Possible chronic obstructive pulmonary disease (COPD) is determined by a forced vital capacity (FVC) maneuver, measured with a hand-heal spirometer (MicroPlus Spirometer MS03, MicroMedical Ltd.). FVC is the amount of air that can be forcibly expelled from the lungs after taking the deepest breath possible. Each participant performs the FVC maneuver twice, and the average of the two trials yields the following measures:

1. Forced expiratory volume (FEV) is the average flow rate during the first second of the FVC maneuver. FEV is the average of two trials (in liters).
2. Pulmonary vital capacity (PVC) is the average of two trials to measure FVC (in liters).

Participants with a FEV/PVC ratio less than or equal to 0.7 are considered to have possible COPD, as suggested by previous literature.