What aspect of lung function is primarily measured during spirometry?

Spirometry is primarily designed to measure ventilation volumes, which refer to the amount of air a person can inhale and exhale from their lungs. This testing captures important parameters such as forced vital capacity (FVC) and forced expiratory volume in one second (FEV1). These measurements are critical for assessing the mechanics of breathing and diagnosing conditions like asthma, chronic obstructive pulmonary disease (COPD), and restrictive lung diseases.

In contrast to ventilation volumes, blood oxygen levels are assessed using arterial blood gases or pulse oximetry rather than spirometry. Similarly, pleural pressure, which can indicate the pressure in the pleural cavity surrounding the lungs, is not a direct measure provided by spirometry. Finally, pulmonary circulation pertains to the blood flow within the lungs, and while it affects oxygen exchange, it is not evaluated through spirometry. Thus, the primary focus of spirometry clearly aligns with measuring ventilation volumes.