A spirometer is a medical device used to measure the amount of air a person can inhale and exhale, as well as the speed of these breaths. It helps healthcare professionals assess lung function and diagnose conditions like asthma, chronic obstructive pulmonary disease (COPD), and other respiratory issues. During a spirometry test, a patient breathes into the spirometer, which records the volume and flow of air. The results provide valuable information about lung capacity and efficiency, aiding in treatment decisions and monitoring the effectiveness of therapies for respiratory diseases.