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2023, Number 1

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Med Crit 2023; 37 (1)

PaO2/FAO2 index: a better oxygenation indicator to assess hypoxemia? Results of an analysis of agreement with the PaO2/FiO2 index

Rojas CL, Vidal AE, Cerón DUW

Language: Spanish
References: 10
Page: 21-25
PDF size: 230.61 Kb.


ABSTRACT

Introduction: the PaO2/FiO2 ratio adjusted to barometric pressure is used to assess oxygenation in respiratory failure; however, it does not take PaCO2 into account, unlike the PaO2/FAO2 ratio (PaO2 divided by the alveolar fraction of oxygen). Objective: to evaluate the agreement between PaO2/FiO2 and PaO2/FAO2. Material and methods: observational, ambispective, cross-sectional and analytical study in patients older than 18 years, under invasive mechanical ventilation with respiratory failure and with different PaCO2 values. Results: agreement was analyzed in 64 gasometric measurements taken at admission and when the highest PaCO2 was documented, of 32 patients. The Bland and Altman analysis showed a mean of the differences (bias) of 13 and a 95% limit of agreement, between 54 and -24. Agreement is better when PaO2/FiO2 is greater than 150. Twenty two percent of the measurements did not agree in the assignment to groups with mild, moderate, or severe hypoxemia. Conclusions: there is moderate agreement between PaO2/FAO2 and PaO2/FiO2; however, in patients with severe hypoxemia, agreement is better. In patients with PaO2/FiO2 ≥ 150, hypercapnia partly explains the low agreement. PaO2/FAO2 is possibly a better way to assess the degree of oxygenation disturbance.


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