Extrapulmonary factors influencing the ratio of arterial oxygen tension to inspired oxygen concentration in burn patients

Critical Care Medicine
J A MartynJ F Burke

Abstract

The ratio of arterial oxygen tension to inspired oxygen concentration (PaO2/FIO2) as an index of respiratory function was evaluated in 22 patients with body surface area burns of 15--80%. These results indicate that this ratio is limited in its applicability because extrapulmonary factors, such as cardiac output, oxygen consumption, and arterial oxygen content, can affect this index by alterations in the amount of venous desaturation. Useful estimates of intrapulmonary right to left shunt (Qs/Qt) from PaO2/FIO2 were obtained only when arteriovenous oxygen content differences (avDO2) were between 3--5 ml/dl. There were avDO2 values above and below 3--5 ml/dl in at least 35% of the observations. Under these circumstances, PaO2/FIO2 did not correctly reflect changes in Qs/Qt. Blood gases from central venous catheters did not mirror changes in true mixed venous blood and, thus, can lead to erroneous estimations of Qs/Qt. Rational therapy of reduced arterial oxygen saturation requires measurement of both extra- and intrapulmonary factors contributing to arterial desaturation. Measurement of PaO2/FIO2 alone will not estimate these factors.

Citations

Jul 31, 1999·Archives of Medical Research·I Maulen-RadovanM Márquez Aguirre
Aug 7, 2002·Burns : Journal of the International Society for Burn Injuries·Masaru SuzukiN Aikawa
Jan 1, 1997·Critical Care Medicine·M S Gowda, R A Klocke
Jan 1, 1995·Acta Anaesthesiologica Scandinavica. Supplementum·J H Wandrup
Nov 1, 1982·Current Problems in Surgery·J V Snyder, G C Carroll
Oct 1, 1988·Acta Anaesthesiologica Scandinavica·H Zetterström
Dec 9, 2014·Anesthesiology·Edward A BittnerJ A Jeevendra Martyn
Sep 13, 2016·Critical Care Medicine·John R Feiner, Richard B Weiskopf

Related Concepts

Teens
Arteries
Burn Injury
Cardiac Output
Dioxygen
Oxygen Consumption
Pulmonary Circulation
Respiration
Mechanical Ventilation
Veins

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