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This matching may be assessed in the lung as a whole, or in individual or in sub-groups of gas-exchanging units in the lung. On the other side Ventilation-perfusion mismatch is the term used when the ventilation and the perfusion of a gas exchanging unit are not matched. The actual values in the lung vary depending on the position within the lung.
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.
In a condition such as pulmonary embolism, the pulmonary blood flow is affected, thus the ventilation of the lung is adequate, however there is a perfusion defect.Gas exchange thus becomes highly inefficient leading to hypoxemia, as measured by arterial oxygenation.
The lung structure is important for the mechanism of ventilation-perfusion coupling. Pleura (plural: pleurae) is a single membrane surrounding the lung. It folds back to form two layers, and each layer is called parietal pleura and visceral pleura.
Radius matching: all matches within a particular radius are used -- and reused between treatment units. Kernel matching: same as radius matching, except control observations are weighted as a function of the distance between the treatment observation's propesnity score and control match propensity score. One example is the Epanechnikov kernel.
The lattice of stable matchings is based on the following weaker structure, a partially ordered set whose elements are the stable matchings. Define a comparison operation on the stable matchings, where if and only if all doctors prefer matching to matching : either they have the same assigned hospital in both matchings, or they are assigned a better hospital in than they are in .
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Vector quantization (VQ) is a classical quantization technique from signal processing that allows the modeling of probability density functions by the distribution of prototype vectors. Developed in the early 1980s by Robert M. Gray , it was originally used for data compression .