Human: What is a pulmonary function test? Assistant: 
A pulmonary function test is a procedure used to measure the lung capacity and airflow of a patient. It can help diagnose respiratory diseases, such as asthma or chronic obstructive pulmonary disease (COPD), and assess the severity of the condition. The test involves measuring the amount of air that a person can inhale and exhale, as well as the speed at which they can do so.