Table of ContentsView AllTable of ContentsSymptomsCausesDiagnosisTreatment
Table of ContentsView All
View All
Table of Contents
Symptoms
Causes
Diagnosis
Treatment
Ventilation-perfusion (V/Q) mismatch occurs when either the ventilation (airflow) or perfusion (blood flow) in the lungs is impaired, preventing the lungs from optimally delivering oxygen to the blood. This can cause shortness of breath, lightheadedness, or loss of consciousness, and occur due to chronic lung diseases (e.g., bronchitis) or a sudden lung impairment (e.g.,pulmonary embolus).
Jessica Olah / Verywell
V/Q Mismatch Symptoms
V/Q mismatch develops as a chronic lung disease progresses. The effects of V/Q mismatch can vary depending on the severity of its cause and the discrepancy between blood circulation and airflow in the lungs.
Common symptoms associated with V/Q mismatch include:
For example, some, but not all, of the effects ofchronic obstructive pulmonary disease (COPD)are related to V/Q mismatch. You can experiencewheezing, dyspnea, and fatigue with COPD. As the disease progresses, V/Q mismatch tends to worsen too, adding to symptoms.
A lung infection likepneumoniacauses fever, chest discomfort, and fatigue—whether you have V/Q mismatch or not. If the infectionalsocauses V/Q mismatch, that can worsen fatigue.
Complications
Low oxygen concentration in the blood and tissues is problematic in the short term and in the long term, although it might not cause symptoms when oxygen levels are mildly low—especially if the process is gradual.
Lung diseases typically affect airflow and blood flow in the lungs. When disease in the lungs affects airflow and blood flow unequally, V/Q mismatch occurs.
Diseases that interfere with airflow in the bronchi or alveoli result in a decreased V/Q ratio. Diseases that obstruct pulmonary capillary blood flow result in an increased V/Q ratio.
Decreased V/Q Ratio
Lung diseases like COPD or asthma can impair airflow with little effect on pulmonary blood flow, resulting in low ventilation and nearly normal perfusion. This is described as a decreased V/Q ratio because the ventilation is more severely affected than the perfusion.
An actual object can block a bronchus, which prevents air from passing through a part of the lungs. This also results in a low V/Q ratio.
Conditions that may result in a decreased V/Q ratio include:
Increased V/Q Ratio
An increased V/Q ratio occurs when there is decreased perfusion in the lungs. Even with normal airflow or minimally impaired airflow, you could develop a V/Q mismatch in which the perfusion is low with nearly normal ventilation. This can occur due to disease or blockage of the blood vessels in the lungs.
The most common cause of a sudden increase in the V/Q ratio is a pulmonary embolism which can result from adeep vein thrombosis (DVT). This is a blood clot in the legs or arms that travels to the lungs.
It can obstruct blood flow in a pulmonary vein, decreasing perfusion to a region in the lung. Even as you inhale oxygen-rich air into your lungs, the lack of adequate blood flow means that the oxygen can’t get into your blood.
An increased V/Q ratio may also be seen with:
Mixed V/Q Ratio
Some conditions, such aslung cancer, may cause damage to the airways and/or the pulmonary blood vessels—resulting in a decreased or an increased V/Q ratio, depending on the exact location of the damage in the lungs.
And when there is extensive involvement of lung cancer, either due to primary lung cancer ormetastasis from cancer elsewhere in the body, you can have some areas of increased V/Q ratio and other areas of decreased V/Q ratio throughout the lungs.
A pulmonary ventilation/perfusion (V/Q) scan is a type of X-ray used to measure your V/Q ratio. It can effectively identify a V/Q mismatch. The test involves two simultaneous parts.
This is completely safe. Your airflow and the blood flow will be visualized and measured because the radioactive substance will show up in your lung capillaries and lung airways on the image.
Anormal V/Q ratiois around 0.80. Roughly four liters of oxygen and five liters of blood pass through the lungs per minute. A ratio aboveorbelow 0.80 is considered abnormal.Higher-than-normal results indicate reduced perfusion; lower-than-normal results indicate reduced ventilation.
Compensatory Changes
With longstanding lung disease, the alveoli and capillaries can widen or narrow in response to changes in airflow and blood flow. This is your body’s way of compensating, and these adjustments can correct a V/Q mismatch even while your lungs remain damaged.
In other words, you might have an improvement of V/Q mismatch even as your lung disease advances, but this doesn’t mean that you can stop your treatment. Your symptoms and the results of other diagnostic tests can put this all in perspective to help your healthcare provider advise next steps.
Complementary Tests
There is a high likelihood that you will also have other tests along with your V/Q scan to help identify the cause of your lung disease and your V/Q mismatch.
These other tests may include:
Since V/Q mismatch is an effect of lung disease, the treatment is focused on managing the underlying condition itself.
Treatments may include medication,oxygen supplementation, and/or surgical intervention. You will likely have your oxygen levels monitored, especially if you are being treated for an urgent condition such as pulmonary embolus and pulmonary edema.
Pulmonary Embolus
Pulmonary embolus is treated with blood thinners. Sometimes surgical embolectomy is needed to remove the blood clot.
The placement of a filter in a vein (often in the arm) may be used as a strategy to prevent recurrent pulmonary embolus.
Treatment of Pulmonary Embolus
Infection
An infection may require treatment withantibiotics. Sometimes supplemental oxygen therapy can be helpful until the infection resolves.
Asthma and COPD
Both asthma and COPD are treated with medications such ascorticosteroid inhalersandbronchodilators.Supplemental oxygen might be necessary for advanced disease.
Pulmonary Edema
Pulmonary edemais treated withdiureticsas well as supplemental oxygen.
Heart disease, pulmonary hypertension, and liver disease all are treated with a combination of medications and, in some cases, other treatments tailored to the condition.
Your V/Q ratio may improve as your condition improves. Typically, your symptoms and the results of complementary tests should improve with treatment as well.
A Word From Verywell
Often, V/Q mismatch is a sign of lung disease. A measure of your V/Q ratio is part of the diagnostic testing that is done for the evaluation of certain lung diseases, especially when there is a high suspicion of a pulmonary embolism. Your V/Q scan results are used along with the results of your other tests to help guide treatment.
8 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Baumgardner JE, Hedenstierna G.Ventilation/perfusion distributions revisited.Curr Opin Anaesthesiol. 2016;29(1):2-7. doi:10.1097/ACO.0000000000000269Petersson J, Glenny RW.Gas exchange and ventilation-perfusion relationships in the lung.Eur Respir J. 2014;44(4):1023-1041. doi:10.1183/09031936.00037014Powers KA, Dhamoon AS.Physiology, pulmonary ventilation and perfusion. StatPearls.Sarkar M, Niranjan N, Banyal PK.Mechanisms of hypoxemia[published correction appears in Lung India. 2017;34(2):220].Lung India. 2017;34(1):47–60. doi:10.4103/0970-2113.197116Bajc M, Lindqvist A.Ventilation/perfusion SPECT imaging—diagnosing other cardiopulmonary diseases beyond pulmonary embolism.Semin Nucl Med. 2019;49(1):4-10. doi:10.1053/j.semnuclmed.2018.10.012National Heart, Lung, and Blood Institute.Lung V/Q scan.Cleveland Clinic.Hypoxemia: management and treatment.American Lung Association.Managing your COPD medications.
8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Baumgardner JE, Hedenstierna G.Ventilation/perfusion distributions revisited.Curr Opin Anaesthesiol. 2016;29(1):2-7. doi:10.1097/ACO.0000000000000269Petersson J, Glenny RW.Gas exchange and ventilation-perfusion relationships in the lung.Eur Respir J. 2014;44(4):1023-1041. doi:10.1183/09031936.00037014Powers KA, Dhamoon AS.Physiology, pulmonary ventilation and perfusion. StatPearls.Sarkar M, Niranjan N, Banyal PK.Mechanisms of hypoxemia[published correction appears in Lung India. 2017;34(2):220].Lung India. 2017;34(1):47–60. doi:10.4103/0970-2113.197116Bajc M, Lindqvist A.Ventilation/perfusion SPECT imaging—diagnosing other cardiopulmonary diseases beyond pulmonary embolism.Semin Nucl Med. 2019;49(1):4-10. doi:10.1053/j.semnuclmed.2018.10.012National Heart, Lung, and Blood Institute.Lung V/Q scan.Cleveland Clinic.Hypoxemia: management and treatment.American Lung Association.Managing your COPD medications.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Baumgardner JE, Hedenstierna G.Ventilation/perfusion distributions revisited.Curr Opin Anaesthesiol. 2016;29(1):2-7. doi:10.1097/ACO.0000000000000269Petersson J, Glenny RW.Gas exchange and ventilation-perfusion relationships in the lung.Eur Respir J. 2014;44(4):1023-1041. doi:10.1183/09031936.00037014Powers KA, Dhamoon AS.Physiology, pulmonary ventilation and perfusion. StatPearls.Sarkar M, Niranjan N, Banyal PK.Mechanisms of hypoxemia[published correction appears in Lung India. 2017;34(2):220].Lung India. 2017;34(1):47–60. doi:10.4103/0970-2113.197116Bajc M, Lindqvist A.Ventilation/perfusion SPECT imaging—diagnosing other cardiopulmonary diseases beyond pulmonary embolism.Semin Nucl Med. 2019;49(1):4-10. doi:10.1053/j.semnuclmed.2018.10.012National Heart, Lung, and Blood Institute.Lung V/Q scan.Cleveland Clinic.Hypoxemia: management and treatment.American Lung Association.Managing your COPD medications.
Baumgardner JE, Hedenstierna G.Ventilation/perfusion distributions revisited.Curr Opin Anaesthesiol. 2016;29(1):2-7. doi:10.1097/ACO.0000000000000269
Petersson J, Glenny RW.Gas exchange and ventilation-perfusion relationships in the lung.Eur Respir J. 2014;44(4):1023-1041. doi:10.1183/09031936.00037014
Powers KA, Dhamoon AS.Physiology, pulmonary ventilation and perfusion. StatPearls.
Sarkar M, Niranjan N, Banyal PK.Mechanisms of hypoxemia[published correction appears in Lung India. 2017;34(2):220].Lung India. 2017;34(1):47–60. doi:10.4103/0970-2113.197116
Bajc M, Lindqvist A.Ventilation/perfusion SPECT imaging—diagnosing other cardiopulmonary diseases beyond pulmonary embolism.Semin Nucl Med. 2019;49(1):4-10. doi:10.1053/j.semnuclmed.2018.10.012
National Heart, Lung, and Blood Institute.Lung V/Q scan.
Cleveland Clinic.Hypoxemia: management and treatment.
American Lung Association.Managing your COPD medications.
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