Spirometry primarily evaluates which aspect of lung function?

• A. Pulmonary diffusion
• B. Pulmonary ventilation
• C. Pulmonary perfusion
• D. Oxygen transport in the blood

Answer: (B)

Spirometry tests how well you can move air in and out of the lungs—the ventilation aspect of lung function—by measuring air volumes and flow during forced breathing, such as FVC and FEV1. This focuses on the mechanics of the airways and lung expansion, which is why it’s the best way to assess ventilatory capacity and detect obstructive or restrictive patterns. It does not directly measure gas diffusion across the alveolar membrane (diffusion capacity tests like DLCO), pulmonary blood flow (perfusion), or how oxygen is transported in the blood, all of which involve gas exchange and circulation rather than airway mechanics.