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== Overview ==
== Overview ==
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V/Q mismatch can be caused by various diseases and a workup must be done for diagnosis and treatment.
V/Q mismatch can be caused by various diseases and a workup must be done for diagnosis and treatment.
*Labs:
*Labs:
** Arterial Blood Gas
** [[Arterial Blood Gas]]
**PAO2
**[[PAO2]]
**PaO2
**[[PaO2]]
**PaCo2
**[[PaCo2]]
** Bicarbonate levels
**[[Bicarbonate levels]]
**DLCO2
**[[DLCO2]]
**Spirometry
**[[Spirometry]]


*Imaging
*Imaging
**Chest X-Ray
**[[Chest X-Ray]]
** Ventilation-Perfusion scan
**[[Ventilation-Perfusion scan]]
    
    
   
   

Latest revision as of 14:13, 6 March 2019

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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 and patency 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.

Causes

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

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. Anything that affects the blood flow and oxygenation in the lung can cause a V/Q mismatch. 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.[15] [16] 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.[17]

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. For example:

  • Pulmonary fibrosis can present with a honeycomb appearance of the lung [34]
  • Pulmonary infarct can present as a wedge shaped infarct [35]

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[36]
  • In Interstitial lung disease caused by asbestosis ferruginous bodies may be present [37]

Understanding V/Q mismatch in the context of hypoxia

There are two causes of V/Q mismatch:

  1. Decreased Ventilation
  2. Decreased Perfusion

Shunts

Pulmonary shunts occur when the V/Q ratio is zero. It is formed when there is absent ventilation in one part of the lung with normal perfusion. [38][39] This deoxygenated blood enters arterial circulation without getting oxygenated in the lung. Absorptive or compressive pulmonary atelectasis is the major reason for shunt formation. Pulmonary AV malformation, hepatopulmonary syndrome [40], ARDS, and pulmonary edema are less common causes. Shunting is characterized by it poor response to 100% oxygen therapy.

Dead space ventilation

Dead space ventilation occurs when V/Q ratio is undefined. When blood supply to part of the lung is cut off, oxygen in the ventilated atmospheric air is not able to enter the bloodstream leading to lesser overall efficiency of the alveolar oxygenation mechanism. [41] Pulmonary Embolism is the most common cause of dead space ventilation.[42] Hypoxemia caused by dead space ventilation will improve with 100% oxygen therapy.

Natural History and Complications

If left untreated patients with V/Q mismatch may progress to develop pulmonary hypertension [43], respiratory failure, and even death. [44] [45] In patients with an decreased V/Q ratio, 100% oxygen can be used as acute treatment while additional diagnostic studies are necessary to determine the underlying cause.[46] Prognosis, mortality and survival rate of patients with V/Q mismatch depend on the underlying cause and early treatment.[47]

History, Symptoms, and Physical Exam

Symptoms of V/Q mismatch depend on the underlying cause but in general a majority of cases with V/Q mismatch include:

Patients with V/Q mismatch usually appear distressed. Physical examination of patients with V/Q mismatch depends on the underlying cause. Some common physical examination findings of V/Q mismatch include:

If the patient is in respiratory failure they may present with:

Differential Diagnosis

V/Q mismatch is finding that can be indicative of a serious respiratory disease. The differential diagnosis for V/Q mismatch includes:

A workup must be done to diagnose and treat the underlying illness

Work up

V/Q mismatch can be caused by various diseases and a workup must be done for diagnosis and treatment.


Calculations using measurements from Arterial Blood Gas (ABG) and the response of those measures to supplemental oxygen are used to investigate the cause of hypoxia.

Physiological changes in Alveolar and Blood gas in various causes of hypoxia
Cause P(Alv)O2 A-a gradient Response to

supplemental oxygen

Diffusion limitation Normal Increased Improved PaO2
Hypoventilation Reduced Normal Improved PaO2
Reduced PiO2 Reduced Normal Improved PaO2
Shunt formation Reduced in local areas of lung Increased Improved PaO2
Dead space formation Normal Increased Minimal to no improvement

PiO2 - partial pressure of oxygen in inspired air

P(Alv)O2 - partial pressure of oxygen in alveolar air

PaO2 - partial pressure of oxygen in arterial air

A-a gradient - P(Alv)O2 - PaO2

References

  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. ↑ 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)
  5. ↑ 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)
  6. ↑ 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)
  7. ↑ Natan Cramer, Roger S.. Taylor & Melissa M.. Tavarez (2018). "Foreign Body Aspiration". PMID 30285375. Unknown parameter |month= ignored (help)
  8. ↑ 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)
  9. ↑ 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)
  10. ↑ 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)
  11. ↑ 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)
  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. ↑ 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)
  14. ↑ 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)
  15. ↑ 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)
  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. ↑ 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)
  19. ↑ 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)
  20. ↑ 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)
  21. ↑ Natan Cramer, Roger S.. Taylor & Melissa M.. Tavarez (2018). "Foreign Body Aspiration". PMID 30285375. Unknown parameter |month= ignored (help)
  22. ↑ Zulkifli Amin, Hilman Zulkifli Amin & Nadim Marchian Tedyanto (2016). "Hepatopulmonary Syndrome: A Brief Review". Romanian journal of internal medicine = Revue roumaine de medecine interne. 54 (2): 93–97. doi:10.1515/rjim-2016-0015. PMID 27352437. Unknown parameter |month= ignored (help)
  23. ↑ 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)
  24. ↑ 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)
  25. ↑ 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)
  26. ↑ 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)
  27. ↑ 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)
  28. ↑ 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)
  29. ↑ 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)
  30. ↑ 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)
  31. ↑ 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)
  32. ↑ 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)
  33. ↑ 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)
  34. ↑ Hiroaki Arakawa & Koichi Honma (2011). "Honeycomb lung: history and current concepts". AJR. American journal of roentgenology. 196 (4): 773–782. doi:10.2214/AJR.10.4873. PMID 21427324. Unknown parameter |month= ignored (help)
  35. ↑ Massimo Miniati, Matteo Bottai, Cesario Ciccotosto, Luca Roberto & Simonetta Monti (2015). "Predictors of Pulmonary Infarction". Medicine. 94 (41): e1488. doi:10.1097/MD.0000000000001488. PMID 26469892. Unknown parameter |month= ignored (help)
  36. ↑ P. J. Dor, S. J. Ackerman & G. J. Gleich (1984). "Charcot-Leyden crystal protein and eosinophil granule major basic protein in sputum of patients with respiratory diseases". The American review of respiratory disease. 130 (6): 1072–1077. doi:10.1164/arrd.1984.130.6.1072. PMID 6508005. Unknown parameter |month= ignored (help)
  37. ↑ A. M. Churg & M. L. Warnock (1981). "Asbestos and other ferruginous bodies: their formation and clinical significance". The American journal of pathology. 102 (3): 447–456. PMID 6101235. Unknown parameter |month= ignored (help)
  38. ↑ 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)
  39. ↑ 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)
  40. ↑ Zulkifli Amin, Hilman Zulkifli Amin & Nadim Marchian Tedyanto (2016). "Hepatopulmonary Syndrome: A Brief Review". Romanian journal of internal medicine = Revue roumaine de medecine interne. 54 (2): 93–97. doi:10.1515/rjim-2016-0015. PMID 27352437. Unknown parameter |month= ignored (help)
  41. ↑ Sal Intagliata & Alessandra Rizzo (2018). "Physiology, Lung Dead Space". PMID 29494107. Unknown parameter |month= ignored (help)
  42. ↑ 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)
  43. ↑ Michael Y. Shino, Joseph P. 3rd Lynch, Rajeev Saggar, Fereidoun Abtin, John A. Belperio & Rajan Saggar (2013). "Pulmonary hypertension complicating interstitial lung disease and COPD". Seminars in respiratory and critical care medicine. 34 (5): 600–619. doi:10.1055/s-0033-1356548. PMID 24037628. Unknown parameter |month= ignored (help)
  44. ↑ Kelly Stam, Richard W. B. van Duin, Andre Uitterdijk, Ilona Krabbendam-Peters, Oana Sorop, A. H. Jan Danser, Dirk J. Duncker & Daphne Merkus (2018). "Pulmonary microvascular remodeling in chronic thrombo-embolic pulmonary hypertension". American journal of physiology. Lung cellular and molecular physiology. doi:10.1152/ajplung.00043.2018. PMID 30260284. Unknown parameter |month= ignored (help)
  45. ↑ 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)
  46. ↑ 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)
  47. ↑ Brian N. Jobse, Cory Ajr McCurry, Mathieu C. Morissette, Rod G. Rhem, Martin R. Stampfli & Nancy Renee Labiris (2014). "Impact of inflammation, emphysema, and smoking cessation on V/Q in mouse models of lung obstruction". Respiratory research. 15: 42. doi:10.1186/1465-9921-15-42. PMID 24730756. Unknown parameter |month= ignored (help)
  48. ↑ 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)
  49. ↑ 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)
  50. ↑ 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)
  51. ↑ Natan Cramer, Roger S.. Taylor & Melissa M.. Tavarez (2018). "Foreign Body Aspiration". PMID 30285375. Unknown parameter |month= ignored (help)
  52. ↑ Zulkifli Amin, Hilman Zulkifli Amin & Nadim Marchian Tedyanto (2016). "Hepatopulmonary Syndrome: A Brief Review". Romanian journal of internal medicine = Revue roumaine de medecine interne. 54 (2): 93–97. doi:10.1515/rjim-2016-0015. PMID 27352437. Unknown parameter |month= ignored (help)
  53. ↑ 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)
  54. ↑ 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)
  55. ↑ 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)
  56. ↑ 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)
  57. ↑ 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)
  58. ↑ 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)
  59. ↑ 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)
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