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Ventilation/perfusion (V/Q) mismatch

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Ventilation/perfusion (V/Q) mismatch occurs when the air reaching the alveoli (ventilation) doesn't match the blood flow in the surrounding capillaries (perfusion). This imbalance can lead to inefficient gas exchange and reduced oxygen levels in the blood.

5 Must Know Facts For Your Next Test

  1. V/Q mismatch can cause hypoxemia, which is a low level of oxygen in the blood.
  2. Common causes include pulmonary embolism, chronic obstructive pulmonary disease (COPD), and pneumonia.
  3. It is diagnosed using imaging techniques such as ventilation-perfusion scans or arterial blood gas analysis.
  4. Physiological shunt and dead space are two types of V/Q mismatches; a shunt has low V/Q ratio while dead space has high V/Q ratio.
  5. Treatments may involve addressing the underlying cause, such as using medications for infections or procedures to remove blockages.

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