Change in Pulmonary Venous Admixture With Varying Inspired Oxygen

Anesth Analg. Sep-Oct 1976;55(5):688-95. doi: 10.1213/00000539-197609000-00016.


Pulmonary venous admixture (Qsp/Qt) was analyzed as a function of fractional concentration of inspired O2 (FIO2) in 30 patients who required postoperative mechanical ventilation. Pulmonary and radial artery blood-gas tensions and pH were measured and Qsp/Qt was calculated with FIO2 ranging from 0.21 to 1. In all patients, Qsp/Qt decreased when FIO2 was increased from 0.21 to 0.4 and then stabilized to an FIO2 of approximately 0.6. As the FIO2 was increased to 1, Qsp/Qt increased. Since the inhalation of gas mixture with FIO2 greater than or equal to 0.6 increased right-to-left intrapulmonary shunting of blood, we recommend respiratory function be evaluated during inhalation of a clinically useful concentration of O2 rather than at an FIO2 of 1.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Humans
  • Oxygen / blood*
  • Postoperative Care
  • Respiration, Artificial*
  • Ventilation-Perfusion Ratio*


  • Oxygen