Respiratory Function Testing is a group of tests that measure how well the lungs are working. These tests assess lung capacity, airflow, and gas exchange, helping to diagnose conditions like asthma, chronic obstructive pulmonary disease (COPD), and other respiratory disorders. Common tests include spirometry, which measures the amount of air a person can inhale and exhale, and diffusion capacity tests, which evaluate how well oxygen passes from the lungs into the bloodstream. The results from these tests provide valuable information for healthcare providers to determine the severity of lung conditions and to guide treatment plans. They are typically performed in a clinical setting and may involve breathing into a device called a spirometer or using specialized equipment to measure lung function.