Which statement best defines spirometry?

• A. A noninvasive test that measures the exhalation capacity of the lungs.
• B. An imaging test to visualize the lungs.
• C. A test that assesses diffusion capacity using carbon monoxide.
• D. A test that measures oxygen saturation by pulse oximetry.

Answer: (A)

Spirometry is a pulmonary function test that measures how much air you can exhale and how quickly, after a deep breath. It uses a mouthpiece and records airflow to compute values like forced vital capacity (FVC) and the rate of exhalation in the first second (FEV1), along with their ratio. This focuses on airflow and exhalation capacity, not on imaging the lungs, measuring diffusion, or oximetry. That’s why the best definition is a noninvasive test that measures the exhalation capacity of the lungs. The other options describe different tests: imaging studies visualize the lungs; diffusion capacity testing uses carbon monoxide (DLCO); and pulse oximetry measures oxygen saturation.