Predictive Accuracy of the ROX Index for Re-Intubation in Mechanically Ventilated Patients With COVID-19

Yusuke Okazaki; Mitsuaki Nishikimi; Junki Ishii; Kohei Ota; Shinichiro Ohshimo; Nobuaki Shime

doi:10.4187/respcare.10549

Predictive Accuracy of the ROX Index for Re-Intubation in Mechanically Ventilated Patients With COVID-19

Respir Care. 2023 Aug;68(8):1067-1074. doi: 10.4187/respcare.10549. Epub 2023 May 16.

Authors

Yusuke Okazaki¹, Mitsuaki Nishikimi¹, Junki Ishii¹, Kohei Ota¹, Shinichiro Ohshimo¹, Nobuaki Shime²

Affiliations

¹ Department of Emergency and Critical Care Medicine, Graduate School of Biomedical and Health Sciences, Hiroshima University. Hiroshima, Japan.
² Department of Emergency and Critical Care Medicine, Graduate School of Biomedical and Health Sciences, Hiroshima University. Hiroshima, Japan. nshime@hiroshima-u.ac.jp.

PMID: 37193596
PMCID: PMC10353179 (available on 2024-08-01)
DOI: 10.4187/respcare.10549

Abstract

Background: Several studies have suggested that high-flow nasal cannula (HFNC) is useful for respiratory support after extubation in subjects with COVID-19 pneumonia, whereas 18% subsequently needed to undergo re-intubation. This study aimed to evaluate whether the breathing frequency (f)-ratio of oxygen saturation (ROX) index, which has been shown to be useful for predicting future intubation, is also useful for re-intubation in subjects with COVID-19.

Methods: We retrospectively analyzed mechanically ventilated subjects with COVID-19 who underwent HFNC therapy after extubation at 4 participating hospitals between January 2020-May 2022. We evaluated the predictive accuracy of ROX at 0, 1, and 2 h for re-intubation until ICU discharge and compared the area under the receiver operating characteristic (ROC) curve of the ROX index with those of f and S_pO₂ /F_IO₂ .

Results: Among the 248 subjects with COVID-19 pneumonia, 44 who underwent HFNC therapy after extubation were included. A total of 32 subjects without re-intubation were classified into the HFNC success group, and 12 with re-intubation were classified into the failure group. The overall trend that the area under the ROC curve of the ROX index was greater than that of the f and S_aO₂ /F_IO₂ was observed, although there was no statistical significance at any time point. The ROX index at 0 h, at the cutoff point of < 7.44, showed a sensitivity and specificity of 0.42 and 0.97, respectively. A trend of positive correlation between the time until re-intubation and ROX index at each time point was observed.

Conclusions: The ROX index in the early phase of HFNC therapy after extubation was useful for predicting re-intubation with high accuracy in mechanically ventilated subjects with COVID-19. Close observation for patients with < 7.44 ROX index just after extubation may be warranted because of their high risk for re-intubation.

Keywords: ROX index; SARS-CoV-2; breathing frequency; extubation; mechanical ventilation; noninvasive ventilation; re-intubation.

MeSH terms

COVID-19* / complications
COVID-19* / therapy
Cannula
Humans
Intubation, Intratracheal / adverse effects
Oxygen Inhalation Therapy / adverse effects
Respiration, Artificial / adverse effects
Respiratory Insufficiency* / therapy
Retrospective Studies