Emphysema

Emphysema is a lower respiratory tract disease,^[6] characterised by enlarged air-filled spaces in the lungs, that can vary in size and may be very large. The spaces are caused by the breakdown of the walls of the alveoli, which replace the spongy lung tissue. This reduces the total alveolar surface available for gas exchange leading to a reduction in oxygen supply for the blood.^[7] Emphysema usually affects the middle aged or older population because it takes time to develop with the effects of tobacco smoking, and other risk factors. Alpha-1 antitrypsin deficiency is a genetic risk factor that may lead to the condition presenting earlier.^[8]


When associated with significant airflow limitation, emphysema is a major subtype of chronic obstructive pulmonary disease (COPD), a progressive lung disease characterized by long-term breathing problems and poor airflow.^[9][10] Without COPD, the finding of emphysema on a CT lung scan still confers a higher mortality risk in tobacco smokers.^[11] In 2016 in the United States there were 6,977 deaths from emphysema – 2.2 per 100,000 of the population.^[12] Globally it accounts for 5% of all deaths.^[13] A 2018 review of work on the effects of tobacco and cannabis smoking found that a possibly cumulative toxic effect could be a risk factor for developing emphysema, and spontaneous pneumothorax.^[14][15]


There are four types of emphysema, three of which are related to the anatomy of the lobules of the lung – centrilobular or centriacinar, panlobular or panacinar, and paraseptal or distal acinar emphysema – and are not associated with fibrosis (scarring).^[16] The fourth type is known as paracicatricial emphysema or irregular emphysema that involves the acinus irregularly and is associated with fibrosis.^[16] Though the different types can be seen on imaging they are not well-defined clinically.^[17] There are also a number of associated conditions including bullous emphysema, focal emphysema, and Ritalin lung. Only the first two types of emphysema – centrilobular and panlobular – are associated with significant airflow obstruction, with that of centrilobular emphysema around 20 times more common than panlobular. Centrilobular emphysema is the only type associated with smoking.^[16]


Osteoporosis is often a comorbidity of emphysema. The use of systemic corticosteroids for treating exacerbations is a significant risk factor for osteoporosis, and their repeated use is recommended against.^[18]

Other surgeries[edit]

Lung transplantation – the replacement of either a single lung or both (bilateral) – may be considered in end-stage disease. A bilateral transplant is the preferred choice as complications can arise in a remaining single native lung; complications can include hyperinflation, pneumonia, and the development of lung cancer.^[59] Careful selection as recommended by the National Emphysema Treatment Trial (NETT) for transplant surgeries is needed as in some cases there will be an increased risk of mortality.^[48] Several factors including age, and poor exercise tolerance, using the BODE index need to be taken into account.^[59] A transplant is only considered where there are no serious comorbidites.^[49] A CT scan or a ventilation/perfusion scan may be useful in surgery considerations to evaluate cases for surgical interventions, and also to evaluate post-surgery responses.^[60] A bullectomy may be carried out when a giant bulla occupies more than a third of a hemithorax.^[49]

In other tissues[edit]

Trapped air can also develop in other tissues such as under the skin, known as subcutaneous emphysema. Orbital emphysema is the trapping of air in the orbit; a type of this is palpebral emphysema that affects just the eyelids.^[61] Emphysematous gastritis is the presence of air in the stomach wall, usually caused by a bacterial infection. This is a rare occurrence but has a high mortality rate.^[62]