A clinical comparison of indices of pulmonary gas exchange with changes in the inspired oxygen concentration

Canadian Journal of Anaesthesia = Journal Canadien D'anesthésie
I A HerrickA B Froese

Abstract

Several indices have been introduced as convenient alternatives to calculation of the physiological shunt fraction (Qs/QT) for the assessment of pulmonary gas exchange. These include: the arterial-alveolar oxygen tension ratio (a/APO2), the arterial oxygen tension-inspired oxygen concentration ratio (PaO2/FIO2), the respiratory index (RI), [A-a)DO2/PaO2) and the alveolar-arterial oxygen tension difference [A-a)Do2). These indices are in use clinically despite the fact that they may not accurately predict gas exchange in situations where FIO2, Qs/QT or arterial-venous oxygen content is changing. The clinical stability of each of these indices, relative to the behaviour of the physiological shunt, was therefore investigated prospectively in ten mechanically ventilated postoperative adults as FIO2 was varied from 0.30 to 1.00. None of the indices studied reliably reflected the behaviour of the physiological shunt. As FIO2 was increased incrementally from 0.30 to 1.00, 42 to 55 per cent of the measured changes in these indices were opposite in direction to the corresponding changes in the physiological shunt. The maximum magnitudes of the opposite changes were substantial; 24 and 22 per cent for the a/APO2 and PaO2/FIO2 ratio respe...Continue Reading

References

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Citations

Apr 1, 1991·Canadian Journal of Anaesthesia = Journal Canadien D'anesthésie·W A Tweed, T L Lee
Nov 1, 1991·Canadian Journal of Anaesthesia = Journal Canadien D'anesthésie·W A TweedT L Lee
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Aug 24, 2019·Pediatric Nephrology : Journal of the International Pediatric Nephrology Association·Alexandra IdrovoLeyat Tal
Aug 4, 2015·Critical Care Medicine·Katlynd M ŠunjićStacey L Folse
Dec 1, 1993·Anaesthesia and Intensive Care·W A TweedT L Lee
Jan 8, 2015·The New England Journal of Medicine·Aaron Spital
Jan 8, 2015·The New England Journal of Medicine·Mohamed A ShetaPaul Drawz

Related Concepts

Pulmonary Gas Exchange
Respiration
Mechanical Ventilation
Weight

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