Overview of chronic obstructive pulmonary disease (COPD)

COPD is a respiratory disorder characterized by chronic air flow obstruction, which encompasses both emphysema and chronic bronchitis, which share similar etiologic factors, and often occur together. COPD is currently the sixth leading cause of death worldwide, and the fourth leading cause of death in the United States, where it affects over 16 million people.

The most significant environmental risk factor for the development of COPD is cigarette smoking. Chronic exposure to cigarette smoke is thought to trigger an inflammatory response within the airways, recruiting immune cells to the alveoli. Immune cells release proteases, which damage the elastic components of the lung’s extracellular matrix (ECM), causing cell death, sagging and expansion of individual alveoli into the larger contagious air spaces. Loss of alveolar surface area reduces alveolar gas exchange, while loss of elasticity reduces the elastic recoil that assists expiration. Both factors contributing to the sensations of breathlessness typical of this condition.

Smoking has also been linked to increase in the size and number of mucus secreting goblet cells in the large and small airways, as well as the disruption of mucociliary clearance. These cellular changes lead to excessive mucus production, which narrows the airways and must be cleared by cough, fulfilling the clinical definition of chronic bronchitis. The initial manifestations of COPD are cough, sputum production, and shortness of breath during exercise, especially when involving the arms.

Review Date:4/10/2025
Reviewed By:Allen J. Blaivas, DO, Division of Pulmonary, Critical Care, and Sleep Medicine, VA New Jersey Health Care System, Clinical Assistant Professor, Rutgers New Jersey Medical School, East Orange, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997-A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

The Agency for Health Care Administration (Agency) and this website do not claim the information on, or referred to by, this site is error free. This site may include links to websites of other government agencies or private groups. Our Agency and this website do not control such sites and are not responsible for their content. Reference to or links to any other group, product, service, or information does not mean our Agency or this website approves of that group, product, service, or information.

Additionally, while health information provided through this website may be a valuable resource for the public, it is not designed to offer medical advice. Talk with your doctor about medical care questions you may have.