Ventilation-perfusion mismatch pathophysiology: Difference between revisions
| Line 61: | Line 61: | ||
| 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]] | ||
Revision as of 22:26, 25 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
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 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] 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.
Pathogenesis
V/Q mismatch is one of the most common reasons of hypoxemia in patients with lung diseases like 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.
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 .
Associated Conditions
Some conditions that cause decrease in V/Q are:
Some conditions that cause increase in V/Q are:
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 .
Gross Pathology
The gross pathology depends on the exact reason for the V/Q mismatch.
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.
- ↑ 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) - ↑ 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) - ↑ 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) - ↑ 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) - ↑ Natan Cramer, Roger S.. Taylor & Melissa M.. Tavarez (2018). "Foreign Body Aspiration". PMID 30285375. Unknown parameter
|month=ignored (help) - ↑ 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) - ↑ 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)