Stage 2 COPD is characterized by a pulmonary function test that is 50 to 80 percent of the expected response, according to Healthline. Additionally, people with stage 2 COPD may have moderate-to-severe shortness of breath when exerting themselves, and they may have a cough or sputum.
Sputum is the mucus that is coughed up from the lungs of a person with COPD, as stated by Healthline. COPD stands for chronic obstructive pulmonary disease, a disease that has four stages. Stage 1 COPD includes some shortness of breath and PFT results of 80 percent or more of the predicted response. At stage 3, people with COPD experience more severe shortness of breath, and exercise is very difficult. Stage 4 sufferers may experience episodes of shortness of breath that are life-threatening.
Pulmonary function tests determine how well the lungs are working, reports WebMD. PFTs measure how much air the lungs can hold, how fast air moves in and out of the lungs, and how efficiently the lungs place oxygen into and remove carbon dioxide from the blood. Other types of tests, including gas diffusion tests, body plethysmography, inhalation challenge tests, stress tests and residual volume, are also performed to determine lung function.