[Pulmonary function tests for diagnosis and management of asthma]

In bronchial asthma, pulmonary function tests are characterized by airway obstruction that is reversible either spontaneously or with treatment. In worsening of asthma, the parameters of FEV1, V50, V25 and RV decrease and those of sGaw and CV increase. However, compliance and diffusing capacity are within normal limits, and are very sensitive in differentiating asthma from emphysema. FEV1 is reproducible and sensitive in assessing the changes in airway caliber. Reversibility of airway obstruction is demonstrated when FEV1, is increased by more than 0.2 L or 15% of the baseline after inhalation of a beta-agonist. In severe asthma, the measurements of arterial blood gases and expiratory flow rates are essential.