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The pathophysiologic mechanisms that account for the hypoxemia observed in a wide variety of diseases are ventilation-perfusion (V/Q) mismatch and shunt.
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emedicine.medscape.com/article/167981-overview
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Keywords: hypoxia, shunt, V/Q mismatch, ventilation ... Figure 3: Depression of arterial PO2 by shunting when the alveolar PO2 is raised. The addition of a small amount of shunted blood lowers the arterial oxygen content and this greatly reduces the arterial PO2 because the curve is flat at this top end.
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www.rcsed.ac.uk/Journal/vol45_4/4540007.htm
www.rcsed.ac.uk/Journal/vol45_4/4540007.htm
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These are termed V/Q MISMATCH and SHUNT. Lets see which applies to our case ... Can we convert shunt to V/Q mismatch? If so, how? ...
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medschool.slu.edu/pharmphys/respiratory_physiology_2.pd...
medschool.slu.edu/pharmphys/respiratory_physiology_2.pdf
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At the extremes of V/Q mismatch, an area of lung receiving no perfusion will have a V/Q ratio of (infinity) and is referred to as alveolar dead-space, which together with the anatomical dead-space makes up the physiological dead-space.
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www.nda.ox.ac.uk/wfsa/html/u12/u1211_02.htm
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V/Q mismatch. SHUNT. V/Q = 0. DEAD SPACE. V/Q = ∞. Atelectasis ... Pulmonary contusion. Hypoxemic Respiratory Failure. V/Q mismatch. SHUNT. V/Q = 0 ...
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scalpel.stanford.edu/ICU/presentations/Acute%20Resp%20F...
scalpel.stanford.edu/ICU/presentations/Acute%20Resp%20Failure.ppt
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In veterinary patients, diffusion impairment is rarely severe enough to cause hypoxemia in and of itself. Response to oxygen supplementation usually allows differentiation between V/Q mismatch and shunting.
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www.cvmbs.colostate.edu/clinsci/wing/trauma/dyspnea.htm
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Prevention: Never force elbow extension after the administration of muscle relaxants and careful insertion of I.V. into antecubital space. ... This results in a perfusion-ventilation mismatch.
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www.pitt.edu/~position/complications.htm
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V/Q scans detect areas of lung that are ventilated but not perfused, as occurs in PE; results are reported as low, intermediate, or high probability of PE based on patterns of V/Q mismatch. A completely normal scan excludes PE with nearly 100% accuracy, but a low-probability scan still carries a 15% likelihood of PE.
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www.merck.com/mmpe/sec05/ch050/ch050a.html
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Right-to-left shunting is an extreme example of V/Q mismatch. With shunting, deoxygenated pulmonary arterial blood arrives at the left side of the heart without having passed through ventilated lung segments.
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www.merck.com/mmpe/sec05/ch046/ch046c.html
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