| Emphysema | |
|---|---|
.jpg) | |
| Advancedcentrilobular emphysema showing totallobule involvement on the left side | |
| Specialty | Pulmonology |
| Symptoms | Shortness of breath, chronic cough[1] |
| Usual onset | Over 40 years old[1] |
| Duration | Long term[1] |
| Causes | Tobacco smoking,air pollution,genetics[1] |
| Diagnostic method | Spirometry,Lung Function Test[2] |
| Differential diagnosis | Asthma,congestive heart failure,bronchiectasis,tuberculosis,obliterative bronchiolitis,diffuse panbronchiolitis[3] |
| Prevention | Smoking cessation, improving indoor and outdoor air quality,tobacco control measures[4] |
| Treatment | Pulmonary rehabilitation,long-term oxygen therapy,lung volume reduction[4] |
| Medication | Inhaledbronchodilators andcorticosteroids[4] |
Emphysema is any air-filled enlargement in the body's tissues.[5] Most commonly emphysema refers to the permanent enlargement of air spaces (alveoli) in thelungs,[5][6] and is also known aspulmonary emphysema.
Emphysema is alower respiratory tract disease,[7] characterised by enlarged air-filled spaces in thelungs, that can vary in size and may be very large. The spaces are caused by the breakdown of thewalls of thealveoli, which replace the spongylung tissue. This reduces the total alveolar surface available forgas exchange leading to a reduction in oxygen supply for the blood.[8] Emphysema usually affects themiddle aged orolder population because it takes time to develop with the effects oftobacco smoking and other risk factors.Alpha-1 antitrypsin deficiency is a genetic risk factor that may lead to the condition presenting earlier.[9]
When associated with significant airflow limitation, emphysema is amajor subtype ofchronic obstructive pulmonary disease (COPD), a progressive lung disease characterized by long-term breathing problems and poor airflow.[10][11] Without COPD, the finding of emphysema ona CT lung scan still confers a higher mortality risk intobacco smokers.[12] In 2016 in the United States there were 6,977 deaths from emphysema – 2.2 per 100,000 people.[13] Globally it accounts for 5% of all deaths.[14] 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 andspontaneous pneumothorax.[15][16]
There are four types of emphysema, three of which are related to the anatomy of thelobules of the lung – centrilobular or centriacinar, panlobular or panacinar, and paraseptal or distal acinar emphysema – and are not associated withfibrosis (scarring).[17] The fourth type is known as paracicatricial emphysema or irregular emphysema that involves theacinus irregularly and is associated with fibrosis.[17] Though the different types can be seen onimaging they are not well-defined clinically.[18] There are also a number of associated conditions, includingbullous emphysema,focal emphysema, andRitalin 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 withsmoking.[17]
Osteoporosis is often acomorbidity of emphysema. The use ofsystemiccorticosteroids for treating exacerbations is a significant risk factor for osteoporosis, and their repeated use is recommended against.[19]
Emphysema is a respiratory disease of thelower respiratory tract.[7] It is commonly caused bytobacco smoking but some people are affected who have never smoked.[14] The presence of emphysema is a clear risk factor for lung cancer, made stronger in those who smoke.[20]
Early symptoms of emphysema vary. 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. There may be frequent cold or flu infections.[1] Other symptoms may include anxiety, depression, fatigue, sleep problems and weight loss. These symptoms could also relate to other lung conditions or other health problems;[21] therefore, emphysema is often underdiagnosed.[citation needed] The shortness of breath emphysema causes can increase over time and develop intochronic obstructive pulmonary disease.
A sign of emphysema in smokers is a higher number ofalveolar macrophages sampled from thebronchoalveolar lavage (BAL) in the lungs. The number can be four to six times greater in those who smoke than in non-smokers.[22]
Emphysema is also associated withbarrel chest.
There are four main types of emphysema, three of which are related to the anatomy of thelobules of the lung – centrilobular or centriacinar, panlobular or panacinar, and paraseptal or distal acinar and are not associated withfibrosis (scarring).[17] Although fibrosis is not a normal feature of these subtypes, repair strategies in end-stage emphysema may lead topulmonary fibrosis.[14] The fourth subtype is known as paracicatricial emphysema or irregular emphysema, involves the acinus irregularly and is associated with fibrosis.[17]
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.[17] The subtypes can be seen onimaging but are not well-defined clinically.[18]There are also a number of associated conditions including bullous emphysema, focal emphysema, and Ritalin lung.
Centrilobular emphysema, also calledcentriacinar emphysema, affects the centre of apulmonary lobule (centrilobular) in the lung, the area around the terminal bronchiole and the first respiratory bronchiole, and can be seen on imaging as an area around the tip of the visible pulmonary artery. Centrilobular emphysema is the most common type usually associated with smoking, and withchronic bronchitis.[17] The disease progresses from the centrilobular portion, leaving the lung parenchyma in the surrounding (perilobular) region preserved.[23] Usually the upper lobes of the lungs are affected.[17]
Panlobular emphysema, also calledpanacinar emphysema, affects all of the alveoli in a lobule, and can involve the whole lung or mainly the lower lobes.[18][24] This type of emphysema is associated withalpha-1 antitrypsin deficiency (A1AD or AATD), andRitalin lung,[24] and is not related to smoking.[18]
Likely complications of centrilobular and panlobular emphysema, some of which are life-threatening, include:respiratory failure,pneumonia,respiratory infections,pneumothorax,interstitial emphysema,pulmonary heart disease, andrespiratory acidosis.[25]
Paraseptal emphysema, also calleddistal acinar emphysema, relates to emphysematous change next to apleural surface, or to afissure.[18][26] The cystic spaces known asblebs or bullae that form in paraseptal emphysema typically occur in just one layer beneath the pleura. This distinguishes it from thehoneycombing of small cystic spaces seen infibrosis that typically occurs in layers.[26] This type of emphysema is not associated with airflow obstruction.[27]
When thesubpleural bullae are significant, the emphysema is calledbullous emphysema. Bullae can become extensive and combine to form giant bullae. These can be large enough to take up a third of a hemithorax, compress the lung parenchyma, and cause displacement. The emphysema is now termedgiant bullous emphysema, more commonly calledvanishing lung syndrome due to the compressed parenchyma.[28] Ableb or bulla may sometimes rupture and cause apneumothorax.[17]
Paracicatricial emphysema, also known as irregular emphysema, is seen next to areas offibrosis (scarring) as large spaces. The scarring is most often a result ofsilicosis,granulomatous infection,tuberculosis, orpulmonary infarction. It can be difficult to differentiate from thehoneycombing ofpulmonary fibrosis.[29]
Classic lung diseases are a complication ofHIV/AIDS with emphysema being a source of disease. HIV is cited as a risk factor for the development of emphysema and COPD regardless of smoking status.[30] Around 20 percent of those with HIV have increased emphysematous changes. This has suggested that an underlying mechanism related to HIV is a contributory factor in the development of emphysema. HIV associated emphysema occurs over a much shorter time than that associated with smoking; an earlier presentation is also seen in emphysema caused byalpha-1 antitrypsin deficiency. Both of these conditions predominantly show damage in the lower lungs, which suggests a similarity between the two mechanisms.[31]
Emphysema may develop in some people withalpha-1 antitrypsin deficiency, the onlygenotype of chronic obstructive pulmonary disease. This usually occurs a lot earlier (as does HIV associated emphysema) than other types.[32]
The intravenous use ofmethylphenidate, commonly marketed asRitalin and widely used as astimulant drug in the treatment ofattention deficit hyperactivity disorder, can lead to emphysematous changes known asRitalin lung. The mechanism underlying this link is not clearly understood. Ritalin tablets are not intended to be injected. They containtalc as a filler, and it has been suggested that talc exposure causesgranulomatosis leading to alveolar destruction. However, other intravenous drugs also contain talc, and no emphysematous change is associated with those.High resolution CT scanning shows the emphysema to be panlobular.[33]
Combined pulmonary fibrosis and emphysema (CPFE) is a rare syndrome that shows upper-lobe emphysema, together with lower-lobe interstitial fibrosis. This is diagnosed byCT scan.[34] This syndrome presents a marked susceptibility for the development ofpulmonary hypertension.[35]
Smoking-related interstitial fibrosis (SRIF) is another type of fibrosis that occurs in emphysematous lungs and can be identified by pathologists. 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.[36]
Congenital lobar emphysema (CLE), also known as congenital lobar overinflation and infantile lobar emphysema,[37] is aneonatal condition associated with enlarged air spaces in the lungs ofnewborn infants. It is diagnosed around the time of birth or in the first 6 months of life, occurring more often in boys than girls. CLE affects the upperlung lobes more than the lower lobes, and the left lung more often than the right lung.[38] CLE is defined as thehyperinflation of one or more lobes of the lung due to the partial obstruction of the bronchus. This causes symptoms of pressure on the nearby organs. It is associated with several cardiac abnormalities such aspatent ductus arteriosus,atrial septal defect,ventricular septal defect, andtetralogy of Fallot.[39] Although CLE may be caused by the abnormal development ofbronchi, or compression of airways by nearby tissues, no cause is identified in half of cases.[38] CT scan of the lungs is useful in assessing the anatomy of the lung lobes and status of the neighbouring lobes on whether they are hypoplastic or not. Contrast-enhanced CT is useful in assessing vascular abnormalities and mediastinal masses.[39]
Focal emphysema is a localized region of emphysema in the lung that is larger than alveoli, and often associated withcoalworker's pneumoconiosis.[40] This is also known aslocalized pulmonary emphysema.[41]Blebs and bullae may also be included as focal emphysema. These can be differentiated from the other type of enclosed air space known as alung cyst by their size and wall thickness. A bleb or bulla has a wall thickness of less than 1 mm, and are smaller.[42]
A number of occupations are associated with the development of emphysema due to the inhalation of varied gases and particles. In the USuranium mining that releasesradon gas and particles has been shown to be a cause of emphysema deaths; the figures in the study included some miners who also smoked. Uranium mining and milling was found to create environmental pollution.[43]
The inhalation ofcoal mine dust that can result incoalworker's pneumoconiosis is an independent risk factor for the development of emphysema. Focal emphysema is associated with thecoal macule, and this extends into progressive centrilobular emphysema. Less commonly a variant of panlobular emphysema develops.[44]
Silicosis results from the inhalation ofsilica particles, and the formation of large silica nodules is associated with paracicatricial emphysema, with or without bullae.[45]
Ozone is anotherpollutant that can affect the respiratory system. Long-term exposure to ozone can result in emphysema.[46]
Osteoporosis is a majorcomorbidity of emphysema. Both conditions are associated with a lowbody mass index.[47] There is an association between treating emphysema andosteoporosis; the use ofsystemiccorticosteroids for treatingexacerbations is a significant risk factor for osteoporosis, and their repeated use is not recommended.[19]
Compensatory emphysema is overinflation of part of a lung in response to either removal by surgery of another part of the lung or decreased size of another part of the lung.[48]
Pulmonary interstitial emphysema (PIE) is a collection of air inside the lungs but outside the normal air space of thealveoli, found aspneumatoses inside theconnective tissue of the peribronchovascular sheaths, interlobular septa, andvisceral pleura.
Lung volume reduction may be offered to those with advanced emphysema. When other treatments fail, and the emphysema is in the upper lobes, a surgical option may be possible.[49] A number of minimally invasivebronchoscopic procedures are increasingly used to reduce lung volume.[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.[51][52] LVRS involves the removal of tissue from the lobe most damaged by emphysema, which allows the other lobes to expand and give improved function. The procedure appears to be particularly effective if the emphysema primarily involves the upper lobes; however, the procedure increases the risk of adverse events and early death in people who have diffuse emphysema.[53][49]
Minimally invasive bronchoscopic procedures may be carried out to reduce lung volume. These include the use of valves, coils, or thermal ablation.[54][55]Endobronchial valves are one-way valves that may be used in those with severe hyperinflation resulting from advanced emphysema; a suitable target lobe and nocollateral ventilation are required for this procedure. The placement of one or more valves in the lobe induces a partialcollapse of the lobe that ensures a reduction in residual volume that improves lung function, the capacity for exercise, and quality of life.[56]
The placement of endobronchial coils made ofnitinol, instead of valves is recommended where there is collateral ventilation that would prevent the use of valves.[57][58] Nitinol is abiocompatibleshape-memory alloy.
Both of these techniques are associated with adverse effects, including persistent air leaks and cardiovascular complications. Bronchoscopic thermal vapor ablation has an improved profile. 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.[59]
Lung transplantation – the replacement of either a single lung or both (bilateral) – may be considered inend-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.[60] Careful selection as recommended by theNational Emphysema Treatment Trial (NETT) for transplant surgeries is needed as in some cases there will be an increased risk of mortality.[49] Several factors, including age and exercise tolerance using theBODE index need to be taken into account.[60] A transplant is considered only when there are no serious comorbidites.[50] ACT scan or aventilation/perfusion scan may be useful to evaluate cases for surgical interventions and to evaluate post-surgery responses.[61] Abullectomy may be carried out when a giant bulla occupies more than a third of a hemithorax.[50]
Trapped air can also develop in other tissues such as under the skin, known assubcutaneous emphysema.Orbital emphysema is the trapping of air in theorbit; a type of this ispalpebral emphysema that affects just the eyelids.[62] Emphysematousgastritis is the presence of air in the stomach wall, usually caused by a bacterial infection.[63] This is rare but has a high mortality rate.[64]
The termsemphysema andchronic bronchitis were formally defined in 1959 at theCIBA guest symposium, and in 1962 at theAmerican Thoracic Society Committee meeting on Diagnostic Standards.[65] The wordemphysema is derived fromAncient Greek ἐμφύσημα 'inflation, swelling'[66] (referring to a lung inflated by air-filled spaces), itself fromἐμφυσάωemphysao 'to blow in, to inflate',[67] composed of ἐνen, meaning "in", and φυσᾶphysa,[68] meaning "wind, blast".[69][70]
René Laennec, the physician who invented thestethoscope, used the termemphysema in his bookA Treatise on the Diseases of the Chest and of Mediate Auscultation (1837) to describe lungs that did not collapse when he opened the chest during an autopsy.[65] He noted that they did not collapse as usual because they were full of air and the airways were filled with mucus.[65] Early descriptions of probable emphysema include: in 1679 by T. Bonet of a condition of "voluminous lungs" and in 1769 byGiovanni Morgagni of lungs which were "turgid particularly from air".[65][71] In 1721 the first drawings of emphysema were made by Ruysh.[71] These were followed the illustrations ofMatthew Baillie in 1789 and descriptions of the destructive nature of the condition.
Emphysema is defined as permanent enlargement of airspaces distal to the terminal bronchiole accompanied by destruction of alveolar walls.
