The mechanisms of abnormal gas exchange in acute massive pulmonary embolism

Am Rev Respir Dis. 1983 Jul;128(1):170-2. doi: 10.1164/arrd.1983.128.1.170.


Hypoxemia usually accompanies acute pulmonary embolism in humans, but its mechanism remains poorly understood. We studied 2 patients with acute, massive pulmonary embolism (APE) documented by pulmonary angiography. Both patients had a markedly increased alveolar-arterial oxygen difference (AaPO2). The technique of multiple inert gas elimination was used to determine the distribution of ventilation-perfusion ratios (VA/Q). An increase in VA/Q inequality was found in both patients, but this increased inequality was caused entirely by an increase in the ventilation of lung units with high VA/Q ratio. No blood flow was found perfusing lung units with a VA/Q ratio of less than 1.0. Both patients, however, had a large amount of blood flow (20 and 39% of the cardiac output) perfusing unventilated lung units (shunt), and the percent of minute ventilation to unperfused lung units as well as the VD/VT determined from the Bohr equation were increased. We conclude that in these 2 patients with APE, VA/Q inequality did not play a major role in their hypoxemia and that the widened AaPO2 is explained by the large shunts that were found.

Publication types

  • Case Reports

MeSH terms

  • Acute Disease
  • Aged
  • Female
  • Hemodynamics
  • Humans
  • Hypoxia / physiopathology
  • Partial Pressure
  • Pulmonary Embolism / physiopathology*
  • Pulmonary Gas Exchange*
  • Ventilation-Perfusion Ratio