively, and flow in the respiratory gas over an interval which covers a complete respiratory cycle.
The expiratory minute ventilation is estimated by integrating the respiratory flow over one whole expiration and dividing by the length of breath.
A number of derived parameters are provided, including respiratory exchange ratio, alveolar ventilation and anaerobic threshold.