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Any deviation from this value is considered a V/Q mismatch. Maintenance of the V/Q ratio is crucial for preservation of effective pulmonary gas exchange and maintenance of oxygenation levels. A mismatch can contribute to hypoxemia and often signifies the presence or worsening of an underlying pulmonary condition. [3]
The V/Q ratio can be measured with a two-part ventilation/perfusion scan (V/Q scan). [1] Using a small amount of inhaled or injected radioactive material called a tracer for visualization, a V/Q scan is a type of nuclear medical imaging that allows for localization and characterization of blood flow ( perfusion scan ) and measurement of airflow ...
A pulmonary ventilation-perfusion scan (lung V/Q scan) can be used to diagnose the V/Q mismatch. A ventilation scan is used to measure airflow spread and a perfusion scan for blood flow distribution in the lungs. A radioactive tracer is used to scan the whole lung and the ventilation and perfusion function. [21]
Ventilation perfusion mismatch (V/Q mismatch), which can be either low or high. [8] A reduced V/Q ratio can be caused by impaired ventilation, which may be a consequence of conditions such as bronchitis, obstructive airway disease, mucus plugs, or pulmonary edema, which limit or obstruct the ventilation.
A pulmonary shunt is the passage of deoxygenated blood from the right side of the heart to the left without participation in gas exchange in the pulmonary capillaries. It is a pathological condition that results when the alveoli of parts of the lungs are perfused with blood as normal, but ventilation (the supply of air) fails to supply the perfused region.
A ventilation/perfusion lung scan, also called a V/Q lung scan, or ventilation/perfusion scintigraphy, is a type of medical imaging using scintigraphy and medical isotopes to evaluate the circulation of air and blood within a patient's lungs, [1] [2] in order to determine the ventilation/perfusion ratio.
Hypoxic pulmonary vasoconstriction (HPV), also known as the Euler–Liljestrand mechanism, is a physiological phenomenon in which small pulmonary arteries constrict in the presence of alveolar hypoxia (low oxygen levels).
An abnormally increased A–a gradient suggests a defect in diffusion, V/Q mismatch, or right-to-left shunt. [5] The A-a gradient has clinical utility in patients with hypoxemia of undetermined etiology. The A-a gradient can be broken down categorically as either elevated or normal. Causes of hypoxemia will fall into either category.