Emphysema is a lower respiratory tract disease,[7] characterised by enlarged air-filled spaces in the lungs, that can vary in size and may be very large.

This reduces the total alveolar surface available for gas exchange leading to a reduction in oxygen supply for the blood.

[8] 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.

[10][11] Without COPD, the finding of emphysema on a CT lung scan still confers a higher mortality risk in tobacco smokers.

The use of systemic corticosteroids for treating exacerbations is a significant risk factor for osteoporosis, and their repeated use is recommended against.

[14] The presence of emphysema is a clear risk factor for lung cancer, made stronger in those who smoke.

They can include a cough (with or without sputum), wheezing, a fast breathing rate, breathlessness on exertion, and a feeling of tightness in the chest.

[citation needed] The shortness of breath emphysema causes can increase over time and develop into chronic obstructive pulmonary disease.

A sign of emphysema in smokers is a higher number of alveolar macrophages sampled from the bronchoalveolar lavage (BAL) in the lungs.

There are four main 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 and are not associated with fibrosis (scarring).

[17] The disease progresses from the centrilobular portion, leaving the lung parenchyma in the surrounding (perilobular) region preserved.

[18][24] This type of emphysema is associated with alpha-1 antitrypsin deficiency (A1AD or AATD), and Ritalin lung,[24] and is not related to smoking.

[18][26] The cystic spaces known as blebs or bullae that form in paraseptal emphysema typically occur in just one layer beneath the pleura.

[31] Emphysema may develop in some people with alpha-1 antitrypsin deficiency, the only genotype of chronic obstructive pulmonary disease.

Unlike CPFE, this type of fibrosis is usually clinically occult (i.e., does not cause symptoms or imaging abnormalities).

Occasionally, however, some patients with SRIF present with symptoms and radiologic findings of interstitial lung disease.

These can be differentiated from the other type of enclosed air space known as a lung cyst by their size and wall thickness.

[42] A number of occupations are associated with the development of emphysema due to the inhalation of varied gases and particles.

In the US uranium mining that releases radon gas and particles has been shown to be a cause of emphysema deaths; the figures in the study included some miners who also smoked.

[43] The inhalation of coal mine dust that can result in coalworker's pneumoconiosis is an independent risk factor for the development of emphysema.

[50] Where there is severe emphysema with significant hyperinflation that has proved unresponsive to other therapies, lung volume reduction surgery (LVRS) may be an option.

Both of these techniques are associated with adverse effects, including persistent air leaks and cardiovascular complications.

Heated water vapor is used to target affected lobe regions, which leads to permanent fibrosis and volume reduction.

The procedure is able to target individual lobe segments, can be carried out regardless of collateral ventilation, and can be repeated with the natural advance of emphysema.

[60] 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.

[64] The terms emphysema and chronic bronchitis were formally defined in 1959 at the CIBA guest symposium, and in 1962 at the American Thoracic Society Committee meeting on Diagnostic Standards.

[65] The word emphysema is derived from Ancient Greek ἐμφύσημα 'inflation, swelling'[66] (referring to a lung inflated by air-filled spaces), itself from ἐμφυσάω emphysao 'to blow in, to inflate',[67] composed of ἐν en, meaning "in", and φυσᾶ physa,[68] meaning "wind, blast".