Chronic obstructive pulmonary disease (COPD) is a lung condition caused by chronic inflammation in your airways and lungs. This inflammation can cause swelling and tissue damage that block the flow of air into your lungs, making it difficult to breathe.  

COPD is a persistent and often progressive condition, meaning the symptoms can get worse over time. To help quantify the severity and progression of symptoms, COPD is divided into four grades based on how much it affects your breathing and how often you experience exacerbations or flare-ups. These criteria were developed by a group known as the Global Initiative for Chronic Obstructive Lung Disease (GOLD) and are commonly referred to as GOLD grades or stages.

Healthcare professionals may use a series of questionnaires to assess symptoms and risk for COPD exacerbations. A lung function test called spirometry measures the amount of air a person can force out of their lungs in 1 second. This value is known as the forced expiratory volume, or FEV1.

Click through the infographic below to learn more about the different grades of COPD and how symptoms can change as COPD progresses.