Ventilation/perfusion ratio

In respiratory physiology, the ventilation/perfusion ratio (V/Q ratio) is a ratio used to assess the efficiency and adequacy of the ventilation-perfusion coupling and thus the matching of two variables:

The V/Q ratio can therefore be defined as the ratio of the amount of air reaching the alveoli per minute to the amount of blood reaching the alveoli per minute—a ratio of volumetric flow rates. These two variables, V and Q, constitute the main determinants of the blood oxygen (O2) and carbon dioxide (CO2) concentration.

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 (ventilation scan) within the lungs.[2] V/Q scans are primarily used for the diagnosis of a blood clot in the lungs, called a pulmonary embolism.[3]

A V/Q mismatch can cause Type 1 respiratory failure.

  1. ^ Derenoncourt, Paul-Robert; Felder, Gabriel J.; Royal, Henry D.; Bhalla, Sanjeev; Lang, Jordan A.; Matesan, Manuela C.; Itani, Malak (November 2021). "Ventilation-Perfusion Scan: A Primer for Practicing Radiologists". RadioGraphics. 41 (7): 2047–2070. doi:10.1148/rg.2021210060. ISSN 0271-5333.
  2. ^ Mirza, Hasan; Hashmi, Muhammad F. (2023), "Lung Ventilation Perfusion Scan (VQ Scan)", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 33232086, retrieved 2023-11-12
  3. ^ Roach, Paul J.; Schembri, Geoffrey P.; Bailey, Dale L. (2013-09-01). "V/Q Scanning Using SPECT and SPECT/CT". Journal of Nuclear Medicine. 54 (9): 1588–1596. doi:10.2967/jnumed.113.124602. ISSN 0161-5505. PMID 23907760.