What is the purpose and interpretations of the pulmonary function test? Pulmonary function tests will test the mechanical function of the lungs, chest wall, and respiratory muscles by measuring the total volume of air exhaled from a full lung (total lung capacity [TLC]) to maximal expiration (residual volume [RV]). This volume, the forced vital capacity (FVC) and the forced expiratory volume in the first second of the forceful exhalation (FEV1), In Emphysema, spirometry may show typical obstructive pattern due to the blockage of the air during expiration. As a result of the air trapping, the spirometry will show decreased in FVC, but less than the FEV 1, and increased FRC and RV.(McCance, &Huether, 2013).