Like all tissues, lungs respond to injury and infection through an inflammatory response. With repeated injury, the lung’s supply of alpha-1-antitrypsin is exhausted thus leaving lung tissue vulnerable to injury from its own inflammatory process – thus causing more inflammation. Years worth of chronic inflammation will result in both loss of lung tissue (especially alveolar walls) and remodelling into non-elastic tissue that can tolerate repeated inflammatory attacks. Loss of elastic properties of the lungs now makes exhalation no longer a passive process: the body must work to push the lungs into a smaller volume. This remodelling also occurs in bronchioles, resulting in narrowed airways that can’t snap open during exhalation. In some cases where emphysema is caused by inhaled irritants, there is an increased presence of cells that produce mucous (to trap the inhaled irritant), further narrowing the airway. Put together, the lungs lose the alveolar surface necessary for gas exchange and airspaces coalesce into large blebs of air trapped within the lung tissue. The narrowed airways and increase work during exhalation results in less air being exhaled, thus trapping it within the lungs. The sensation of dyspnea will increase as lung tissue is lost and remodelled and fatigue occurs both due to low oxygenation of blood and increased work in breathing (especially exhalation). Loss of lung tissue and remodelling can be visualized with CT and loss of exhalation function can be measured with pulmonary function testing (i.e. FEV1). Because the lungs can’t clear mucous and trapped pathogens/irritants as well (due to decreased exhalation abilities), emphysema patients are susceptible to lung infections. Thus, sudden changes in health status (e.g. lung infection) and/or environment (i.e. additional injury to lungs) can make emphysema symptoms worsen (exacerbation), thus requiring medical attention.
Author: Dr. Jennifer Kong (BCIT & UBC)
Gross anatomy video: Dr. Jennifer Kong (BCIT & UBC)
Histopathology video: Dr. Jonathan Bush (UBC, BC Childrens Hospital)
Author of self-tests: Noah Stewart
Nurse: Rob Kruger (Specialty Nursing, BCIT)
Medical Radiography Technologist (CT): Sarah Ho (Medical Radiography, BCIT)
Videoproducer: Ian Whittlesey (BCIT), Adrian Marcuzzi (UBC medical student) and Dr. Jennifer Kong (BCIT & UBC)