Evaluation of a method of estimating the basal metabolic rate.

While the patient is breathing normally into the spirometer he is instructed to make a deep expiration. It is important to ensure the maximal possible emptying of the lung so that all the reserve (supplemental) air will be expelled into the spirometer. To achieve this the subject must be stimulated to go on expelling air until the expiratory line flattens out. This process is repeated once or twice at two to six minute intervals. The oxygen line is traced by joining the points of extreme expiration.