A 72-year-old with long-standing COPD will have a reduction in which parameter on spirometry?

• A. Forced vital capacity (FVC)
• B. Total lung capacity (TLC)
• C. Residual volume (RV)
• D. RV/TLC ratio

Answer: (A)

Airflow obstruction in COPD leads to air trapping and hyperinflation, so the lungs are less able to empty fully during a forced exhalation. FVC is the total amount of air you can forcibly exhale after a full inspiration, and in COPD this emptied volume is reduced because air remains trapped in the lungs. In contrast, lung volumes themselves behave differently: total lung capacity and residual volume typically rise due to hyperinflation and air trapping, so TLC and RV are increased rather than decreased, and the ratio of RV to TLC goes up because both volumes increase but RV increases more. So, the parameter that tends to be reduced on spirometry in long-standing COPD is the forced vital capacity.