Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Observational Study
. 2021 Oct:92:48-54.
doi: 10.1016/j.ejim.2021.06.002. Epub 2021 Jun 17.

Standardizing PaO2 for PaCO2 in P/F ratio predicts in-hospital mortality in acute respiratory failure due to Covid-19: A pilot prospective study

Irene Prediletto  1 , Letizia D'Antoni  2 , Paolo Carbonara  1 , Federico Daniele  1 , Roberto Dongilli  3 , Roberto Flore  2 , Angela Maria Grazia Pacilli  1 , Lara Pisani  1 , Corina Tomsa  2 , María Laura Vega  4 , Vito Marco Ranieri  5 , Stefano Nava  6 , Paolo Palange  2
Affiliations
Observational Study

Standardizing PaO2 for PaCO2 in P/F ratio predicts in-hospital mortality in acute respiratory failure due to Covid-19: A pilot prospective study

Irene Prediletto et al. Eur J Intern Med. 2021 Oct.

Abstract

Introduction: Up to fifteen percent of patients with novel pandemic coronavirus disease (Covid-19) have acute respiratory failure (ARF). Ratio between arterial partial pressure of oxygen (PaO2) and fraction of inspired oxygen (FiO2), P/F, is currently used as a marker of ARF severity in Covid-19. P/F does not reflect the respiratory efforts made by patients to maintain arterial blood oxygenation, such as tachypnea and hyperpnea, leading to hypocapnia. Standard PaO2, the value of PaO2 adjusted for arterial partial pressure of carbon dioxide (PaCO2) of the subject, better reflects the pathophysiology of hypoxemic ARF. We hypothesized that the ratio between standard PaO2 over FiO2 (STP/F) better predicts Covid-19 ARF severity compared to P/F.

Methods: Aim of this pilot prospectic observational study was to observe differences between STP/F and P/F in predicting outcome failure, defined as need of invasive mechanical ventilation and/or deaths in Covid-19 ARF. Accuracy was calculated using Receiver Operating Characteristics (ROC) analysis and areas under the ROC curve (AUROC) were compared.

Results: 349 consecutive subjects admitted to our respiratory wards due to Covid-19 ARF were enrolled. STP/F was accurate to predict mortality and superior to P/F with, respectively, AUROC 0.710 versus 0.688, p = 0.012.Both STP/F and PF were accurate to predict outcome failure (AUROC respectively of 0.747 and 0.742, p = 0.590).

Discussion: This is the first study assessing the role of STP/F in describing severity of ARF in Covid-19. According to results, STP/F is accurate and superior to P/F in predicting in-hospital mortality.

Keywords: Acute respiratory failure; Covid-19; Hypocapnia; PaO2/FiO2; Prognosis; Standard PaO2.

PubMed Disclaimer

Conflict of interest statement

All Authors declare no conflict of interests.

Figures

Fig 1
Fig. 1
Predictive receiver-operating characteristic (ROC) curve of the study population by outcome failure (A) and deaths (B) for STP/F and P/F.
See this image and copyright information in PMC

Comment in

References

    1. World health organization (WHO) Coronavirus Disease (COVID-19); https://covid19.who.int. Date last updated: March 31 2021. Date last accessed: March 31 2021.
    1. Stawicki S.P., Jeanmonod R., Miller A.C., Paladino L., Gaieski D.F., Yaffee A.Q., et al. The 2019-2020 Novel Coronavirus (Severe Acute Respiratory Syndrome Coronavirus 2) Pandemic: a Joint American College of Academic International Medicine-World Academic Council of Emergency Medicine Multidisciplinary COVID-19 Working Group Consensus Paper. J Glob Infect Dis. 2020;12(2):47–93. - PMC - PubMed
    1. Grasselli G., Tonetti T., Protti A., Langer T., Girardis M., Bellani G., et al. Pathophysiology of COVID-19-associated acute respiratory distress syndrome: a multicentre prospective observational study. Lancet Respir Med. 2020;8(12):1201–1208. - PMC - PubMed
    1. Li L.Q., Huang T., Wang Y.Q., Wang Z.P., Liang Y., Huang T.B., et al. COVID-19 patients' clinical characteristics, discharge rate, and fatality rate of meta-analysis. J Med Virol. 2020;92(6):577–583. - PMC - PubMed
    1. ARDS Definition Task Force. Ranieri V.M., Rubenfeld G.D., Thompson B.T., Ferguson N.D., Caldwell E., Fan E., et al. Acute respiratory distress syndrome: the Berlin Definition. JAMA. 2012;307(23):2526–2533. - PubMed

Publication types