@article {Chalmers1521, author = {Sarah J Chalmers and Yewande E Odeyemi and Amos Lal and Heyi Li and Ryan D Frank and Ognjen Gajic and Hemang Yadav}, title = {FIO2 Trajectory as a Pragmatic Intermediate Marker in Acute Hypoxic Respiratory Failure}, volume = {66}, number = {10}, pages = {1521--1530}, year = {2021}, doi = {10.4187/respcare.09053}, publisher = {Respiratory Care}, abstract = {BACKGROUND: Several markers of oxygenation are used as prognostic markers in acute hypoxemic respiratory failure. Real-world use is limited by the need for invasive measurements and unreliable availability in the electronic health record. A pragmatic, reliable, and accurate marker of acute hypoxemic respiratory failure is needed to facilitate epidemiologic studies, clinical trials, and shared decision-making with patients. FIO2 is easily obtained at the bedside and from the electronic health record. The FIO2 trajectory may be a valuable marker of recovery in patients with acute hypoxemic respiratory failure.METHODS: This was a historical cohort study of adult subjects admitted to an ICU with acute hypoxemic respiratory failure secondary to community-acquired pneumonia and/or ARDS.RESULTS: Our study included 2,670 subjects. FIO2 and SpO2 were consistently more available than was PaO2 in the electronic health record: (FIO2 vs SpO2 vs PaO2 : 100 vs 100 vs 72.8\% on day 1, and 100 vs 99 vs 21\% on day 5). A worsening FIO2 trajectory was associated with reduced ventilator-free days. From days 2 to 5, every increase in FIO2 by 10\% from the previous day was associated with fewer ventilator-free days (on day 2: adjusted mean {\textendash}1.25 [95\% CI {\textendash}1.45 to {\textendash}1.05] d, P \< .001). The SpO2/FIO2 trajectory also provided prognostic information. On days 3 {\textendash} 5, an increase in SpO2/FIO2 from the previous day was associated with increased ventilator-free days (on day 3: adjusted mean 2.09 (95\% CI 1.44{\textendash}2.74) d; P \< .001). SpO2/FIO2 models did not add predictive information compared with models with FIO2 alone (on day 2: adjusted FIO2 vs SpO2/FIO2 R2 0.122 vs 0.119; and on day 3: 0.153 vs 0.163).CONCLUSIONS: FIO2 and SpO2/FIO2 are pragmatic and readily available intermediate prognostic markers in acute hypoxic respiratory failure. The FIO2 trajectory in the first 5 d of ICU admission provided important prognostic information (ventilator-free days). Although the SpO2/FIO2 trajectory was also associated with ventilator-free days, it did not provide more information than the FIO2 trajectory alone.}, issn = {0020-1324}, URL = {https://rc.rcjournal.com/content/66/10/1521}, eprint = {https://rc.rcjournal.com/content/66/10/1521.full.pdf}, journal = {Respiratory Care} }