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{{Pneumothorax}}
{{Pneumothorax}}
{{CMG}}
{{CMG}}; {{AE}} {{FT}}, {{HQ}}


==Overview==
==Overview==
Pneumothorax is air in the pleural space under pressure resulting in [[lung]] collapse.The pathophysiology of each type depends on the underlying disease/etiology. Primary spontaneous pneumothorax most commonly results from the [[bleb]] (small air-filled lesions under [[Pleural cavity|pleural]] surface) rupture allowing the air to leak into the [[Pleural cavity|pleural]] space. A subclass of primary spontaneous pneumothorax is isolated familial primary spontaneous pneumothorax which is [[Genetics|genetically]] associated with [[folliculin]] [[gene]] [[mutation]]. Secondary spontaneous pneumothorax occurs subsequent to underlying [[lung]] pathology such as [[Chronic obstructive pulmonary disease|obstructive lung disease]], [[cystic fibrosis]], [[Interstitial lung disease|diffuse parenchymal lung disease]] and [[lung cancer]]. In tension pneumothorax, the underlying pathophysiology most commonly is [[chest]] [[Physical trauma|trauma]] forming a one-way valve in the pleura whereby air enters the pleural space when the pleural pressure is negative during inspiration. Pneumothorax can also result from several interventional procedures which cause penetrating or non-penetrating injury to the pleura resutling in abrupt increase in the alveolar pressure and hence, lead to alveolar rupture forming a communication with the pleura.


==Pathophysiology==
==Pathophysiology==
The [[lungs]] are located inside the chest cavity, which is a hollow spaceAir is drawn into the lungs by the [[diaphragm (anatomy)|diaphragm]] (a powerful [[abdomen|abdominal]] [[muscle]]). The [[pleural cavity]] is the region between the chest wall and the lungs. If air enters the pleural cavity, either from the outside (open pneumothorax) or from the lung (closed pneumothorax), the lung collapses and it becomes mechanically impossible for the injured person to breathe, even with an open [[airway]].  If a piece of tissue forms a one-way valve that allows air to enter the pleural cavity from the lung but not to escape, overpressure can build up with every breath; this is known as [[tension pneumothorax]]. It may lead to severe shortness of breath as well as circulatory collapse, both life-threatening conditions. This condition requires urgent intervention.
===Anatomy and physiology of the thoracic cavity===
The normal [[anatomy]] and [[physiology]] of [[thoracic cavity]] is as follows:
*[[Chest|Thoracic]] cavity is defined as the space inside the [[chest]] that contains the [[heart]], [[Lung|lungs]], and, several major [[blood]] [[Blood vessel|vessels]].<ref name="pmidhttps://www.ncbi.nlm.nih.gov/pubmed/22343477">{{cite journal| author=Grundy S, Bentley A, Tschopp JM| title=Primary spontaneous pneumothorax: a diffuse disease of the pleura. | journal=Respiration | year= 2012 | volume= 83 | issue= 3 | pages= 185-9 | pmid=https://www.ncbi.nlm.nih.gov/pubmed/22343477 | doi=10.1159/000335993 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22343477  }} </ref><ref name="pmid18197926">{{cite journal| author=Lee SC, Cheng YL, Huang CW, Tzao C, Hsu HH, Chang H| title=Simultaneous bilateral primary spontaneous pneumothorax. | journal=Respirology | year= 2008 | volume= 13 | issue= 1 | pages= 145-8 | pmid=18197926 | doi=10.1111/j.1440-1843.2007.01168.x | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=18197926 }} </ref><ref name="BintcliffeMaskell2014">{{cite journal|last1=Bintcliffe|first1=O.|last2=Maskell|first2=N.|title=Spontaneous pneumothorax|journal=BMJ|volume=348|issue=may08 1|year=2014|pages=g2928–g2928|issn=1756-1833|doi=10.1136/bmj.g2928}}</ref>
 
*On either side of the [[cavity]], a [[Pleural cavity|pleural]] membrane covers the outside surface of the [[lung]] (visceral [[Pleural cavity|pleura]]) and also lines the inside of the [[Thoracic cavity|chest wall]] ([[parietal]] [[Pleural cavity|pleura]]).
*The two layers are separated by a small amount of lubricating serous fluid known as the [[Pleural cavity|pleural]] fluid.
*The [[Lung|lungs]] are fully inflated within the [[cavity]] as the pressure inside the [[Airway|airways]] is higher than the pressure inside the [[Pleural cavity|pleural]] space.
*The inhaled air does not enter the [[Pleural cavity|pleural]] space as there is no natural connections between them as well as the pressure of gases in the [[blood]] stream is too low for them to be forced into the [[Pleural cavity|pleural]] space.
*The [[Pleural cavity|pleural]] pressure is negative with respect to atmospheric pressure during spontaneous [[breathing]].
*Air can enter the [[pleural]] space through the following mechanisms:<ref name="pmid16946095">{{cite journal| author=Tschopp JM, Rami-Porta R, Noppen M, Astoul P| title=Management of spontaneous pneumothorax: state of the art. | journal=Eur Respir J | year= 2006 | volume= 28 | issue= 3 | pages= 637-50 | pmid=16946095 | doi=10.1183/09031936.06.00014206 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16946095  }} </ref><ref name="GrundyBentley2012">{{cite journal|last1=Grundy|first1=Seamus|last2=Bentley|first2=Andrew|last3=Tschopp|first3=Jean-Marie|title=Primary Spontaneous Pneumothorax: A Diffuse Disease of the Pleura|journal=Respiration|volume=83|issue=3|year=2012|pages=185–189|issn=1423-0356|doi=10.1159/000335993}}</ref><ref name="pmid9144053">{{cite journal| author=Barton ED, Rhee P, Hutton KC, Rosen P| title=The pathophysiology of tension pneumothorax in ventilated swine. | journal=J Emerg Med | year= 1997 | volume= 15 | issue= 2 | pages= 147-53 | pmid=9144053 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9144053  }} </ref>
**Damage to the [[Pleural cavity|pleura]] or the [[chest]] wall
** Damage to the [[Lung|lungs]]
** Microorganisms in the [[Pleural cavity|pleural]] space
 
[[File:Pleurisy and pneumothorax.jpg|thumb|left|369x369px|Pneumothorax [https://commons.wikimedia.org/wiki/File%3APleurisy_and_pneumothorax.jpg Source:By National Heart Lung and Blood Institute, via Wikimedia Commons]]]
<br clear="left" />
 
===Pathogenesis===
The [[pathophysiology]] of pneumothorax depends on the underlying disease causing it.
 
===Primary spontaneous pneumothorax===
*The most common underlying pathology of primary spontaneous pneumothorax is an apical subpleural [[bleb]] (small air-filled lesions under the [[Pleural cavity|pleural]] surface).<ref name="pmid21038147">{{cite journal| author=Yazkan R, Han S| title=Pathophysiology, clinical evaluation and treatment options of spontaneous pneumothorax. | journal=Tuberk Toraks | year= 2010 | volume= 58 | issue= 3 | pages= 334-43 | pmid=21038147 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21038147  }} </ref>
* In addition, [[smoking]] causes [[inflammation]] and [[obstruction]] of the small airways, which is responsible for the increased risk of primary spontaneous pneumothorax in smokers.
 
===Secondary spontaneous pneumothorax===
* Pneumothorax due to underlying [[lung]] disease is secondary spontaneous pneumothorax.
 
===Tension pneumothorax===
*Tension pneumothorax develops when a [[Disruption (of schema)|disruption]] involves the [[visceral pleura]], [[parietal pleura]], or the [[Tracheobronchial tree|tracheobronchial]] tree.<ref name="pmid23764307">{{cite journal| author=Nelson D, Porta C, Satterly S, Blair K, Johnson E, Inaba K et al.| title=Physiology and cardiovascular effect of severe tension pneumothorax in a porcine model. | journal=J Surg Res | year= 2013 | volume= 184 | issue= 1 | pages= 450-7 | pmid=23764307 | doi=10.1016/j.jss.2013.05.057 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23764307  }} </ref><ref name="pmid7662057">{{cite journal| author=Plewa MC, Ledrick D, Sferra JJ| title=Delayed tension pneumothorax complicating central venous catheterization and positive pressure ventilation. | journal=Am J Emerg Med | year= 1995 | volume= 13 | issue= 5 | pages= 532-5 | pmid=7662057 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=7662057  }} </ref>
 
*The disruption occurs when a one-way valve forms, allowing air inflow into the [[Pleural cavity|pleural]] space, and prohibiting air outflow.
*The volume of this nonabsorbable intrapleural air increases with each inspiration.
*As a result, pressure rises within the affected hemithorax; ipsilateral [[lung]] collapses and causes [[Hypoxemia|hypoxia]].
*Further pressure causes the [[mediastinum]] shift toward the contralateral side and compresses both, the contralateral [[lung]] and the vasculature entering the right [[Atrium (heart)|atrium]] of the heart.
* This leads to worsening [[Hypoxemia|hypoxia]] and compromised [[Vein|venous]] return.
 
===Iatrogenic pneumothorax===
Following procedures commonly cause [[Iatrogenesis|iatrogenic]] pneumothorax:<ref name="pmid26557487">{{cite journal| author=Kornbau C, Lee KC, Hughes GD, Firstenberg MS| title=Central line complications. | journal=Int J Crit Illn Inj Sci | year= 2015 | volume= 5 | issue= 3 | pages= 170-8 | pmid=26557487 | doi=10.4103/2229-5151.164940 | pmc=4613416 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=26557487  }} </ref><ref name="pmid15077937">{{cite journal| author=Peuker E| title=Case report of tension pneumothorax related to acupuncture. | journal=Acupunct Med | year= 2004 | volume= 22 | issue= 1 | pages= 40-3 | pmid=15077937 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=15077937  }} </ref>
*Central [[Cannula|cannulation]]<ref name="pmid27437303">{{cite journal| author=Kumar M, Singh A, Sidhu KS, Kaur A| title=Malposition of Subclavian Venous Catheter Leading to Chest Complications. | journal=J Clin Diagn Res | year= 2016 | volume= 10 | issue= 5 | pages= PD16-8 | pmid=27437303 | doi=10.7860/JCDR/2016/19399.7860 | pmc=4948479 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=27437303  }} </ref>
*[[Transthoracic needle aspiration|Transthoracic]] needle aspiration
*[[Thoracentesis|Thoracocentesis]]
* Mechanical [[Ventilation (physiology)|ventilation]]
*[[Chest|Thoracic]] acupuncture<ref name="pmid18818566">{{cite journal| author=Juss JK, Speed CA, Warrington J, Mahadeva R| title=Acupuncture induced pneumothorax - a case report. | journal=Acupunct Med | year= 2008 | volume= 26 | issue= 3 | pages= 193-6 | pmid=18818566 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=18818566 }} </ref><ref name="pmid11845568">{{cite journal| author=Ramnarain D, Braams R| title=[Bilateral pneumothorax in a young woman after acupuncture]. | journal=Ned Tijdschr Geneeskd | year= 2002 | volume= 146 | issue= 4 | pages= 172-5 | pmid=11845568 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=11845568  }} </ref>
*Transbronchial [[lung]] [[biopsy]] or transpleural intervention
*[[Intravenous therapy|Intravenous]] drug abusers using neck veins
*Aggressive [[cardiopulmonary resuscitation]]
'''Mechanism of injury:'''
*[[Iatrogenesis|Iatrogenic]] pneumothorax causes penetrating or non-penetrating injury to the pleura resulting in abrupt increase in the [[Alveolus|alveolar]] pressure, which can lead to [[Alveolus|alveolar]] rupture.
*Once the [[alveolus]] is ruptured, air enters the [[interstitial]] space and dissects toward either the [[Viscus|visceral]] pleura or the [[mediastinum]].
*A pneumothorax occurs when either the [[Viscus|visceral]] or the [[Mediastinum|mediastinal]] [[Pleural cavity|pleura]] ruptures that allows air to enter the [[Pleural cavity|pleural]] space.
 
==Genetics==
===Genetic association of familial primary sponatneous pneumothorax===
The [[Genetics|genetic]] association of familial primary sponatneous pneumothorax is as follows:<ref name="pmid16825879">{{cite journal| author=Chiu HT, Garcia CK| title=Familial spontaneous pneumothorax. | journal=Curr Opin Pulm Med | year= 2006 | volume= 12 | issue= 4 | pages= 268-72 | pmid=16825879 | doi=10.1097/01.mcp.0000230630.73139.f0 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16825879  }} </ref><ref name="pmid24812003">{{cite journal| author=Bintcliffe O, Maskell N| title=Spontaneous pneumothorax. | journal=BMJ | year= 2014 | volume= 348 | issue=  | pages= g2928 | pmid=24812003 | doi=10.1136/bmj.g2928 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=24812003  }} </ref><ref name="pmid19450320">{{cite journal| author=Wakai A| title=Spontaneous pneumothorax. | journal=BMJ Clin Evid | year= 2008 | volume= 2008 | issue=  | pages=  | pmid=19450320 | doi= | pmc=2907964 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=19450320  }} </ref><ref name="pmid21477390">{{cite journal| author=Wakai AP| title=Spontaneous pneumothorax. | journal=BMJ Clin Evid | year= 2011 | volume= 2011 | issue=  | pages=  | pmid=21477390 | doi= | pmc=3275306 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21477390  }} </ref><ref name="pmid7634863">{{cite journal| author=Andrivet P, Djedaini K, Teboul JL, Brochard L, Dreyfuss D| title=Spontaneous pneumothorax. Comparison of thoracic drainage vs immediate or delayed needle aspiration. | journal=Chest | year= 1995 | volume= 108 | issue= 2 | pages= 335-9 | pmid=7634863 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=7634863  }} </ref><ref name="pmid1864347">{{cite journal| author=Lippert HL, Lund O, Blegvad S, Larsen HV| title=Independent risk factors for cumulative recurrence rate after first spontaneous pneumothorax. | journal=Eur Respir J | year= 1991 | volume= 4 | issue= 3 | pages= 324-31 | pmid=1864347 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=1864347  }} </ref>
*Primary spontaneous pneumothorax can result as a mutation in the FLCN ([[folliculin]]) [[gene]].
*This [[gene]] codes for a [[protein]] called [[folliculin]].
*It is produced by the cells lining the [[Pulmonary alveolus|alveoli]] of the [[lung]].
*Folliculin is found in the connective tissue cells that allow the lungs to contract and expand while breathing.
*It plays a role in repairing the [[lung]] [[Tissue (biology)|tissue]] after damage.
*[[Nonsense mutation|Nonsense]] mutation in the [[folliculin]] gene results in isolated [[Family|familial]] sponataneous primary pneumothorax.<ref name="pmid15805188">{{cite journal| author=Graham RB, Nolasco M, Peterlin B, Garcia CK| title=Nonsense mutations in folliculin presenting as isolated familial spontaneous pneumothorax in adults. | journal=Am J Respir Crit Care Med | year= 2005 | volume= 172 | issue= 1 | pages= 39-44 | pmid=15805188 | doi=10.1164/rccm.200501-143OC | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=15805188  }} </ref>
*Altered [[folliculin]] protein can trigger the [[Inflammation|inflammatory]] process within the [[lung]] tissue that can alter and damage the [[Tissue (biology)|tissue]], resulting in [[Bleb|blebs]] formation.
 
==Associated Conditions==
Pneumothorax is associated with the following conditions:<ref name="pmid28744089">{{cite journal| author=Ray A, Gupta M| title=Iatrogenic buffalo-chest syndrome. | journal=Indian J Radiol Imaging | year= 2017 | volume= 27 | issue= 2 | pages= 254-255 | pmid=28744089 | doi=10.4103/0971-3026.209202 | pmc=5510326 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=28744089  }} </ref><ref name="pmid25879087">{{cite journal| author=Reading M| title=Bilateral pneumothoraces secondary to a Buffalo chest. | journal=Aust Crit Care | year= 2015 | volume= 28 | issue= 1 | pages= 10; discussion 54-5 | pmid=25879087 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=25879087  }} </ref>
*[[Homocystinuria]]
*[[Marfan's syndrome]]
**For [[Marfan's syndrome]] genetics, please [[Marfan's syndrome pathophysiology|click here]].
* [[Iatrogenesis|Iatrogenic]] buffalo [[chest]] [[syndrome]]
 
==Gross Pathology==
On gross [[pathology]], pneumothorax has the following findings:<ref name="KhanTsang2006">{{cite journal|last1=Khan|first1=Omar A.|last2=Tsang|first2=Geoffrey M.|last3=Barlow|first3=Clifford W.|last4=Amer|first4=Khalid M.|title=Routine Histological Analysis of Resected Lung Tissue in Primary Spontaneous Pneumothorax—Is It Justified?|journal=Heart, Lung and Circulation|volume=15|issue=2|year=2006|pages=137–138|issn=14439506|doi=10.1016/j.hlc.2005.10.007}}</ref><ref name="SchneiderMurali2014">{{cite journal|last1=Schneider|first1=Frank|last2=Murali|first2=Rajmohan|last3=Veraldi|first3=Kristen L.|last4=Tazelaar|first4=Henry D.|last5=Leslie|first5=Kevin O.|title=Approach to Lung Biopsies From Patients With Pneumothorax|journal=Archives of Pathology & Laboratory Medicine|volume=138|issue=2|year=2014|pages=257–265|issn=0003-9985|doi=10.5858/arpa.2013-0091-RA}}</ref>
 
*Bullae or [[Bleb|blebs]] on the [[Pleural cavity|pleural]] surface
 
*[[Pleural fibrosis]]
 
*Pleuropulmonary adhesions
 
*[[Airway]] [[inflammation]]
[[File:Bullae and Bleb.jpg|thumb|left|369x369px|Bleb [https://commons.wikimedia.org/wiki/File%3ABullae_and_Bleb.JPG Source:By Robertolyra (Own work), via Wikimedia Commons]]]
<br clear="left" />
 
==Microscopic Pathology==
*The microscopic findings associated with pneumothorax are as follows:<ref name="AyedChandrasekaran2006">{{cite journal|last1=Ayed|first1=Adel K.|last2=Chandrasekaran|first2=Chezhian|last3=Sukumar|first3=Murugan|title=Video-assisted thoracoscopic surgery for primary spontaneous pneumothorax: clinicopathological correlation|journal=European Journal of Cardio-Thoracic Surgery|volume=29|issue=2|year=2006|pages=221–225|issn=10107940|doi=10.1016/j.ejcts.2005.11.005}}</ref>
**[[Pleural fibrosis]] with [[Mesothelium|mesothelial]] thickening and [[hyperplasia]].
**[[Lymphocyte|Lymphocytes]], [[Eosinophil granulocyte|eosinophils]], [[Mesothelium|mesothelial]] thickening, and proliferation of the [[Pleural cavity|pleura]].
 
[[File:Lung bleb -- extremely low mag.jpg|thumb|left|369x369px|Lung Bleb [https://commons.wikimedia.org/wiki/File%3ALung_bleb_--_extremely_low_mag.jpg Source:By Nephron (Own work) [CC BY-SA 4.0 via Wikimedia Commons]]]
<br clear="left" />


==References==
==References==

Latest revision as of 22:01, 3 March 2018

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Feham Tariq, MD [2], Hamid Qazi, MD, BSc [3]

Overview

Pneumothorax is air in the pleural space under pressure resulting in lung collapse.The pathophysiology of each type depends on the underlying disease/etiology. Primary spontaneous pneumothorax most commonly results from the bleb (small air-filled lesions under pleural surface) rupture allowing the air to leak into the pleural space. A subclass of primary spontaneous pneumothorax is isolated familial primary spontaneous pneumothorax which is genetically associated with folliculin gene mutation. Secondary spontaneous pneumothorax occurs subsequent to underlying lung pathology such as obstructive lung disease, cystic fibrosis, diffuse parenchymal lung disease and lung cancer. In tension pneumothorax, the underlying pathophysiology most commonly is chest trauma forming a one-way valve in the pleura whereby air enters the pleural space when the pleural pressure is negative during inspiration. Pneumothorax can also result from several interventional procedures which cause penetrating or non-penetrating injury to the pleura resutling in abrupt increase in the alveolar pressure and hence, lead to alveolar rupture forming a communication with the pleura.

Pathophysiology

Anatomy and physiology of the thoracic cavity

The normal anatomy and physiology of thoracic cavity is as follows:

  • On either side of the cavity, a pleural membrane covers the outside surface of the lung (visceral pleura) and also lines the inside of the chest wall (parietal pleura).
  • The two layers are separated by a small amount of lubricating serous fluid known as the pleural fluid.
  • The lungs are fully inflated within the cavity as the pressure inside the airways is higher than the pressure inside the pleural space.
  • The inhaled air does not enter the pleural space as there is no natural connections between them as well as the pressure of gases in the blood stream is too low for them to be forced into the pleural space.
  • The pleural pressure is negative with respect to atmospheric pressure during spontaneous breathing.
  • Air can enter the pleural space through the following mechanisms:[4][5][6]
Pneumothorax Source:By National Heart Lung and Blood Institute, via Wikimedia Commons


Pathogenesis

The pathophysiology of pneumothorax depends on the underlying disease causing it.

Primary spontaneous pneumothorax

  • The most common underlying pathology of primary spontaneous pneumothorax is an apical subpleural bleb (small air-filled lesions under the pleural surface).[7]
  • In addition, smoking causes inflammation and obstruction of the small airways, which is responsible for the increased risk of primary spontaneous pneumothorax in smokers.

Secondary spontaneous pneumothorax

  • Pneumothorax due to underlying lung disease is secondary spontaneous pneumothorax.

Tension pneumothorax

  • The disruption occurs when a one-way valve forms, allowing air inflow into the pleural space, and prohibiting air outflow.
  • The volume of this nonabsorbable intrapleural air increases with each inspiration.
  • As a result, pressure rises within the affected hemithorax; ipsilateral lung collapses and causes hypoxia.
  • Further pressure causes the mediastinum shift toward the contralateral side and compresses both, the contralateral lung and the vasculature entering the right atrium of the heart.
  • This leads to worsening hypoxia and compromised venous return.

Iatrogenic pneumothorax

Following procedures commonly cause iatrogenic pneumothorax:[10][11]

Mechanism of injury:

Genetics

Genetic association of familial primary sponatneous pneumothorax

The genetic association of familial primary sponatneous pneumothorax is as follows:[15][16][17][18][19][20]

  • Primary spontaneous pneumothorax can result as a mutation in the FLCN (folliculin) gene.
  • This gene codes for a protein called folliculin.
  • It is produced by the cells lining the alveoli of the lung.
  • Folliculin is found in the connective tissue cells that allow the lungs to contract and expand while breathing.
  • It plays a role in repairing the lung tissue after damage.
  • Nonsense mutation in the folliculin gene results in isolated familial sponataneous primary pneumothorax.[21]
  • Altered folliculin protein can trigger the inflammatory process within the lung tissue that can alter and damage the tissue, resulting in blebs formation.

Associated Conditions

Pneumothorax is associated with the following conditions:[22][23]

Gross Pathology

On gross pathology, pneumothorax has the following findings:[24][25]

  • Pleuropulmonary adhesions
Bleb Source:By Robertolyra (Own work), via Wikimedia Commons


Microscopic Pathology

Lung Bleb Source:By Nephron (Own work) [CC BY-SA 4.0 via Wikimedia Commons


References

  1. Grundy S, Bentley A, Tschopp JM (2012). "Primary spontaneous pneumothorax: a diffuse disease of the pleura". Respiration. 83 (3): 185–9. doi:10.1159/000335993. PMID https://www.ncbi.nlm.nih.gov/pubmed/22343477 Check |pmid= value (help).
  2. Lee SC, Cheng YL, Huang CW, Tzao C, Hsu HH, Chang H (2008). "Simultaneous bilateral primary spontaneous pneumothorax". Respirology. 13 (1): 145–8. doi:10.1111/j.1440-1843.2007.01168.x. PMID 18197926.
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