Ventilation-perfusion mismatch pathophysiology: Difference between revisions

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==Overview==
==Overview==
Any discrepancy between pulmonary blood flow and [[ventilation]] is called V/Q mismatch. Ideally [[Ventilation (physiology)|ventilation]] and [[perfusion]] should be equal with a V/Q ratio of 1, but the normal lung varies due to a higher perfusion at the [[Base of lung|base of the lung]] than the [[Apex of lung|apex of the lung]]. This causes a higher V/Q ratio at the apex compared to the base.<ref>{{Cite journal
In normal lung physiology the [[V/Q ratio]] is a measurement used to determine the efficacy and adequacy of [[ventilation]] and [[perfusion]] of the lung. [[Ventilation]] is the amount of air that reaches the lungs and [[Perfusion]] is the amount of blood flow to the lung. Any discrepancy between pulmonary blood flow and [[ventilation]] is called V/Q mismatch. Ideally [[Ventilation (physiology)|ventilation]] and [[perfusion]] should be equal with a V/Q ratio of 1, but the normal lung varies due to multiple factors such as gravity, size of airways, and positioning. There is a higher perfusion at the [[Base of lung|base of the lung]] than the [[Apex of lung|apex of the lung]]. This causes a higher V/Q ratio at the apex compared to the base.<ref>{{Cite journal
  | author = [[Malay Sarkar]], [[N. Niranjan]] & [[P. K. Banyal]]
  | author = [[Marcelo Alcantara Holanda]], [[Nathalia Parente de Sousa]], [[Luana Torres Melo]], [[Liegina Silveira Marinho]], [[Helder Veras Ribeiro-Filho]], [[Luiz Ernesto de Almeida Troncon]], [[Vasco Pinheiro Diogenes Bastos]], [[Armenio Aguiar Dos Santos]] & [[Rodrigo Jose Bezerra de Siqueira]]
  | title = Mechanisms of hypoxemia
| title = Helping students to understand physiological aspects of regional distribution of ventilation in humans: a experience from the electrical impedance tomography
  | journal = [[Lung India : official organ of Indian Chest Society]]
| journal = [[Advances in physiology education]]
  | volume = 34
| volume = 42
  | issue = 1
| issue = 4
  | pages = 47–60
| pages = 655–660
  | year = 2017
| year = 2018
  | month = January-February
| month = December
  | doi = 10.4103/0970-2113.197116
| doi = 10.1152/advan.00086.2018
  | pmid = 28144061
| pmid = 30387699
}}</ref> The average V/Q ratio in a normal lung is about 0.8, with about 4 liters of oxygen and 5 liters of blood entering the lung per minute. Diseased lung can cause a V/Q mismatch due to decreased blood flow or oxygenation.  This results in [[hypoxemia]], and there are many causes of it.
}}</ref><ref>{{Cite journal
| author = [[Johan Petersson]] & [[Robb W. Glenny]]
  | title = Gas exchange and ventilation-perfusion relationships in the lung
  | journal = [[The European respiratory journal]]
  | volume = 44
  | issue = 4
  | pages = 1023–1041
  | year = 2014
  | month = October
  | doi = 10.1183/09031936.00037014
  | pmid = 25063240
}}</ref>The average V/Q ratio in a normal lung is about 0.8, with about 4 liters of oxygen and 5 liters of blood entering the lung per minute.<ref>http://www.rnceus.com/abgs/abgvq.html</ref>Diseased lung can cause a V/Q mismatch due to decreased blood flow or oxygenation.  This results in [[hypoxemia]], which is a decreased oxygen concentration of blood.


==Pathogenesis==
==Pathogenesis==
V/Q mismatch is one of the most common reasons of hypoxemia in patients with [[lung]] diseases like [[Obstructive lung disease|obstructive lung]] diseases, pulmonary vascular diseases, and [[Interstitial lung disease|interstitial diseases]] .  An increased V/Q mismatch is caused by a decrease in blood flow to the lung, for example a [[pulmonary embolism]]. A decreased V/Q mismatch is caused by a decrease in ventilation or an airway obstruction, for example [[Asthma]]. A V/Q mismatch  due to a perfusion defect will improve with 100% [[Oxygen therapy|oxygen therapy.]]   
V/Q mismatch is one of the most common causes of hypoxemia. It can be caused by [[Obstructive lung disease|obstructive lung]] diseases, pulmonary vascular diseases, and [[Interstitial lung disease|interstitial diseases]] .  An increased V/Q mismatch is caused by a decrease in blood flow to the lung, for example a [[pulmonary embolism]]. A decreased V/Q mismatch is caused by a decrease in ventilation or an airway obstruction, for example [[Asthma]]. A V/Q mismatch  due to a perfusion defect will improve with 100% [[Oxygen therapy|oxygen therapy.]]<ref>{{Cite journal
 
| author = [[Vu M. Mai]], [[Benjamin Liu]], [[Jason A. Polzin]], [[Wei Li]], [[Saban Kurucay]], [[Alexander A. Bankier]], [[Jack Knight-Scott]], [[Priti Madhav]], [[Robert R. Edelman]] & [[Qun Chen]]
In normal condition when there is a low ventilation, the body tries to keep this ratio in a normal range by restricting the perfusion in that specific area of the lung. This unique mechanism is called hypoxic pulmonary vasoconstriction. If this process continues for a long time it can cause pulmonary hypertension .  
| title = Ventilation-perfusion ratio of signal intensity in human lung using oxygen-enhanced and arterial spin labeling techniques
| journal = [[Magnetic resonance in medicine]]
| volume = 48
| issue = 2
| pages = 341–350
| year = 2002
| month = August
| doi = 10.1002/mrm.10230
| pmid = 12210943
}}</ref> <ref>{{Cite journal
| author = [[Johan Petersson]] & [[Robb W. Glenny]]
  | title = Gas exchange and ventilation-perfusion relationships in the lung
| journal = [[The European respiratory journal]]
| volume = 44
| issue = 4
| pages = 1023–1041
| year = 2014
| month = October
| doi = 10.1183/09031936.00037014
| pmid = 25063240
}}</ref> In normal conditions when there is a low ventilation, the body tries to keep this ratio in a normal range by restricting the perfusion in that specific area of the lung. This unique mechanism is called hypoxic pulmonary vasoconstriction. If this process continues for a long time it can cause pulmonary hypertension.<ref>{{Cite journal
| author = [[Johan Petersson]] & [[Robb W. Glenny]]
| title = Gas exchange and ventilation-perfusion relationships in the lung
| journal = [[The European respiratory journal]]
| volume = 44
| issue = 4
| pages = 1023–1041
| year = 2014
| month = October
| doi = 10.1183/09031936.00037014
| pmid = 25063240
}}</ref>


==Associated Conditions==
==Associated Conditions==
Line 37: Line 79:
  | doi = 10.1183/09031936.00037014
  | doi = 10.1183/09031936.00037014
  | pmid = 25063240
  | pmid = 25063240
}}</ref><ref>{{Cite journal
| author = [[Kelvin Hsu]], [[Jonathan P. Williamson]], [[Matthew J. Peters]] & [[Alvin J. Ing]]
| title = Endoscopic Lung Volume Reduction in COPD: Improvements in Gas Transfer Capacity Are Associated With Improvements in Ventilation and Perfusion Matching
| journal = [[Journal of bronchology & interventional pulmonology]]
| volume = 25
| issue = 1
| pages = 48–53
| year = 2018
| month = January
| doi = 10.1097/LBR.0000000000000445
| pmid = 29261579
}}</ref>
}}</ref>
* [[Asthma]]<ref>{{Cite journal
* [[Asthma]]<ref>{{Cite journal
Line 50: Line 103:
  | pmid = 17703244
  | pmid = 17703244
}}</ref>
}}</ref>
* [[Foreign body aspiration]]
* [[Foreign body aspiration]]<ref>{{Cite journal
| author = [[Natan Cramer]], [[Roger S.. Taylor]] & [[Melissa M.. Tavarez]]
| title = Foreign Body Aspiration
| year = 2018
| month = January
| pmid = 30285375
}}</ref>
* [[Hepatopulmonary syndrome]]
* [[Hepatopulmonary syndrome]]
* [[ARDS]]
* [[ARDS]]<ref>{{Cite journal
| author = [[Johan Petersson]] & [[Robb W. Glenny]]
| title = Gas exchange and ventilation-perfusion relationships in the lung
| journal = [[The European respiratory journal]]
| volume = 44
| issue = 4
| pages = 1023–1041
| year = 2014
| month = October
| doi = 10.1183/09031936.00037014
| pmid = 25063240
}}</ref>
* Bronchiectasis<ref>{{Cite journal
| author = [[Malay Sarkar]], [[N. Niranjan]] & [[P. K. Banyal]]
| title = Mechanisms of hypoxemia
| journal = [[Lung India : official organ of Indian Chest Society]]
| volume = 34
| issue = 1
| pages = 47–60
| year = 2017
| month = January-February
| doi = 10.4103/0970-2113.197116
| pmid = 28144061
}}</ref>
* Interstitial Lung disease<ref>{{Cite journal
| author = [[Malay Sarkar]], [[N. Niranjan]] & [[P. K. Banyal]]
| title = Mechanisms of hypoxemia
| journal = [[Lung India : official organ of Indian Chest Society]]
| volume = 34
| issue = 1
| pages = 47–60
| year = 2017
| month = January-February
| doi = 10.4103/0970-2113.197116
| pmid = 28144061
}}</ref>
* Cystic Fibrosis<ref>{{Cite journal
| author = [[Malay Sarkar]], [[N. Niranjan]] & [[P. K. Banyal]]
| title = Mechanisms of hypoxemia
| journal = [[Lung India : official organ of Indian Chest Society]]
| volume = 34
| issue = 1
| pages = 47–60
| year = 2017
| month = January-February
| doi = 10.4103/0970-2113.197116
| pmid = 28144061
}}</ref>
* Pulmonary Hypertension<ref>{{Cite journal
| author = [[Malay Sarkar]], [[N. Niranjan]] & [[P. K. Banyal]]
| title = Mechanisms of hypoxemia
| journal = [[Lung India : official organ of Indian Chest Society]]
| volume = 34
| issue = 1
| pages = 47–60
| year = 2017
| month = January-February
| doi = 10.4103/0970-2113.197116
| pmid = 28144061
}}</ref>
Some conditions that cause increase in V/Q are:
Some conditions that cause increase in V/Q are:
* [[Pulmonary embolism]]<ref>{{Cite journal
* [[Pulmonary embolism]]<ref>{{Cite journal
Line 78: Line 196:
  | pmid = 25063240
  | pmid = 25063240
}}</ref>
}}</ref>
Extreme conditions:
* An area of no ventilation is termed a shunt
**V/Q ratio= 0
* An area of no perfusion is termed a dead space
**V/Q ratio is undefined


==Genetics==
==Genetics==
The association between V/Q mismatch and genetic depends on the etiology of the mismatch. For example ''ORMDL3'' and ''GSDML'' genes play a role in causing [[asthma]] .  
The association between V/Q mismatch and genetics depends on the etiology of the mismatch. Some diseases with genetic components include:
*[[Asthma]] has over 100 genetic associations.<ref>{{Cite journal
| author = [[C. Ober]] & [[S. Hoffjan]]
| title = Asthma genetics 2006: the long and winding road to gene discovery
| journal = [[Genes and immunity]]
| volume = 7
| issue = 2
| pages = 95–100
| year = 2006
| month = March
| doi = 10.1038/sj.gene.6364284
| pmid = 16395390
}}</ref>
*[[Emphysema]] can be associated with a deficiency of alpha 1 antitrypsin <ref>{{Cite journal
| author = [[James J. Tasch]], [[Ann T. McLaughlan]] & [[Asad A. Nasir]]
| title = A Novel Approach to Screening for Alpha-1 Antitrypsin Deficiency: Inpatient Testing at a Teaching Institution
| journal = [[Chronic obstructive pulmonary diseases (Miami, Fla.)]]
| volume = 5
| issue = 2
| pages = 106–110
| year = 2018
| month = April
| doi = 10.15326/jcopdf.5.2.2017.0170
| pmid = 30374448
}}</ref>
*[[Cystic fibrosis]] is a genetic disorder affecting chloride transporters <ref>{{Cite journal
| author = [[Shuzhong Zhang]], [[Chandra L. Shrestha]] & [[Benjamin T. Kopp]]
| title = Cystic fibrosis transmembrane conductance regulator (CFTR) modulators have differential effects on cystic fibrosis macrophage function
| journal = [[Scientific reports]]
| volume = 8
| issue = 1
| pages = 17066
| year = 2018
| month = November
| doi = 10.1038/s41598-018-35151-7
| pmid = 30459435
}}</ref><ref>{{Cite journal
| author = [[Zhe Zhang]], [[Fangyu Liu]] & [[Jue Chen]]
| title = Molecular structure of the ATP-bound, phosphorylated human CFTR
| journal = [[Proceedings of the National Academy of Sciences of the United States of America]]
| year = 2018
| month = November
| doi = 10.1073/pnas.1815287115
| pmid = 30459277
}}</ref>


== Gross Pathology ==
== Gross Pathology ==
The gross pathology depends on the exact reason for the V/Q mismatch.
The gross pathology depends on the exact reason for the V/Q mismatch.
V/Q mismatch can be seen on a [[Ventilation perfusion scan]].


== Microscopic Pathology ==
== Microscopic Pathology ==
The microscopic pathology depends on the exact reason for the V/Q mismatch. For example in [[asthma]] there are extracellular Charcot-Leyden crystals and increased mucosal [[Goblet cell|goblet]] cells.
The microscopic pathology depends on the exact reason for the V/Q mismatch. For example in [[asthma]] there are extracellular Charcot-Leyden crystals and increased mucosal [[Goblet cell|goblet]] cells.
<references />
<references />

Latest revision as of 02:36, 29 November 2018


Template:Ventilation-perfusion mismatch

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aida Javanbakht, M.D.

Overview

In normal lung physiology the V/Q ratio is a measurement used to determine the efficacy and adequacy of ventilation and perfusion of the lung. Ventilation is the amount of air that reaches the lungs and Perfusion is the amount of blood flow to the lung. Any discrepancy between pulmonary blood flow and ventilation is called V/Q mismatch. Ideally ventilation and perfusion should be equal with a V/Q ratio of 1, but the normal lung varies due to multiple factors such as gravity, size of airways, and positioning. There is a higher perfusion at the base of the lung than the apex of the lung. This causes a higher V/Q ratio at the apex compared to the base.[1][2]The average V/Q ratio in a normal lung is about 0.8, with about 4 liters of oxygen and 5 liters of blood entering the lung per minute.[3]Diseased lung can cause a V/Q mismatch due to decreased blood flow or oxygenation. This results in hypoxemia, which is a decreased oxygen concentration of blood.

Pathogenesis

V/Q mismatch is one of the most common causes of hypoxemia. It can be caused by obstructive lung diseases, pulmonary vascular diseases, and interstitial diseases . An increased V/Q mismatch is caused by a decrease in blood flow to the lung, for example a pulmonary embolism. A decreased V/Q mismatch is caused by a decrease in ventilation or an airway obstruction, for example Asthma. A V/Q mismatch due to a perfusion defect will improve with 100% oxygen therapy.[4] [5] In normal conditions when there is a low ventilation, the body tries to keep this ratio in a normal range by restricting the perfusion in that specific area of the lung. This unique mechanism is called hypoxic pulmonary vasoconstriction. If this process continues for a long time it can cause pulmonary hypertension.[6]

Associated Conditions

Some conditions that cause decrease in V/Q are:

Some conditions that cause increase in V/Q are:


Extreme conditions:

  • An area of no ventilation is termed a shunt
    • V/Q ratio= 0
  • An area of no perfusion is termed a dead space
    • V/Q ratio is undefined

Genetics

The association between V/Q mismatch and genetics depends on the etiology of the mismatch. Some diseases with genetic components include:

Gross Pathology

The gross pathology depends on the exact reason for the V/Q mismatch. V/Q mismatch can be seen on a Ventilation perfusion scan.

Microscopic Pathology

The microscopic pathology depends on the exact reason for the V/Q mismatch. For example in asthma there are extracellular Charcot-Leyden crystals and increased mucosal goblet cells.

  1. ↑ Marcelo Alcantara Holanda, Nathalia Parente de Sousa, Luana Torres Melo, Liegina Silveira Marinho, Helder Veras Ribeiro-Filho, Luiz Ernesto de Almeida Troncon, Vasco Pinheiro Diogenes Bastos, Armenio Aguiar Dos Santos & Rodrigo Jose Bezerra de Siqueira (2018). "Helping students to understand physiological aspects of regional distribution of ventilation in humans: a experience from the electrical impedance tomography". Advances in physiology education. 42 (4): 655–660. doi:10.1152/advan.00086.2018. PMID 30387699. Unknown parameter |month= ignored (help)
  2. ↑ Johan Petersson & Robb W. Glenny (2014). "Gas exchange and ventilation-perfusion relationships in the lung". The European respiratory journal. 44 (4): 1023–1041. doi:10.1183/09031936.00037014. PMID 25063240. Unknown parameter |month= ignored (help)
  3. ↑ http://www.rnceus.com/abgs/abgvq.html
  4. ↑ Vu M. Mai, Benjamin Liu, Jason A. Polzin, Wei Li, Saban Kurucay, Alexander A. Bankier, Jack Knight-Scott, Priti Madhav, Robert R. Edelman & Qun Chen (2002). "Ventilation-perfusion ratio of signal intensity in human lung using oxygen-enhanced and arterial spin labeling techniques". Magnetic resonance in medicine. 48 (2): 341–350. doi:10.1002/mrm.10230. PMID 12210943. Unknown parameter |month= ignored (help)
  5. ↑ Johan Petersson & Robb W. Glenny (2014). "Gas exchange and ventilation-perfusion relationships in the lung". The European respiratory journal. 44 (4): 1023–1041. doi:10.1183/09031936.00037014. PMID 25063240. Unknown parameter |month= ignored (help)
  6. ↑ Johan Petersson & Robb W. Glenny (2014). "Gas exchange and ventilation-perfusion relationships in the lung". The European respiratory journal. 44 (4): 1023–1041. doi:10.1183/09031936.00037014. PMID 25063240. Unknown parameter |month= ignored (help)
  7. ↑ Johan Petersson & Robb W. Glenny (2014). "Gas exchange and ventilation-perfusion relationships in the lung". The European respiratory journal. 44 (4): 1023–1041. doi:10.1183/09031936.00037014. PMID 25063240. Unknown parameter |month= ignored (help)
  8. ↑ Kelvin Hsu, Jonathan P. Williamson, Matthew J. Peters & Alvin J. Ing (2018). "Endoscopic Lung Volume Reduction in COPD: Improvements in Gas Transfer Capacity Are Associated With Improvements in Ventilation and Perfusion Matching". Journal of bronchology & interventional pulmonology. 25 (1): 48–53. doi:10.1097/LBR.0000000000000445. PMID 29261579. Unknown parameter |month= ignored (help)
  9. ↑ Krishnan Parameswaran, Andrew C. Knight, Niall P. Keaney, E. David Williams & Ian K. Taylor (2007). "Ventilation and perfusion lung scintigraphy of allergen-induced airway responses in atopic asthmatic subjects". Canadian respiratory journal. 14 (5): 285–291. doi:10.1155/2007/474202. PMID 17703244. Unknown parameter |month= ignored (help)
  10. ↑ Natan Cramer, Roger S.. Taylor & Melissa M.. Tavarez (2018). "Foreign Body Aspiration". PMID 30285375. Unknown parameter |month= ignored (help)
  11. ↑ Johan Petersson & Robb W. Glenny (2014). "Gas exchange and ventilation-perfusion relationships in the lung". The European respiratory journal. 44 (4): 1023–1041. doi:10.1183/09031936.00037014. PMID 25063240. Unknown parameter |month= ignored (help)
  12. ↑ Malay Sarkar, N. Niranjan & P. K. Banyal (2017). "Mechanisms of hypoxemia". Lung India : official organ of Indian Chest Society. 34 (1): 47–60. doi:10.4103/0970-2113.197116. PMID 28144061. Unknown parameter |month= ignored (help)
  13. ↑ Malay Sarkar, N. Niranjan & P. K. Banyal (2017). "Mechanisms of hypoxemia". Lung India : official organ of Indian Chest Society. 34 (1): 47–60. doi:10.4103/0970-2113.197116. PMID 28144061. Unknown parameter |month= ignored (help)
  14. ↑ Malay Sarkar, N. Niranjan & P. K. Banyal (2017). "Mechanisms of hypoxemia". Lung India : official organ of Indian Chest Society. 34 (1): 47–60. doi:10.4103/0970-2113.197116. PMID 28144061. Unknown parameter |month= ignored (help)
  15. ↑ Malay Sarkar, N. Niranjan & P. K. Banyal (2017). "Mechanisms of hypoxemia". Lung India : official organ of Indian Chest Society. 34 (1): 47–60. doi:10.4103/0970-2113.197116. PMID 28144061. Unknown parameter |month= ignored (help)
  16. ↑ Johan Petersson & Robb W. Glenny (2014). "Gas exchange and ventilation-perfusion relationships in the lung". The European respiratory journal. 44 (4): 1023–1041. doi:10.1183/09031936.00037014. PMID 25063240. Unknown parameter |month= ignored (help)
  17. ↑ Johan Petersson & Robb W. Glenny (2014). "Gas exchange and ventilation-perfusion relationships in the lung". The European respiratory journal. 44 (4): 1023–1041. doi:10.1183/09031936.00037014. PMID 25063240. Unknown parameter |month= ignored (help)
  18. ↑ C. Ober & S. Hoffjan (2006). "Asthma genetics 2006: the long and winding road to gene discovery". Genes and immunity. 7 (2): 95–100. doi:10.1038/sj.gene.6364284. PMID 16395390. Unknown parameter |month= ignored (help)
  19. ↑ James J. Tasch, Ann T. McLaughlan & Asad A. Nasir (2018). "A Novel Approach to Screening for Alpha-1 Antitrypsin Deficiency: Inpatient Testing at a Teaching Institution". Chronic obstructive pulmonary diseases (Miami, Fla.). 5 (2): 106–110. doi:10.15326/jcopdf.5.2.2017.0170. PMID 30374448. Unknown parameter |month= ignored (help)
  20. ↑ Shuzhong Zhang, Chandra L. Shrestha & Benjamin T. Kopp (2018). "Cystic fibrosis transmembrane conductance regulator (CFTR) modulators have differential effects on cystic fibrosis macrophage function". Scientific reports. 8 (1): 17066. doi:10.1038/s41598-018-35151-7. PMID 30459435. Unknown parameter |month= ignored (help)
  21. ↑ Zhe Zhang, Fangyu Liu & Jue Chen (2018). "Molecular structure of the ATP-bound, phosphorylated human CFTR". Proceedings of the National Academy of Sciences of the United States of America. doi:10.1073/pnas.1815287115. PMID 30459277. Unknown parameter |month= ignored (help)
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