Respiratory Function Tests, also known as pulmonary function tests, are a group of non-invasive procedures that measure how well the lungs are working. These tests assess various aspects of lung function, including airflow, lung volume, and gas exchange. Common tests include spirometry, which measures the amount and speed of air inhaled and exhaled, and diffusion capacity tests, which evaluate how well oxygen passes from the lungs into the bloodstream. These tests are essential for diagnosing and monitoring respiratory conditions such as asthma, chronic obstructive pulmonary disease (COPD), and pulmonary fibrosis. They help healthcare providers determine the severity of lung disease and guide treatment decisions.