Ventilation-perfusion mismatch pathophysiology: Difference between revisions
| Line 16: | Line 16: | ||
Some conditions that cause decrease in V/Q are: | Some conditions that cause decrease in V/Q are: | ||
* [[Bronchitis]] | * [[Bronchitis]] | ||
* [[Asthma]] | * [[Asthma]]<ref>{{Cite journal | ||
| author = [[Krishnan Parameswaran]], [[Andrew C. Knight]], [[Niall P. Keaney]], [[E. David Williams]] & [[Ian K. Taylor]] | |||
| title = Ventilation and perfusion lung scintigraphy of allergen-induced airway responses in atopic asthmatic subjects | |||
| journal = [[Canadian respiratory journal]] | |||
| volume = 14 | |||
| issue = 5 | |||
| pages = 285–291 | |||
| year = 2007 | |||
| month = July-August | |||
| doi = 10.1155/2007/474202 | |||
| pmid = 17703244 | |||
}}</ref> | |||
* [[Foreign body aspiration]] | * [[Foreign body aspiration]] | ||
* [[Hepatopulmonary syndrome]] | * [[Hepatopulmonary syndrome]] | ||
Revision as of 19:39, 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. 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.
- ↑ 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) - ↑ 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)