-
Critical care medicine · Apr 2022
The Influence of Hypercapnia and Atmospheric Pressure on the PaO2/FIO2 Ratio-Pathophysiologic Considerations, a Case Series, and Introduction of a Clinical Tool.
- Vincent J H S Gilissen, Mark V Koning, and Markus Klimek.
- Department of Intensive Care Medicine, Rijnstate Ziekenhuis, Arnhem, The Netherlands.
- Crit. Care Med. 2022 Apr 1; 50 (4): 607613607-613.
ObjectivesThe ratio between Pao2 and Fio2 is used as a marker for impaired oxygenation and acute respiratory distress syndrome classification. However, any discrepancy between Fio2 and o2 fraction in the alveolus affects the Pao2/Fio2 ratio. Correcting the Pao2/Fio2 ratios using the alveolar gas equation may result in an improved reflection of the pulmonary situation. This study investigates the difference between standard and corrected Pao2/Fio2 in magnitude, its correlation with the mortality of acute respiratory distress syndrome classification, and trends over time.DesignA register and a retrospective study combined with the development of a mathematical model to determine the difference between standard and corrected Pao2/Fio2 ratio for various levels of Paco2 and atmospheric pressure.SettingICU in a secondary hospital in The Netherlands.PatientsPatients admitted to the ICU for pneumonia or acute respiratory distress syndrome. Register cohort: January 1, 2010, till March 1, 2020 (n = 1008). Retrospective cohort: March 1, 2020, till June 1, 2020 (n = 34).Measurements And Main ResultsThe register was used to determine the 7-day ICU mortality per acute respiratory distress syndrome classification based on the standard and corrected Pao2/Fio2 ratio. The retrospective dataset correlated the Paco2 with Pao2/Fio2 ratio over time in patients with assumed stable oxygenation. The model demonstrated an increased difference between the standard and corrected Pao2/Fio2 ratios by a lower Fio2 and atmospheric pressure and higher Pao2 and Paco2. Reclassification of severe acute respiratory distress syndrome resulted in an increase in mortality from 28.1% for standard Pao2/Fio2 to 30.6% for corrected Pao2/Fio2 ratios. Acute Physiology and Chronic Health Evaluation scores correlated better with 7-day ICU-mortality when corrected Pao2/Fio2 ratio was used for classification. For patients with Fio2 less than 50% (n = 55), change in Paco2 correlated with change in Pao2/Fio2 ratio (r = -0.388; p = 0.003).InterventionsA corrected Pao2/Fio2 ratio was calculated.ConclusionsCorrecting the Pao2/Fio2 ratio for the alveolar gas equation predominantly affects patients with high ratios between Pao2 and Fio2 and Paco2 and at low atmospheric pressure. Using the corrected Pao2/Fio2 ratio for acute respiratory distress syndrome classification results in improved correlation with the 7-day ICU mortality and increases generalization among acute respiratory distress syndrome studies. The authors provide a free, web-based tool.Copyright © 2022 by the Society of Critical Care Medicine and Wolters Kluwer Health, Inc. All Rights Reserved.
Notes
Knowledge, pearl, summary or comment to share?You can also include formatting, links, images and footnotes in your notes
- Simple formatting can be added to notes, such as
*italics*
,_underline_
or**bold**
. - Superscript can be denoted by
<sup>text</sup>
and subscript<sub>text</sub>
. - Numbered or bulleted lists can be created using either numbered lines
1. 2. 3.
, hyphens-
or asterisks*
. - Links can be included with:
[my link to pubmed](http://pubmed.com)
- Images can be included with:
![alt text](https://bestmedicaljournal.com/study_graph.jpg "Image Title Text")
- For footnotes use
[^1](This is a footnote.)
inline. - Or use an inline reference
[^1]
to refer to a longer footnote elseweher in the document[^1]: This is a long footnote.
.