Breathing parameters measured during forced exhalation are compared to normative tables based on age, sex, and height.  Such testing is termed spirometry and may be performed with use of airway bronchodilators to assess for airway bronchospasm or asthma.    
Pulmonary function assessment by Diffusion capacity measures possilbe impairment of oxygen exchange. 
All together, these results may used to evaluate lung problems such as asthma, emphysema, interstitial lung disease, pulmonary fibrosis and other disorders.