What does a spirometer measure?

A spirometer is a specific medical device used to measure the volume of air inhaled and exhaled by the lungs, which is essential for assessing respiratory health. By measuring various aspects of lung function, such as the amount of air taken in during a deep breath or the rate at which air is expelled, a spirometer provides critical information about lung capacities and any potential respiratory issues.

This measurement is important for diagnosing and monitoring conditions like asthma, chronic obstructive pulmonary disease (COPD), and other diseases that can affect breathing. The other options listed—heart rate, brain activity, and blood pressure—are not assessed by a spirometer, as they require different types of equipment or methodologies more suited to cardiovascular or neurological evaluations. Therefore, the correct answer is that a spirometer measures breathing volume and lung capacities.