Editing Pneumothorax

{{Short description|Abnormal collection of air in the pleural space}}
{{Redirect|Collapsed lung}}
{{Good article}}
{{Use dmy dates|date=August 2018}}
{{Infobox medical condition (new)
| name            = Pneumothorax
| synonyms        = Collapsed lung<ref name=Or2004/>
| image           = Blausen 0742 Pneumothorax.png
| caption         = Illustration depicting a collapsed lung or pneumothorax
| alt             = 
| field           = [[Pulmonology]], [[thoracic surgery]]
| pronounce       = 
| symptoms        = Chest pain, [[shortness of breath]], [[fatigue (medicine)|tiredness]]<ref name=NIH2011Sym/>
| onset           = Sudden<ref name=BMJ2014/>
| duration        = 
| causes          = Unknown, trauma<ref name=BMJ2014/>
| risks           = [[COPD]], [[tuberculosis]], [[smog]], smoking<ref name=NIH2011Cau/>
| diagnosis       = [[Chest X-ray]], [[ultrasound]], [[CT scan]]<ref name=Chen2015/>
| differential    = [[Pneumatosis#Bullous emphysema|Lung bullae]],<ref name=BMJ2014/> [[hemothorax]]<ref name=NIH2011Sym/>
| prevention      = [[Smoking cessation]]<ref name=BMJ2014/>
| treatment       = [[Conservative treatment|conservative]], needle aspiration, [[chest tube]], [[pleurodesis]]<ref name=BMJ2014/>
| medication      = 
| frequency       = 20 per 100,000 per year<ref name=BMJ2014/><ref name=Chen2015/>
}}

<!-- Definition and symptoms -->
A '''pneumothorax''' is collection of air in the [[pleural space]] between the [[lung]] and the [[chest wall]].<ref name=BMJ2014/> Symptoms typically include sudden onset of sharp, one-sided [[chest pain]] and [[dyspnea|shortness of breath]].<ref name=NIH2011Sym>{{cite web|title=What Are the Signs and Symptoms of Pleurisy and Other Pleural Disorders|url=http://www.nhlbi.nih.gov/health/health-topics/topics/pleurisy/signs|website=www.nhlbi.nih.gov|access-date=31 October 2016|date=21 September 2011|url-status=live|archive-url=https://web.archive.org/web/20161008061144/https://www.nhlbi.nih.gov/health/health-topics/topics/pleurisy/signs|archive-date=8 October 2016}}</ref> In a minority of cases, a one-way valve is formed by an area of damaged [[Tissue (biology)|tissue]], and the amount of air in the space between chest wall and lungs increases; this is called a tension pneumothorax.<ref name=BMJ2014/> This can cause a steadily worsening [[Hypoxia (medical)|oxygen shortage]] and [[hypotension|low blood pressure]]. This leads to a type of shock called [[obstructive shock]], which can be fatal unless reversed.<ref name=BMJ2014/> Very rarely, both lungs may be affected by a pneumothorax.<ref>{{cite journal | vauthors = Morjaria JB, Lakshminarayana UB, Liu-Shiu-Cheong P, Kastelik JA | title = Pneumothorax: a tale of pain or spontaneity | journal = Therapeutic Advances in Chronic Disease | volume = 5 | issue = 6 | pages = 269–273 | date = November 2014 | pmid = 25364493 | pmc = 4205574 | doi = 10.1177/2040622314551549 }}</ref> It is often called a "'''collapsed lung'''", although that term may also refer to [[atelectasis]].<ref name=Or2004>{{cite book| vauthors = Orenstein DM |title=Cystic Fibrosis: A Guide for Patient and Family|date=2004|publisher=Lippincott Williams & Wilkins|isbn=9780781741521|page=62|url=https://books.google.com/books?id=BGefk9zBqlgC&pg=PA62|language=en|url-status=live|archive-url=https://web.archive.org/web/20161031212134/https://books.google.ca/books?id=BGefk9zBqlgC&pg=PA62|archive-date=31 October 2016}}</ref>

<!-- Cause and risk factors -->
A primary spontaneous pneumothorax is one that occurs without an apparent cause and in the absence of significant [[lung disease]].<ref name=BMJ2014/> A secondary spontaneous pneumothorax occurs in the presence of existing lung disease.<ref name="BMJ2014">{{cite journal | vauthors = Bintcliffe O, Maskell N | title = Spontaneous pneumothorax | journal = BMJ | volume = 348 | pages = g2928 | date = May 2014 | issue = may08 1 | pmid = 24812003 | doi = 10.1136/bmj.g2928 | s2cid = 32575512 }}</ref><ref name="Weinberger">{{cite book | vauthors = Weinberger S, Cockrill B, Mandel J |title=Principles of Pulmonary Medicine |date=2019 |publisher=Elsevier |isbn=9780323523714 |pages=215–216 |edition=7th}}</ref> Smoking increases the risk of primary spontaneous pneumothorax, while the main underlying causes for secondary pneumothorax are [[COPD]], [[asthma]], and [[tuberculosis]].<ref name=BMJ2014/><ref name=NIH2011Cau>{{cite web|title=What Causes Pleurisy and Other Pleural Disorders?|url=http://www.nhlbi.nih.gov/health/health-topics/topics/pleurisy/causes|website=NHLBI|access-date=31 October 2016|date=21 September 2011|url-status=live|archive-url=https://web.archive.org/web/20161008061131/https://www.nhlbi.nih.gov/health/health-topics/topics/pleurisy/causes|archive-date=8 October 2016}}</ref> A traumatic pneumothorax can develop from [[physical trauma]] to the [[chest]] (including a [[blast injury]]) or from a [[iatrogenesis|complication of a healthcare intervention]].<ref>{{cite journal | vauthors = Slade M | title = Management of pneumothorax and prolonged air leak | journal = Seminars in Respiratory and Critical Care Medicine | volume = 35 | issue = 6 | pages = 706–714 | date = December 2014 | pmid = 25463161 | doi = 10.1055/s-0034-1395502 | s2cid = 35518356 }}</ref><ref name="Wolf2009">{{cite journal | vauthors = Wolf SJ, Bebarta VS, Bonnett CJ, Pons PT, Cantrill SV | title = Blast injuries | journal = Lancet | volume = 374 | issue = 9687 | pages = 405–415 | date = August 2009 | pmid = 19631372 | doi = 10.1016/S0140-6736(09)60257-9 | s2cid = 13746434 }}</ref>

<!-- Diagnosis -->
Diagnosis of a pneumothorax by [[physical examination]] alone can be difficult (particularly in smaller pneumothoraces).<ref>{{cite journal | vauthors = Yarmus L, Feller-Kopman D | title = Pneumothorax in the critically ill patient | journal = Chest | volume = 141 | issue = 4 | pages = 1098–1105 | date = April 2012 | pmid = 22474153 | doi = 10.1378/chest.11-1691 | s2cid = 207386345 }}</ref> A [[chest radiograph|chest X-ray]], [[X-ray computed tomography|computed tomography]] (CT) scan, or [[ultrasound]] is usually used to confirm its presence.<ref name="Chen2015">{{cite journal | vauthors = Chen L, Zhang Z | title = Bedside ultrasonography for diagnosis of pneumothorax | journal = Quantitative Imaging in Medicine and Surgery | volume = 5 | issue = 4 | pages = 618–623 | date = August 2015 | pmid = 26435925 | pmc = 4559988 | doi = 10.3978/j.issn.2223-4292.2015.05.04 }}</ref> Other conditions that can result in similar symptoms include a [[hemothorax]] (buildup of [[blood]] in the pleural space), [[pulmonary embolism]], and [[myocardial infarction|heart attack]].<ref name=NIH2011Sym/><ref>{{cite book| vauthors = Peters JR, Egan D, Mick NW | veditors = Nadel ES |title=Blueprints Emergency Medicine|date=2006|publisher=Lippincott Williams & Wilkins|isbn=9781405104616|page=44|url=https://books.google.com/books?id=NvqaWHi1OTsC&pg=PA44|language=en|url-status=live|archive-url=https://web.archive.org/web/20161101041122/https://books.google.ca/books?id=NvqaWHi1OTsC&pg=PA44|archive-date=1 November 2016}}</ref> A large [[Chronic obstructive pulmonary disease#Pathophysiology|bulla]] may look similar on a chest X-ray.<ref name=BMJ2014/>

<!-- Treatment and epidemiology -->
A small spontaneous pneumothorax will typically resolve without treatment and requires only monitoring.<ref name=BMJ2014/> This approach may be most appropriate in people who have no underlying lung disease.<ref name=BMJ2014/> In a larger pneumothorax, or if there is shortness of breath, the air may be removed with a [[syringe]] or a [[chest tube]] connected to a one-way valve system.<ref name=BMJ2014/> Occasionally, [[surgery]] may be required if tube drainage is unsuccessful, or as a preventive measure, if there have been repeated episodes.<ref name=BMJ2014/> The surgical treatments usually involve [[pleurodesis]] (in which the layers of [[pleura]] are induced to stick together) or [[pleurectomy]] (the surgical removal of pleural membranes).<ref name=BMJ2014/> About 17–23 cases of pneumothorax occur per 100,000 people per year.<ref name=BMJ2014/><ref name=Chen2015/> They are more common in men than women.<ref name=BMJ2014/>

==Signs and symptoms==
A primary spontaneous pneumothorax (PSP) tends to occur in a young adult without underlying lung problems, and usually causes limited symptoms. Chest pain and sometimes mild breathlessness are the usual predominant presenting features.<ref name="Tschopp">{{cite journal | vauthors = Tschopp JM, Rami-Porta R, Noppen M, Astoul P | title = Management of spontaneous pneumothorax: state of the art | journal = The European Respiratory Journal | volume = 28 | issue = 3 | pages = 637–650 | date = September 2006 | pmid = 16946095 | doi = 10.1183/09031936.06.00014206 | doi-access = free }}</ref><ref name="Noppen">{{cite journal | vauthors = Noppen M, De Keukeleire T | title = Pneumothorax | journal = Respiration; International Review of Thoracic Diseases | volume = 76 | issue = 2 | pages = 121–127 | year = 2008 | pmid = 18708734 | doi = 10.1159/000135932 | doi-access = free }}</ref> In newborns [[tachypnea]], [[cyanosis]] and grunting are the most common presenting symptoms.<ref name="doi.org">{{Cite journal |last1=Andersson |first1=J. |last2=Magnuson |first2=A. |last3=Ohlin |first3=A. |date=2021-02-03 |title=Neonatal pneumothorax: symptoms, signs and timing of onset in the post-surfactant era |journal=The Journal of Maternal-Fetal & Neonatal Medicine |volume=35 |issue=25 |pages=5438–5442 |doi=10.1080/14767058.2021.1882981 |issn=1476-7058 |pmid=33535849|s2cid=231805530 |doi-access=free }}</ref> People who are affected by a PSP are often unaware of the potential danger and may wait several days before seeking medical attention.<ref name="BTS">{{cite journal | vauthors = MacDuff A, Arnold A, Harvey J | title = Management of spontaneous pneumothorax: British Thoracic Society Pleural Disease Guideline 2010 | journal = Thorax | volume = 65 | issue = 8 Suppl 2 | pages = ii18–ii31 | date = August 2010 | pmid = 20696690 | doi = 10.1136/thx.2010.136986 | title-link = British Thoracic Society | collaboration = BTS Pleural Disease Guideline Group | doi-access = free }}</ref> PSPs more commonly occur during changes in [[atmospheric pressure]], explaining to some extent why episodes of pneumothorax may happen in clusters.<ref name=Noppen/> It is rare for a PSP to cause a tension pneumothorax.<ref name=Tschopp/>

Secondary spontaneous pneumothoraces (SSPs), by definition, occur in individuals with significant underlying lung disease. Symptoms in SSPs tend to be more severe than in PSPs, as the unaffected lungs are generally unable to replace the loss of function in the affected lungs. [[Hypoxemia]] (decreased blood-oxygen levels) is usually present and may be observed as [[cyanosis]] (blue discoloration of the lips and skin). [[Hypercapnia]] (accumulation of carbon dioxide in the blood) is sometimes encountered; this may cause [[mental confusion|confusion]] and – if very severe – may result in [[coma]]s. The sudden onset of breathlessness in someone with [[chronic obstructive pulmonary disease]] (COPD), [[cystic fibrosis]], or other serious lung diseases should therefore prompt investigations to identify the possibility of a pneumothorax.<ref name=Tschopp/><ref name=BTS/>

Traumatic pneumothorax most commonly occurs when the chest wall is pierced, such as when a [[stab wound]] or [[gunshot wound]] allows air to enter the [[pleural cavity|pleural space]], or because some other mechanical injury to the lung compromises the integrity of the involved structures. Traumatic pneumothoraces have been found to occur in up to half of all cases of chest trauma, with only [[rib fracture]]s being more common in this group. The pneumothorax can be occult (not readily apparent) in half of these cases, but may enlarge – particularly if [[mechanical ventilation]] is required.<ref name=Noppen/> They are also encountered in people already receiving mechanical ventilation for some other reason.<ref name=Noppen/>

Upon [[physical examination]], [[respiratory sounds|breath sounds]] (heard with a [[stethoscope]]) may be diminished on the affected side, partly because air in the pleural space dampens the transmission of sound. Measures of the conduction of vocal vibrations to the surface of the chest may be altered. [[Percussion (medicine)|Percussion]] of the chest may be perceived as hyperresonant (like a booming drum), and [[vocal resonation|vocal resonance]] and [[fremitus|tactile fremitus]] can both be noticeably decreased. Importantly, the volume of the pneumothorax may not be well [[correlation|correlated]] with the intensity of the symptoms experienced by the victim,<ref name=BTS/> and physical signs may not be apparent if the pneumothorax is relatively small.<ref name=Noppen/><ref name=BTS/>

===Tension pneumothorax===
Tension pneumothorax is generally considered to be present when a pneumothorax (primary spontaneous, secondary spontaneous, or traumatic) leads to significant impairment of [[Respiration (physiology)|respiration]] and/or [[perfusion|blood circulation]].<ref name="Leigh-Smith">{{cite journal | vauthors = Leigh-Smith S, Harris T | title = Tension pneumothorax--time for a re-think? | journal = Emergency Medicine Journal | volume = 22 | issue = 1 | pages = 8–16 | date = January 2005 | pmid = 15611534 | pmc = 1726546 | doi = 10.1136/emj.2003.010421 }}</ref> This causes a type of circulatory shock, called [[obstructive shock]]. Tension pneumothorax tends to occur in clinical situations such as ventilation, resuscitation, trauma, or in people with lung disease.<ref name=BTS /> It is a [[medical emergency]] and may require immediate treatment without further investigations (see [[#Treatment|Treatment section]]).<ref name=BTS/><ref name=Leigh-Smith/>

The most common findings in people with tension pneumothorax are chest pain and respiratory distress, often with an increased [[heart rate]] ([[tachycardia]]) and rapid breathing ([[tachypnea]]) in the initial stages. Other findings may include quieter breath sounds on one side of the chest, low [[Oxygenation (medical)|oxygen levels]] and [[blood pressure]], and displacement of the [[human trachea|trachea]] away from the affected side. Rarely, there may be [[cyanosis]], [[altered level of consciousness]], a hyperresonant percussion note on examination of the affected side with reduced expansion and decreased movement, pain in the [[epigastrium]] (upper abdomen), displacement of the [[apex beat]] (heart impulse), and resonant sound when tapping the [[sternum]].<ref name=Leigh-Smith/>

Tension pneumothorax may also occur in someone who is receiving mechanical ventilation, in which case it may be difficult to spot as the person is typically receiving [[sedation]]; it is often noted because of a sudden deterioration in condition.<ref name=Leigh-Smith/> Recent studies have shown that the development of tension features may not always be as rapid as previously thought. Deviation of the trachea to one side and the presence of raised [[jugular venous pressure]] (distended neck veins) are not reliable as clinical signs.<ref name=Leigh-Smith/>

==Cause==
[[File:Pneumot rax bullae.JPG|thumb|upright=1.2|alt=A schematic drawing showing a bulla and a bleb, two lung abnormalities that can lead to pneumothorax |A schematic drawing of a bulla and a bleb, two lung abnormalities that may rupture and lead to pneumothorax]]

===Primary spontaneous===
Spontaneous pneumothoraces are divided into two types: ''primary'', which occurs in the absence of known lung disease, and ''secondary'', which occurs in someone with underlying lung disease.<ref name="Lyra">{{cite journal | vauthors = Lyra RD | title = Etiology of primary spontaneous pneumothorax | journal = Jornal Brasileiro de Pneumologia | volume = 42 | issue = 3 | pages = 222–226 | date = May–June 2016 | pmid = 27383937 | pmc = 5569604 | doi = 10.1590/S1806-37562015000000230 }}</ref> The cause of primary spontaneous pneumothorax is unknown, but established risk factors include being of the male sex, [[smoking]], and a [[family history (medicine)|family history]] of pneumothorax.<ref name=Rosen2010/> Smoking either [[cannabis]] or [[tobacco]] increases the risk.<ref name=BMJ2014/> The various suspected underlying mechanisms are discussed [[#Mechanism|below]].<ref name=Tschopp/><ref name=Noppen/>

===Secondary spontaneous===
Secondary spontaneous pneumothorax occurs in the setting of a variety of lung diseases. The most common is [[chronic obstructive pulmonary disease]] (COPD), which accounts for approximately 70% of cases.<ref name=Rosen2010/> The following known lung diseases may significantly increase the risk for pneumothorax.

{| class="wikitable"
! scope="col" | Type
! scope="col" | Causes
|-
! scope="row" | Diseases of the airways<ref name=Tschopp/>
| COPD (especially when [[bullous emphysema]] is present), [[asthma|acute severe asthma]], [[cystic fibrosis]]
|-
! scope="row" | Infections of the lung<ref name=Tschopp/>
| [[Pneumocystis pneumonia]] (PCP), [[tuberculosis]], [[pneumonia|necrotizing pneumonia]]
|-
! scope="row" | [[Interstitial lung disease]]<ref name=Tschopp/>
| [[Sarcoidosis]], [[idiopathic pulmonary fibrosis]], [[Langerhans cell histiocytosis|histiocytosis X]], [[lymphangioleiomyomatosis]] (LAM)
|-
! scope="row" | [[Connective tissue disease]]s<ref name=Tschopp/>
| [[Rheumatoid arthritis]], [[ankylosing spondylitis]], [[polymyositis]] and [[dermatomyositis]], [[systemic sclerosis]], [[Marfan's syndrome]] and [[Ehlers–Danlos syndrome]]
|-
! scope="row" | [[Cancer]]<ref name=Tschopp/>
| [[Lung cancer]], [[sarcoma]]s involving the lung
|-
! scope="row" | Miscellaneous<ref name=Noppen/>
| [[Catamenial pneumothorax]] (associated with the [[menstrual cycle]] and related to [[endometriosis]] in the chest)
|}

In children, additional causes include [[measles]], [[echinococcosis]], inhalation of a [[foreign body]], and certain [[congenital malformation]]s ([[congenital pulmonary airway malformation]] and [[Pneumatosis#Congenital lobar emphysema|congenital lobar emphysema]]).<ref name="Robinson">{{cite journal | vauthors = Robinson PD, Cooper P, Ranganathan SC | title = Evidence-based management of paediatric primary spontaneous pneumothorax | journal = Paediatric Respiratory Reviews | volume = 10 | issue = 3 | pages = 110–7; quiz 117 | date = September 2009 | pmid = 19651381 | doi = 10.1016/j.prrv.2008.12.003 }}</ref>

11.5% of people with a spontaneous pneumothorax have a family member who has previously experienced a pneumothorax. Several hereditary conditions – [[Marfan syndrome]], [[homocystinuria]], [[Ehlers–Danlos syndromes]], [[alpha 1-antitrypsin deficiency]] (which leads to [[Pneumatosis#Lungs|emphysema]]), and [[Birt–Hogg–Dubé syndrome]] – have all been linked to familial pneumothorax.<ref name="Chiu">{{cite journal | vauthors = Chiu HT, Garcia CK | title = Familial spontaneous pneumothorax | journal = Current Opinion in Pulmonary Medicine | volume = 12 | issue = 4 | pages = 268–272 | date = July 2006 | pmid = 16825879 | doi = 10.1097/01.mcp.0000230630.73139.f0 | s2cid = 45908721 }}</ref> Generally, these conditions cause other signs and symptoms as well, and pneumothorax is not usually the primary finding.<ref name=Chiu/> Birt–Hogg–Dubé syndrome is caused by mutations in the ''FLCN'' [[gene]] (located at [[chromosome 17]]p11.2), which encodes a protein named [[folliculin]].<ref name=Robinson/><ref name=Chiu/> ''FLCN'' mutations and lung lesions have also been identified in familial cases of pneumothorax where other features of Birt–Hogg–Dubé syndrome are absent.<ref name=Robinson/> In addition to the genetic associations, the [[human leukocyte antigen|HLA]] [[haplotype]] A<sub>2</sub>B<sub>40</sub> is also a genetic predisposition to PSP.<ref name="Fishman1520">{{Cite book |vauthors=Levine DJ, Sako EY, Peters J | title=Fishman's Pulmonary Diseases and Disorders |url=https://archive.org/details/fishmanspulmonar00afis |url-access=limited | publisher=McGraw-Hill | year=2008 | page=[https://archive.org/details/fishmanspulmonar00afis/page/n1551 1520] | edition=4th | isbn=978-0-07-145739-2 }}</ref><ref name="Light307">{{Cite book | vauthors = Light RW | title=Pleural diseases | publisher=Lippincott Williams & Wilkins | year=2007 | page=307 | edition=5th | isbn=978-0-7817-6957-0 }}</ref>

===Traumatic===
A traumatic pneumothorax may result from either [[blunt trauma]] or [[Penetrating trauma|penetrating injury]] to the chest wall.<ref name=Noppen/> The most common mechanism is the penetration of sharp bony points at a new [[rib fracture]], which damages lung tissue.<ref name=Rosen2010>{{cite book |title=Rosen's emergency medicine: concepts and clinical practice |edition=7th | vauthors = Marx J |year=2010 |publisher=Mosby/Elsevier |location=Philadelphia, PA |isbn=978-0-323-05472-0 |pages=393–96}}</ref> Traumatic pneumothorax may also be observed in those [[blast injury|exposed to blasts]], even when there is no apparent injury to the chest.<ref name=Wolf2009/>

Traumatic pneumothoraces may be classified as "open" or "closed". In an open pneumothorax, there is a passage from the external environment into the pleural space through the chest wall. When air is drawn into the pleural space through this passageway, it is known as a "sucking chest wound". A closed pneumothorax is when the chest wall remains intact.<ref name="Rathert">{{cite web|vauthors = ((Nicholas Rathert, W. Scott Gilmore, MD, EMT-P))|title=Treating Sucking Chest Wounds and Other Traumatic Chest Injuries|url=http://www.jems.com/articles/print/volume-38/issue-8/patient-care/treating-sucking-chest-wounds-and-other.html|website=www.jems.com|publisher=Journal of Emergency Medical Services|access-date=28 September 2017|archive-url=https://web.archive.org/web/20150408043836/http://www.jems.com/articles/print/volume-38/issue-8/patient-care/treating-sucking-chest-wounds-and-other.html|archive-date=8 April 2015|date=19 July 2013|url-status=dead}}</ref>

Pneumothorax was reported as an adverse event caused by misplaced [[Nasogastric intubation|nasogastric feeding tubes]]. [[Avanos Medical]]'s feeding tube placement system, the CORTRAK* 2 EAS, was recalled in May 2022 by the [[Food and Drug Administration|FDA]] due to adverse events reported, including pneumothorax, leading to 60 injuries and 23 people dying as communicated by the FDA.<ref>{{cite web |title=Avanos Medical Recalls Cortrak*2 Enteral Access System for Risk of Misplaced Enteral Tubes Could Cause Patient Harm |url=https://www.fda.gov/medical-devices/medical-device-recalls/avanos-medical-recalls-cortrak2-enteral-access-system-risk-misplaced-enteral-tubes-could-cause |archive-url=https://web.archive.org/web/20220513213417/https://www.fda.gov/medical-devices/medical-device-recalls/avanos-medical-recalls-cortrak2-enteral-access-system-risk-misplaced-enteral-tubes-could-cause |url-status=dead |archive-date=13 May 2022 |website=FDA |date=16 May 2022 |publisher=Admin |access-date=16 May 2022}}</ref>

Medical procedures, such as inserting a [[central venous catheter]] into one of the chest veins or taking [[biopsy]] samples from lung tissue, may also lead to pneumothorax. The administration of [[positive pressure ventilation]], either [[mechanical ventilation]] or [[non-invasive ventilation]], can result in [[barotrauma]] (pressure-related injury) leading to a pneumothorax.<ref name=Noppen/>

[[Underwater diving|Divers]] who breathe from an underwater apparatus are supplied with breathing gas at [[ambient pressure]], which results in their lungs containing gas at higher than atmospheric pressure. Divers breathing compressed air (such as when [[scuba diving]]) may develop a pneumothorax as a result of [[barotrauma]] from ascending just {{convert|1|m|ft|0}} while breath-holding with their lungs fully inflated.<ref name=BE2003>{{cite book |title=Bennett and Elliott's physiology and medicine of diving |edition=5th Rev |veditors=Brubakk AO, Neuman TS |year=2003 |publisher=Saunders |location=United States |isbn=978-0-7020-2571-6 | vauthors = Neuman TS |chapter=Arterial gas embolism and pulmonary barotrauma |pages=558–61}}</ref> An additional problem in these cases is that those with other features of [[decompression sickness]] are typically treated in a [[diving chamber]] with [[hyperbaric medicine|hyperbaric therapy]]; this can lead to a small pneumothorax rapidly enlarging and causing features of tension.<ref name=BE2003/>

=== Newborn infants ===
Pneumothorax is more common in neonates than in any other age group. The incidence of symptomatic neonatal is estimated to be around 1-3 per 1000 live births. Prematurity, low birth weight and asphyxia are the major risk factors, and a majority of newborn infant cases occur during the first 72 hours of life.<ref>{{Cite journal |last1=Vibede |first1=Louise |last2=Vibede |first2=Emil |last3=Bendtsen |first3=Mette |last4=Pedersen |first4=Lia |last5=Ebbesen |first5=Finn |date=2016-12-24 |title=Neonatal Pneumothorax: A Descriptive Regional Danish Study |url=http://dx.doi.org/10.1159/000453029 |journal=Neonatology |volume=111 |issue=4 |pages=303–308 |doi=10.1159/000453029 |pmid=28013308 |s2cid=4314067 |issn=1661-7800|url-access=subscription }}</ref><ref name=":0">{{cite journal | vauthors = Bruschettini M, Romantsik O, Zappettini S, O'Donnell CP, Calevo MG | title = Needle aspiration versus intercostal tube drainage for pneumothorax in the newborn | journal = The Cochrane Database of Systematic Reviews | volume = 2019 | pages = CD011724 | date = February 2019 | issue = 2 | pmid = 30707441 | pmc = 6357997 | doi = 10.1002/14651858.CD011724.pub3 }}</ref><ref name="doi.org"/>

=== Artificial Pneumothorax ===
In the late 1800s and early 1900s, physicians namely [[Carlo Forlanini]], a physician from Italy, began experimenting with intentionally collapsing the lungs of patients infected with [[tuberculosis]].<ref name=":1">{{Cite journal |last=Sakula |first=A |date=1983 |title=Carlo Forlanini, inventor of artificial pneumothorax for treatment of pulmonary tuberculosis. |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC459551/?page=5 |journal=Thorax |volume=38 |issue=5 |pages=326–332. |doi=10.1136/thx.38.5.326 |pmid=6348993 |via=PubMed|pmc=459551 }}</ref> The goal of treatment was to deprive the oxygen dependent mycobacterium of the resources it requires to multiply and spread.<ref name=":1" /> Although this method fell out of common practice following the advent of pharmaceutical advancements, some research shows that in cases where medications are not effective, AP has successful results.<ref name=":2">{{Cite journal |last=Motus |first=I. Y. |last2=Skorniakov |first2=S. N. |last3=Sokolov |first3=V. A. |last4=Egorov |first4=E. A. |last5=Kildyusheva |first5=E. I. |last6=Savel'ev |first6=A. V. |last7=Zaletaeva |first7=G. E. |date=2006-05-01 |title=Reviving an old idea: can artificial pneumothorax play a role in the modern management of tuberculosis? |url=https://www.ingentaconnect.com/content/iuatld/ijtld/2006/00000010/00000005/art00017 |journal=The International Journal of Tuberculosis and Lung Disease |volume=10 |issue=5 |pages=571–577}}</ref> However, the same complications that arise with other mechanisms may still apply, leading to questions of risk vs. benefit.<ref name=":2" />  

==Mechanism==
[[File:Pneumothorax CT.jpg|thumb|upright=1.2|alt=Image from a computed tomography (CT) scan of the chest. On the right (left side of the patient) there is a black area suggesting free air inside the chest|[[Computed tomography|CT scan]] of the chest showing a pneumothorax on the person's left side (right side on the image). A [[chest tube]] is in place (small black mark on the right side of the image), the air-filled [[pleural cavity]] (black) and [[ribs]] (white) can be seen. The [[heart]] can be seen in the center.]]

The [[thoracic cavity]] is the space inside the chest that contains the lungs, heart, and numerous major blood vessels. On each side of the cavity, a pleural membrane covers the surface of lung ([[visceral pleura]]) and also lines the inside of the chest wall ([[parietal pleura]]). Normally, the two layers are separated by a small amount of lubricating [[serous fluid]]. The lungs are fully inflated within the cavity because the pressure inside the airways ([[intrapulmonary pressure]]) is higher than the pressure inside the pleural space ([[intrapleural pressure]]). Despite the low pressure in the pleural space, air does not enter it because there are no natural connections to air-containing passages, and the pressure of gases in the bloodstream is too low for them to be forced into the pleural space.<ref name=Noppen/> Therefore, a pneumothorax can only develop if air is allowed to enter, through damage to the chest wall or to the lung itself, or occasionally because [[microorganism]]s in the pleural space produce gas.<ref name=Noppen/> Once air enters the pleural cavity, the intrapleural pressure increases, resulting in the difference between the intrapulmonary pressure and the intrapleural pressure (defined as the [[transpulmonary pressure]]) to equal zero, which cause the lungs to deflate in contrast to a normal transpulmonary pressure of ~4&nbsp;mm Hg.<ref>{{cite journal | vauthors = Neupane K, Jamil R |title=Physiology, Transpulmonary Pressure |url=https://www.ncbi.nlm.nih.gov/books/NBK559004/ |website=NCBI National Center for Biotechnology Information|year=2022 |pmid=32644430 }}</ref>

Chest-wall defects are usually evident in cases of injury to the chest wall, such as stab or bullet wounds ("open pneumothorax"). In secondary spontaneous pneumothoraces, vulnerabilities in the [[parenchyma|lung tissue]] are caused by a variety of disease processes, particularly by rupturing of [[Focal lung pneumatosis|bullae]] (large air-containing lesions) in cases of severe [[emphysema]]. Areas of [[necrosis]] (tissue death) may precipitate episodes of pneumothorax, although the exact mechanism is unclear.<ref name=Tschopp/> Primary spontaneous pneumothorax (PSP) has for many years been thought to be caused by "[[Bleb (medicine)|blebs]]" (small air-filled lesions just under the pleural surface), which were presumed to be more common in those classically at risk of pneumothorax (tall males) due to mechanical factors. In PSP, blebs can be found in 77% of cases, compared to 6% in the general population without a history of PSP.<ref name=Grundy/> As these healthy subjects do not all develop a pneumothorax later, the hypothesis may not be sufficient to explain all episodes; furthermore, pneumothorax may recur even after surgical treatment of blebs.<ref name=Noppen/> It has therefore been suggested that PSP may also be caused by areas of disruption (porosity) in the pleural layer, which are prone to rupture.<ref name=Tschopp/><ref name=Noppen/><ref name=Grundy>{{cite journal | vauthors = Grundy S, Bentley A, Tschopp JM | title = Primary spontaneous pneumothorax: a diffuse disease of the pleura | journal = Respiration; International Review of Thoracic Diseases | volume = 83 | issue = 3 | pages = 185–189 | year = 2012 | pmid = 22343477 | doi = 10.1159/000335993 | doi-access = free }}</ref> Smoking may additionally lead to [[inflammation]] and [[COPD|obstruction]] of [[bronchioles|small airways]], which account for the markedly increased risk of PSPs in smokers.<ref name=BTS/> Once air has stopped entering the pleural cavity, it is gradually reabsorbed.<ref name=BTS/>

Tension pneumothorax occurs when the opening that allows air to enter the pleural space functions as a one-way valve, allowing more air to enter with every breath but none to escape. The body compensates by increasing the [[respiratory rate]] and [[tidal volume]] (size of each breath), worsening the problem. Unless corrected, hypoxia (decreased oxygen levels) and [[respiratory arrest]] eventually follow.<ref name=Leigh-Smith/>

==Diagnosis==
The symptoms of pneumothorax can be vague and inconclusive, especially in those with a small PSP; confirmation with [[medical imaging]] is usually required.<ref name=BTS/> In contrast, tension pneumothorax is a medical emergency and may be treated before imaging – especially if there is severe hypoxia, very low blood pressure, or an impaired level of consciousness. In tension pneumothorax, X-rays are sometimes required if there is doubt about the [[anatomy|anatomical location]] of the pneumothorax.<ref name=Leigh-Smith/><ref name=Rosen2010/>

===Chest X-ray===

A plain [[chest radiograph]], ideally with the [[X-ray]] beams being projected from the back (posteroanterior, or "PA"), and during maximal inspiration (holding one's breath), is the most appropriate first investigation.<ref name="SeowKazerooni1996">{{cite journal | vauthors = Seow A, Kazerooni EA, Pernicano PG, Neary M | title = Comparison of upright inspiratory and expiratory chest radiographs for detecting pneumothoraces | journal = AJR. American Journal of Roentgenology | volume = 166 | issue = 2 | pages = 313–316 | date = February 1996 | pmid = 8553937 | doi = 10.2214/ajr.166.2.8553937 }}</ref> It is not believed that routinely taking images during expiration would confer any benefit.<ref name="MacDuffArnold2010">{{cite journal | vauthors = MacDuff A, Arnold A, Harvey J | title = Management of spontaneous pneumothorax: British Thoracic Society Pleural Disease Guideline 2010 | journal = Thorax | volume = 65 | issue = Suppl 2 | pages = ii18–ii31 | date = August 2010 | pmid = 20696690 | doi = 10.1136/thx.2010.136986 | doi-access = free }}</ref> Still, they may be useful in the detection of a pneumothorax when clinical suspicion is high but yet an inspiratory radiograph appears normal.<ref name="O'ConnorMorgan2005">{{cite journal | vauthors = O'Connor AR, Morgan WE | title = Radiological review of pneumothorax | journal = BMJ | volume = 330 | issue = 7506 | pages = 1493–1497 | date = June 2005 | pmid = 15976424 | pmc = 558461 | doi = 10.1136/bmj.330.7506.1493 }}</ref> Also, if the PA X-ray does not show a pneumothorax but there is a strong suspicion of one, lateral X-rays (with beams projecting from the side) may be performed, but this is not routine practice.<ref name=BTS/><ref name=Robinson/>

<gallery widths="180" heights="190">
File:X-ray subtle pneumothorax in inspiration - annotated.jpg|Anteroposterior inspired X-ray, showing subtle left-sided pneumothorax caused by [[port (medical)|port]] insertion
File:Lateral X-ray of pneumothorax in inspiration - annotated.jpg|Lateral inspired X-ray at the same time, more clearly showing the pneumothorax posteriorly in this case
File:Expired X-ray of pneumothorax.jpg|Anteroposterior expired X-ray at the same time, more clearly showing the pneumothorax in this case
File:Rt_sided_pneumoD.jpg|Chest X-ray showing a pneumothorax on the right (left in the image), where the absence of lung markings indicates that there is free air inside the chest
File:x-ray of pneumothorax signs.jpg|Chest X-ray showing the features of pneumothorax on the left side of the person (right in image)
</gallery>

It is not unusual for the [[mediastinum]] (the structure between the lungs that contains the heart, great blood vessels, and large airways) to be [[Mediastinal shift|shifted away]] from the affected lung due to the pressure differences. This is ''not'' equivalent to a tension pneumothorax, which is determined mainly by the constellation of symptoms, hypoxia, and [[Shock (circulatory)|shock]].<ref name=Noppen/>

The size of the pneumothorax (i.e. the volume of air in the pleural space) can be determined with a reasonable degree of accuracy by measuring the distance between the chest wall and the lung. This is relevant to treatment, as smaller pneumothoraces may be managed differently. An air rim of 2&nbsp;cm means that the pneumothorax occupies about 50% of the hemithorax.<ref name=BTS/> British professional guidelines have traditionally stated that the measurement should be performed at the level of the [[Hilum of lung|hilum]] (where blood vessels and airways enter the lung) with 2&nbsp;cm as the cutoff,<ref name=BTS/> while American guidelines state that the measurement should be done at the [[Apex of lung|apex]] (top) of the lung with 3&nbsp;cm differentiating between a "small" and a "large" pneumothorax.<ref name=Baumann>{{cite journal | vauthors = Baumann MH, Strange C, Heffner JE, Light R, Kirby TJ, Klein J, Luketich JD, Panacek EA, Sahn SA | display-authors = 6 | title = Management of spontaneous pneumothorax: an American College of Chest Physicians Delphi consensus statement | journal = Chest | volume = 119 | issue = 2 | pages = 590–602 | date = February 2001 | pmid = 11171742 | doi = 10.1378/chest.119.2.590 }}</ref> The latter method may overestimate the size of a pneumothorax if it is located mainly at the apex, which is a common occurrence.<ref name=BTS/> The various methods correlate poorly but are the best easily available ways of estimating pneumothorax size.<ref name=BTS/><ref name=Robinson/> CT scanning (see below) can provide a more accurate determination of the size of the pneumothorax, but its routine use in this setting is not recommended.<ref name=Baumann/>

Not all pneumothoraces are uniform; some only form a pocket of air in a particular place in the chest.<ref name=BTS/> Small amounts of fluid may be noted on the chest X-ray ([[hydropneumothorax]]); this may be blood ([[hemopneumothorax]]).<ref name=Noppen/> In some cases, the only significant abnormality may be the "[[deep sulcus sign]]", in which the normally small space between the chest wall and the [[Thoracic diaphragm|diaphragm]] appears enlarged due to the abnormal presence of fluid.<ref name=Leigh-Smith/>

===Computed tomography===
[[File:Pneumotórax espontâneo.png|thumb|upright=1.2|CT with the identification of underlying lung lesion: an apical bulla on the right side]]
A [[CT scan]] is not necessary for the diagnosis of pneumothorax, but it can be useful in particular situations. In some lung diseases, especially emphysema, it is possible for abnormal lung areas such as bullae (large air-filled sacs) to have the same appearance as a pneumothorax on chest X-ray, and it may not be safe to apply any treatment before the distinction is made and before the exact location and size of the pneumothorax is determined.<ref name=BTS/> In trauma, where it may not be possible to perform an upright film, chest radiography may miss up to a third of pneumothoraces, while CT remains very [[sensitivity and specificity|sensitive]].<ref name=Rosen2010/>

A further use of CT is in the identification of underlying lung lesions. In presumed primary pneumothorax, it may help to identify blebs or [[cyst|cystic lesions]] (in anticipation of treatment, see below), and in secondary pneumothorax, it can help to identify most of the causes listed above.<ref name=BTS/><ref name=Robinson/>

===Ultrasound===
[[Medical ultrasonography|Ultrasound]] is commonly used in the evaluation of people who have sustained physical trauma, for example with the [[Focused assessment with sonography for trauma|FAST protocol]].<ref name="Scalea">{{cite journal | vauthors = Scalea TM, Rodriguez A, Chiu WC, Brenneman FD, Fallon WF, Kato K, McKenney MG, Nerlich ML, Ochsner MG, Yoshii H | display-authors = 6 | title = Focused Assessment with Sonography for Trauma (FAST): results from an international consensus conference | journal = The Journal of Trauma | volume = 46 | issue = 3 | pages = 466–472 | date = March 1999 | pmid = 10088853 | doi = 10.1097/00005373-199903000-00022 | s2cid = 19871141 | doi-access = free }}</ref> Ultrasound may be more sensitive than chest X-rays in the identification of pneumothorax after [[blunt trauma]] to the chest.<ref>{{cite journal | vauthors = Wilkerson RG, Stone MB | title = Sensitivity of bedside ultrasound and supine anteroposterior chest radiographs for the identification of pneumothorax after blunt trauma | journal = Academic Emergency Medicine | volume = 17 | issue = 1 | pages = 11–17 | date = January 2010 | pmid = 20078434 | doi = 10.1111/j.1553-2712.2009.00628.x | s2cid = 8184800 | doi-access = free }}</ref> Ultrasound may also provide a rapid diagnosis in other emergency situations, and allow the quantification of the size of the pneumothorax. Several particular features on ultrasonography of the chest can be used to confirm or exclude the diagnosis.<ref name=Volpicelli>{{cite journal | vauthors = Volpicelli G | title = Sonographic diagnosis of pneumothorax | journal = Intensive Care Medicine | volume = 37 | issue = 2 | pages = 224–232 | date = February 2011 | pmid = 21103861 | doi = 10.1007/s00134-010-2079-y | s2cid = 24664490 }}</ref><ref>{{cite journal | vauthors = Staub LJ, Biscaro RR, Kaszubowski E, Maurici R | title = Chest ultrasonography for the emergency diagnosis of traumatic pneumothorax and haemothorax: A systematic review and meta-analysis | journal = Injury | volume = 49 | issue = 3 | pages = 457–466 | date = March 2018 | pmid = 29433802 | doi = 10.1016/j.injury.2018.01.033 }}</ref>

<gallery>
File:UOTW 6 - Ultrasound of the Week 1.webm|Ultrasound showing a pneumothorax<ref>{{cite web|title=UOTW #6 – Ultrasound of the Week|url=https://www.ultrasoundoftheweek.com/uotw-6/|website=Ultrasound of the Week|access-date=27 May 2017|date=24 June 2014|url-status=live|archive-url=https://web.archive.org/web/20170908222032/https://www.ultrasoundoftheweek.com/uotw-6/|archive-date=8 September 2017}}</ref>
File:UOTW 62 - Ultrasound of the Week 1.webm|Ultrasound showing a false lung point and not a pneumothorax<ref>{{cite web|title=UOTW #62 – Ultrasound of the Week|url=https://www.ultrasoundoftheweek.com/uotw-62/|website=Ultrasound of the Week|date=25 October 2015|url-status=live|archive-url=https://web.archive.org/web/20170509151907/https://www.ultrasoundoftheweek.com/uotw-62/|archive-date=9 May 2017}}</ref>
</gallery>

==Treatment==
The treatment of pneumothorax depends on a number of factors and may vary from discharge with early follow-up to immediate [[Thoracentesis|needle decompression]] or insertion of a [[chest tube]]. Treatment is determined by the severity of symptoms and indicators of [[Acute (medicine)|acute]] illness, the presence of underlying lung disease, the estimated size of the pneumothorax on X-ray, and – in some instances – on the personal preference of the person involved.<ref name=BTS/>

In traumatic pneumothorax, chest tubes are usually inserted. If mechanical ventilation is required, the risk of tension pneumothorax is greatly increased and the insertion of a chest tube is mandatory.<ref name=Noppen/><ref name=Keel>{{cite journal | vauthors = Keel M, Meier C | title = Chest injuries - what is new? | journal = Current Opinion in Critical Care | volume = 13 | issue = 6 | pages = 674–679 | date = December 2007 | pmid = 17975389 | doi = 10.1097/MCC.0b013e3282f1fe71 | s2cid = 19317500 }}</ref> Any open chest wound should be covered with an airtight seal, as it carries a high risk of leading to tension pneumothorax. Ideally, a [[Dressing (medical)|dressing]] called the "Asherman seal" should be utilized, as it appears to be more effective than a standard "three-sided" dressing. The Asherman seal is a specially designed device that adheres to the chest wall and, through a valve-like mechanism, allows air to escape but not to enter the chest.<ref name=Lee>{{cite journal | vauthors = Lee C, Revell M, Porter K, Steyn R | title = The prehospital management of chest injuries: a consensus statement. Faculty of Pre-hospital Care, Royal College of Surgeons of Edinburgh | journal = Emergency Medicine Journal | volume = 24 | issue = 3 | pages = 220–224 | date = March 2007 | pmid = 17351237 | pmc = 2660039 | doi = 10.1136/emj.2006.043687 }}</ref>

Tension pneumothorax is usually treated with urgent needle decompression. This may be required before transport to the hospital, and can be performed by an [[emergency medical technician]] or other trained professional.<ref name=Leigh-Smith/><ref name=Lee/> The needle or [[cannula]] is left in place until a chest tube can be inserted.<ref name=Leigh-Smith/><ref name=Lee/> Critical care teams are able to incise the chest to create a larger conduit as performed when placing a chest drain, but without inserting the chest tube. This is called a simple thoracostomy.<ref>{{cite journal | vauthors = Mohrsen S, McMahon N, Corfield A, McKee S | title = Complications associated with pre-hospital open thoracostomies: a rapid review | journal = Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine | volume = 29 | issue = 1 | pages = 166 | date = December 2021 | pmid = 34863280 | pmc = 8643006 | doi = 10.1186/s13049-021-00976-1 | doi-access = free }}</ref> If tension pneumothorax leads to [[cardiac arrest]], needle decompression or simple thoracostomy is performed as part of resuscitation as it may restore [[cardiac output]].<ref name=ILCOR>{{cite journal | vauthors = Neumar RW, Otto CW, Link MS, Kronick SL, Shuster M, Callaway CW, Kudenchuk PJ, Ornato JP, McNally B, Silvers SM, Passman RS, White RD, Hess EP, Tang W, Davis D, Sinz E, Morrison LJ | display-authors = 6 | title = Part 8: adult advanced cardiovascular life support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care | journal = Circulation | volume = 122 | issue = 18 Suppl 3 | pages = S729–S767 | date = November 2010 | pmid = 20956224 | doi = 10.1161/CIRCULATIONAHA.110.970988 | doi-access = free }}</ref>

===Conservative===
Small spontaneous pneumothoraces do not always require treatment, as they are unlikely to proceed to [[respiratory failure]] or tension pneumothorax, and generally resolve spontaneously. This approach is most appropriate if the estimated size of the pneumothorax is small (defined as <50% of the volume of the hemithorax), there is no [[shortness of breath|breathlessness]], and there is no underlying lung disease.<ref name=Robinson/><ref name=Baumann/> It may be appropriate to treat a larger PSP conservatively if the symptoms are limited.<ref name=BTS/> Admission to hospital is often not required, as long as clear instructions are given to return to hospital if there are worsening symptoms. Further investigations may be performed as an [[outpatient]], at which time X-rays are repeated to confirm improvement, and advice given with regard to preventing recurrence (see below).<ref name=BTS/> Estimated rates of resorption are between 1.25% and 2.2% the volume of the cavity per day. This would mean that even a complete pneumothorax would spontaneously resolve over a period of about 6&nbsp;weeks.<ref name=BTS/> There is, however, no high quality evidence comparing conservative to non conservative management.<ref>{{cite journal | vauthors = Ashby M, Haug G, Mulcahy P, Ogden KJ, Jensen O, Walters JA | title = Conservative versus interventional management for primary spontaneous pneumothorax in adults | journal = The Cochrane Database of Systematic Reviews | volume = 2018 | issue = 12 | pages = CD010565 | date = December 2014 | pmid = 25519778 | pmc = 6516953 | doi = 10.1002/14651858.CD010565.pub2 }}</ref>

Secondary pneumothoraces are only treated conservatively if the size is very small (1&nbsp;cm or less air rim) and there are limited symptoms. Admission to the hospital is usually recommended. [[Oxygen]] given at a high flow rate may accelerate resorption as much as fourfold.<ref name=BTS/><ref name="Light 310">{{Cite book | vauthors = Light RW | title=Pleural diseases | publisher=Lippincott Williams & Wilkins | year=2007 | page=310 | edition=5th | isbn=978-0-7817-6957-0 }}</ref>

===Aspiration===
In a large PSP (>50%), or in a PSP associated with breathlessness, some guidelines recommend that reducing the size by aspiration is equally effective as the insertion of a chest tube. This involves the administration of [[local anesthetic]] and inserting a needle connected to a three-way tap; up to 2.5&nbsp;liters of air (in adults) are removed. If there has been significant reduction in the size of the pneumothorax on subsequent X-ray, the remainder of the treatment can be conservative. This approach has been shown to be effective in over 50% of cases.<ref name=Tschopp/><ref name=BTS/><ref name=Robinson/> Compared to tube drainage, first-line aspiration in PSP reduces the number of people requiring hospital admission, without increasing the risk of complications.<ref>{{cite journal | vauthors = Carson-Chahhoud KV, Wakai A, van Agteren JE, Smith BJ, McCabe G, Brinn MP, O'Sullivan R | title = Simple aspiration versus intercostal tube drainage for primary spontaneous pneumothorax in adults | journal = The Cochrane Database of Systematic Reviews | volume = 9 | issue = 12 | pages = CD004479 | date = September 2017 | pmid = 28881006 | pmc = 6483783 | doi = 10.1002/14651858.CD004479.pub3 }}</ref>

Aspiration may also be considered in secondary pneumothorax of moderate size (air rim 1–2&nbsp;cm) without breathlessness, with the difference that ongoing observation in hospital is required even after a successful procedure.<ref name=BTS/> American professional guidelines state that all large pneumothoraces – even those due to PSP – should be treated with a chest tube.<ref name=Baumann/> Moderately sized [[iatrogenic]] traumatic pneumothoraces (due to medical procedures) may initially be treated with aspiration.<ref name=Noppen/>

===Chest tube===
[[File:ChesttubeforRtPneumo.png|thumb|upright=1.2|A chest tube placed on the right for a pneumothorax]]
A [[chest tube]] (or intercostal drain) is the most definitive initial treatment of a pneumothorax. These are typically inserted in an area under the [[axilla]] (armpit) called the "[[chest tube#Technique|safe triangle]]", where damage to internal organs can be avoided; this is delineated by a horizontal line at the level of the nipple and two muscles of the chest wall ([[latissimus dorsi muscle|latissimus dorsi]] and [[Pectoralis major muscle|pectoralis major]]). Local anesthetic is applied. Two types of tubes may be used. In spontaneous pneumothorax, small-bore (smaller than 14&nbsp;[[French catheter scale|F]], 4.7&nbsp;mm diameter) tubes may be inserted by the [[Seldinger technique]], and larger tubes do not have an advantage.<ref name=BTS/><ref>{{cite journal | vauthors = Chang SH, Kang YN, Chiu HY, Chiu YH | title = A Systematic Review and Meta-Analysis Comparing Pigtail Catheter and Chest Tube as the Initial Treatment for Pneumothorax | journal = Chest | volume = 153 | issue = 5 | pages = 1201–1212 | date = May 2018 | pmid = 29452099 | doi = 10.1016/j.chest.2018.01.048 | s2cid = 4587316 }}</ref> In traumatic pneumothorax, larger tubes (28&nbsp;F, 9.3&nbsp;mm) are used.<ref name=Lee/> When chest tubes are placed due to either blunt or penetrating trauma, [[antibiotic]]s decrease the risks of infectious complications.<ref>{{cite journal | vauthors = Ayoub F, Quirke M, Frith D | title = Use of prophylactic antibiotic in preventing complications for blunt and penetrating chest trauma requiring chest drain insertion: a systematic review and meta-analysis | journal = Trauma Surgery & Acute Care Open | volume = 4 | issue = 1 | pages = e000246 | date = 2019 | pmid = 30899791 | pmc = 6407548 | doi = 10.1136/tsaco-2018-000246 }}</ref>

Chest tubes are required in PSPs that have not responded to needle aspiration, in large SSPs (>50%), and in cases of tension pneumothorax. They are connected to a [[check valve|one-way valve]] system that allows air to escape, but not to re-enter, the chest. This may include a bottle with water that functions like a [[Trap (plumbing)|water seal]], or a [[Flutter valve|Heimlich valve]]. They are not normally connected to a negative pressure circuit, as this would result in rapid re-expansion of the lung and a risk of [[pulmonary edema]] ("re-expansion pulmonary edema"). The tube is left in place until no air is seen to escape from it for a period of time, and X-rays confirm re-expansion of the lung.<ref name=BTS/><ref name=Robinson/><ref name=Baumann/>

If after 2–4&nbsp;days there is still evidence of an air leak, various options are available. Negative pressure suction (at low pressures of –10 to –20&nbsp;[[Centimetre of water|cmH<sub>2</sub>O]]) at a high flow rate may be attempted, particularly in PSP; it is thought that this may accelerate the healing of the leak. Failing this, surgery may be required, especially in SSP.<ref name=BTS/>

Chest tubes are used first-line when pneumothorax occurs in people with [[AIDS]], usually due to underlying [[pneumocystis pneumonia]] (PCP), as this condition is associated with prolonged air leakage. Bilateral pneumothorax (pneumothorax on both sides) is relatively common in people with pneumocystis pneumonia, and surgery is often required.<ref name=BTS/>

It is possible for a person with a chest tube to be managed in an [[ambulatory care]] setting by using a Heimlich valve, although research to demonstrate the equivalence to hospitalization has been of limited quality.<ref name=Brims>{{cite journal | vauthors = Brims FJ, Maskell NA | title = Ambulatory treatment in the management of pneumothorax: a systematic review of the literature | journal = Thorax | volume = 68 | issue = 7 | pages = 664–669 | date = July 2013 | pmid = 23515437 | doi = 10.1136/thoraxjnl-2012-202875 | doi-access = free }}</ref>

===Pleurodesis and surgery===
[[Pleurodesis]] is a procedure that permanently eliminates the pleural space and attaches the lung to the chest wall. No long-term study (20 years or more) has been performed on its consequences. Good results in the short term are achieved with a [[thoracotomy]] (surgical opening of the chest) with identification of any source of air leakage and stapling of blebs followed by pleurectomy (stripping of the pleural lining) of the outer pleural layer and pleural abrasion (scraping of the pleura) of the inner layer. During the healing process, the lung adheres to the chest wall, effectively obliterating the pleural space. Recurrence rates are approximately 1%.<ref name=Tschopp/><ref name=BTS/> Post-thoracotomy pain is relatively common.

[[File:Bullae and Bleb.JPG|thumb|upright=1.2|[[Video-assisted thoracoscopic surgery]] (VATS) wedge resection]]

A less invasive approach is [[thoracoscopy]], usually in the form of a procedure called [[video-assisted thoracoscopic surgery]] (VATS). The results from VATS-based pleural abrasion are slightly worse than those achieved using thoracotomy in the short term, but produce smaller scars in the skin.<ref name=Tschopp/><ref name=BTS/> Compared to open thoracotomy, VATS offers a shorter in-hospital stays, less need for postoperative pain control, and a reduced risk of lung problems after surgery.<ref name=BTS/> VATS may also be used to achieve chemical pleurodesis; this involves insufflation of [[talc]], which activates an inflammatory reaction that causes the lung to adhere to the chest wall.<ref name=Tschopp/><ref name=BTS/>

If a chest tube is already in place, various agents may be instilled through the tube to achieve chemical [[pleurodesis]], such as talc, [[tetracycline]], [[minocycline]] or [[doxycycline]]. Results of chemical pleurodesis tend to be worse than when using surgical approaches,<ref name=Tschopp/><ref name=BTS/> but talc pleurodesis has been found to have few negative long-term consequences in younger people.<ref name=Tschopp/>

===Aftercare===
If pneumothorax occurs in a smoker, this is considered an opportunity to emphasize the markedly increased risk of recurrence in those who continue to smoke, and the many benefits of [[smoking cessation]].<ref name=BTS/> It may be advisable for someone to remain off work for up to a week after a spontaneous pneumothorax. If the person normally performs heavy manual labor, several weeks may be required. Those who have undergone pleurodesis may need two to three weeks off work to recover.<ref name=Brown>{{cite book |vauthors=Brown I, Palmer KT, Robin C |title=Fitness for work: the medical aspects |url=https://archive.org/details/fitnessforworkme0000palm |url-access=registration |publisher=Oxford University Press |location=Oxford |year=2007 |pages=[https://archive.org/details/fitnessforworkme0000palm/page/481 481]–82 |isbn=978-0-19-921565-2}}</ref>

[[Air travel]] is discouraged for up to seven days after complete resolution of a pneumothorax if recurrence does not occur.<ref name=BTS/> [[Underwater diving]] is considered unsafe after an episode of pneumothorax unless a preventive procedure has been performed. Professional guidelines suggest that pleurectomy be performed on both lungs and that [[spirometry|lung function tests]] and CT scan normalize before diving is resumed.<ref name=BTS/><ref name=Baumann/> Aircraft pilots may also require assessment for surgery.<ref name=BTS/>

=== Neonatal period ===
For newborn infants with pneumothorax, different management strategies have been suggested including careful observation, [[thoracentesis]] (needle aspiration), or insertion of a [[chest tube]].<ref name=":0" /> Needle aspiration may reduce the need for a chest tube, however, the effectiveness and safety of both invasive procedures have not been fully studied.<ref name=":0" />

==Prevention==
A preventative procedure ([[thoracotomy]] or thoracoscopy with pleurodesis) may be recommended after an episode of pneumothorax, with the intention to prevent recurrence. [[Evidence-based medicine|Evidence]] on the most effective treatment is still conflicting in some areas, and there is variation between treatments available in Europe and the US.<ref name=Tschopp/> Not all episodes of pneumothorax require such interventions; the decision depends largely on estimation of the risk of recurrence. These procedures are often recommended after the occurrence of a second pneumothorax.<ref name=Bau04>{{cite journal | vauthors = Baumann MH, Noppen M | title = Pneumothorax | journal = Respirology | volume = 9 | issue = 2 | pages = 157–164 | date = June 2004 | pmid = 15182264 | doi = 10.1111/j.1440-1843.2004.00577.x | s2cid = 222188018 | doi-access = free }}</ref> Surgery may need to be considered if someone has experienced pneumothorax on both sides ("bilateral"), sequential episodes that involve both sides, or if an episode was associated with pregnancy.<ref name=BTS/>

==Epidemiology==
The annual age-adjusted [[Incidence (epidemiology)|incidence rate]] (AAIR) of PSP is thought to be three to six times as high in males as in females. Fishman<ref name="Fishman1519">{{Cite book |vauthors=Levine DJ, Sako EY, Peters J | title=Fishman's Pulmonary Diseases and Disorders |url=https://archive.org/details/fishmanspulmonar00afis |url-access=limited | publisher=McGraw-Hill | year=2008 | page=[https://archive.org/details/fishmanspulmonar00afis/page/n1550 1519] | edition=4th | isbn=978-0-07-145739-2 }}</ref><ref name="Light306">{{Cite book | vauthors = Light RW | title=Pleural diseases | publisher=Lippincott Williams & Wilkins | year=2007 | page=306 | edition=5th | isbn=978-0-7817-6957-0 }}</ref> cites AAIR's of 7.4 and 1.2 cases per 100,000 person-years in males and females, respectively. Significantly above-average height is also associated with increased risk of PSP – in people who are at least 76 inches (1.93 meters) tall, the AAIR is about 200 cases per 100,000 person-years. Slim build also seems to increase the risk of PSP.<ref name="Fishman1519"/>

The risk of contracting a first spontaneous pneumothorax is elevated among male and female smokers by factors of approximately 22 and 9, respectively, compared to matched non-smokers of the same sex.<ref name="pmid3677805">{{cite journal | vauthors = Bense L, Eklund G, Wiman LG | title = Smoking and the increased risk of contracting spontaneous pneumothorax | journal = Chest | volume = 92 | issue = 6 | pages = 1009–1012 | date = December 1987 | pmid = 3677805 | doi = 10.1378/chest.92.6.1009 | s2cid = 16838594 }}</ref> Individuals who smoke at higher intensity are at higher risk, with a "greater-than-linear" effect; men who smoke 10 cigarettes per day have an approximate 20-fold increased risk over comparable non-smokers, while smokers consuming 20 cigarettes per day show an estimated 100-fold increase in risk.<ref name="Fishman1519"/>

In secondary spontaneous pneumothorax, the estimated annual AAIR is 6.3 and 2.0 cases per 100,000 person-years for males and females,<ref name="Fishman1520"/><ref name="Light315">{{Cite book | vauthors = Light RW | title=Pleural diseases | publisher=Lippincott Williams & Wilkins | year=2007 | page=315 | edition=5th | isbn=978-0-7817-6957-0 }}</ref> respectively, with the risk of recurrence depending on the presence and severity of any underlying lung disease. Once a second episode has occurred, there is a high likelihood of subsequent further episodes.<ref name=Tschopp/> The incidence in children has not been well studied,<ref name=Robinson/> but is estimated to be between 5 and 10 cases per 100,000 person-years.<ref name=Sahn2000>{{cite journal | vauthors = Sahn SA, Heffner JE | title = Spontaneous pneumothorax | journal = The New England Journal of Medicine | volume = 342 | issue = 12 | pages = 868–874 | date = March 2000 | pmid = 10727592 | doi = 10.1056/NEJM200003233421207 }}</ref>

Death from pneumothorax is very uncommon (except in tension pneumothoraces). British statistics show an annual mortality rate of 1.26 and 0.62 deaths per million person-years in men and women, respectively.<ref name=BTS/> A significantly increased risk of death is seen in older people and in those with secondary pneumothoraces, when the lung collapses due to another underlying health condition such as [[Chronic obstructive pulmonary disease|chronic lung disease]].<ref name=Tschopp/>

==History==
An early description of traumatic pneumothorax secondary to rib fractures appears in ''Imperial Surgery'' by Turkish surgeon [[Şerafeddin Sabuncuoğlu]] (1385–1468), which also recommends a method of simple aspiration.<ref name=Anatolia>{{cite journal | vauthors = Kaya SO, Karatepe M, Tok T, Onem G, Dursunoglu N, Goksin I | title = Were pneumothorax and its management known in 15th-century anatolia? | journal = Texas Heart Institute Journal | volume = 36 | issue = 2 | pages = 152–153 | date = September 2009 | pmid = 19436812 | pmc = 2676596 }}</ref>

Pneumothorax was described in 1803 by [[Jean Marc Gaspard Itard]], a student of [[René Laennec]], who provided an extensive description of the clinical picture in 1819.<ref>{{cite book | vauthors = Laennec RT | title=Traité de l'auscultation médiate et des maladies des poumons et du coeur – part II | language=fr | location=Paris | year=1819}}</ref> While Itard and Laennec recognized that some cases were not due to [[tuberculosis]] (then the most common cause), the concept of spontaneous pneumothorax in the absence of tuberculosis (primary pneumothorax) was reintroduced by the Danish physician Hans Kjærgaard in 1932.<ref name=BTS/><ref name=Grundy/><ref>{{cite journal | vauthors=Kjærgard H | title=Spontaneous pneumothorax in the apparently healthy | journal=Acta Medica Scandinavica | year=1932 | volume=43 | issue = Suppl | pages=1–159 | doi=10.1111/j.0954-6820.1932.tb05982.x}}</ref> In 1941, the surgeons Tyson and Crandall introduced pleural abrasion for the treatment of pneumothorax.<ref name=BTS/><ref>{{cite journal |vauthors=Tyson MD, Crandall WB | title=The surgical treatment of recurrent idiopathic spontaneous pneumothorax | journal=Journal of Thoracic Surgery | year=1941 | volume=10 | issue=5 | pages=566–70| doi=10.1016/S0096-5588(20)32206-6 | doi-access= }}</ref>

Prior to the advent of [[Tuberculosis treatment|anti-tuberculous medications]], pneumothoraces were intentionally caused by healthcare providers in people with tuberculosis in an effort to collapse a [[Lung#Anatomy|lobe]], or entire [[lung]], around a cavitating [[lesion]]. This was known as "resting the lung". It was introduced by the Italian surgeon [[Carlo Forlanini]] in 1888 and publicized by the American surgeon [[John Benjamin Murphy]] in the early 20th century (after discovering the same procedure independently). Murphy used the (then) recently discovered X-ray technology to create pneumothoraces of the correct size.<ref>{{cite journal | vauthors = Herzog H | title = History of tuberculosis | journal = Respiration; International Review of Thoracic Diseases | volume = 65 | issue = 1 | pages = 5–15 | year = 1998 | pmid = 9523361 | doi = 10.1159/000029220 | s2cid = 202645306 }}</ref>

==Etymology==

The word ''pneumothorax'' comes from Greek ''[[wikt:pneumo-|pneumo-]]'' 'air' and ''[[chest|thorax]]'' 'chest'.<ref>{{cite book| vauthors = Stevenson A |title=Oxford Dictionary of English|date=2010|publisher=OUP Oxford |isbn=9780199571123 |page=1369|url=https://books.google.com/books?id=anecAQAAQBAJ&pg=PA1369|language=en|url-status=live|archive-url=https://web.archive.org/web/20160914232800/https://books.google.ca/books?id=anecAQAAQBAJ&pg=PA1369|archive-date=14 September 2016}}</ref> Its plural is ''pneumothoraces''.

==Other animals==
Non-human animals may experience both spontaneous and traumatic pneumothorax. Spontaneous pneumothorax is, as in humans, classified as primary or secondary, while traumatic pneumothorax is divided into open and closed (with or without chest wall damage).<ref name=Pawloski>{{cite journal | vauthors = Pawloski DR, Broaddus KD | title = Pneumothorax: a review | journal = Journal of the American Animal Hospital Association | volume = 46 | issue = 6 | pages = 385–397 | year = 2010 | pmid = 21041331 | doi = 10.5326/0460385 }}</ref> The diagnosis may be apparent to the [[veterinary physician]] because the animal exhibits difficulty breathing in, or has shallow breathing. Pneumothoraces may arise from lung lesions (such as bullae) or from trauma to the chest wall.<ref name=Merck1>{{cite news | title=Causes of Respiratory Malfunction | work=Merck Veterinary Manual, 9th edition (online version) | url=http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/toc_91000.htm | year=2005 | access-date=5 June 2011 | url-status=live | archive-url=https://web.archive.org/web/20101126122530/http://merckvetmanual.com/mvm/index.jsp?cfile=htm%2Fbc%2Ftoc_91000.htm | archive-date=26 November 2010 }}</ref> In horses, traumatic pneumothorax may involve both hemithoraces, as the [[mediastinum]] is incomplete and there is a direct connection between the two halves of the chest.<ref name=Merck2>{{cite web | title=Equine trauma and first aid: wounds and lacerations | work=Merck Veterinary Manual, 9th edition (online version) | url=http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/160810.htm | year=2005 | access-date=5 June 2011 | url-status=live | archive-url=https://web.archive.org/web/20090906123324/http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm%2Fbc%2F160810.htm | archive-date=6 September 2009 }}</ref> Tension pneumothorax – the presence of which may be suspected due to rapidly deteriorating heart function, absent lung sounds throughout the thorax, and a barrel-shaped chest – is treated with an incision in the animal's chest to relieve the pressure, followed by insertion of a chest tube.<ref name=Merck3>{{cite web | title=Primary survey and triage - breathing | work=Merck Veterinary Manual, 9th edition (online version) | url=http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/160203.htm | year=2005 | access-date=5 June 2011 | url-status=live | archive-url=https://web.archive.org/web/20111028144738/http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm%2Fbc%2F160203.htm | archive-date=28 October 2011 }}</ref> For spontaneous pneumothorax the use of CT for diagnosis has been described for dogs<ref>{{cite journal | vauthors = Au JJ, Weisman DL, Stefanacci JD, Palmisano MP | title = Use of computed tomography for evaluation of lung lesions associated with spontaneous pneumothorax in dogs: 12 cases (1999-2002) | journal = Journal of the American Veterinary Medical Association | volume = 228 | issue = 5 | pages = 733–737 | date = March 2006 | pmid = 16506938 | doi = 10.2460/javma.228.5.733 | doi-access = free }}</ref> and Kunekune pigs.<ref>{{cite journal | vauthors = Smith J, Cuneo M, Walton R, White R, Busch R, Chigerwe M |title=Spontaneous Pneumothorax in a Companion Kunekune Pig due to Pulmonary Bullae Rupture |journal=Journal of Exotic Pet Medicine |date=April 2020 |volume=34 |pages=6–9 |doi=10.1053/j.jepm.2020.04.001|s2cid=218806957 |url=https://lib.dr.iastate.edu/vdpam_pubs/189 }}</ref>

== References ==
{{Reflist}}

{{Medical condition classification and resources
|  ICD10          = {{ICD10|J|93||j|90}}, {{ICD10|P|25|1|p|20}}, {{ICD10|S|27|0|s|20}} 
|  ICD9           = {{ICD9|512}}, {{ICD9|860}} 
|  eMedicineSubj  = article 
|  eMedicineTopic = 432979
|  eMedicine_mult = {{eMedicine2|article|424547}} {{eMedicine2|article|360796}} {{eMedicine2|article|808162}} {{eMedicine2|article|827551}} {{eMedicine2|article|1003552}} 
|  OMIM           = 173600 
|  DiseasesDB     = 10195
|  MedlinePlus    = 000087 
|  MeshID         = D011030 
}}
{{Respiratory pathology}}
{{Trauma |state=autocollapse}}
{{Chest trauma}}
{{Authority control}}

[[Category:Chest trauma]]
[[Category:Disorders of fascia]]
[[Category:Medical emergencies]]
[[Category:Wikipedia emergency medicine articles ready to translate]]
[[Category:Wikipedia medicine articles ready to translate]]