Reliability of the respiratory rate and oxygenation index for successful high-flow nasal cannula support in coronavirus disease pneumonia: a retrospective cohort study

Ryosuke Hirabayashi; Kazuma Nagata; Yuki Sato; Atsushi Nakagawa; Ryo Tachikawa; Hirokazu Kuroda; Ryutaro Seo; Takeshi Morimoto; Keisuke Tomii

doi:10.1186/s12890-023-02598-y

Reliability of the respiratory rate and oxygenation index for successful high-flow nasal cannula support in coronavirus disease pneumonia: a retrospective cohort study

BMC Pulm Med. 2023 Aug 10;23(1):294. doi: 10.1186/s12890-023-02598-y.

Authors

Ryosuke Hirabayashi¹, Kazuma Nagata², Yuki Sato², Atsushi Nakagawa², Ryo Tachikawa², Hirokazu Kuroda³, Ryutaro Seo⁴, Takeshi Morimoto^{5

6}, Keisuke Tomii²

Affiliations

¹ Department of Respiratory Medicine, Kobe City Medical Center General Hospital, 2-1-1 Minatojima-Minamimachi, Chuo-Ku, Kobe, Hyogo, 650-0047, Japan. rhirabayashi0405@kcho.jp.
² Department of Respiratory Medicine, Kobe City Medical Center General Hospital, 2-1-1 Minatojima-Minamimachi, Chuo-Ku, Kobe, Hyogo, 650-0047, Japan.
³ Department of Infectious Disease, Kobe City Medical Center General Hospital, Kobe, Hyogo, Japan.
⁴ Department of Emergency Medicine, Kobe City Medical Center General Hospital, Kobe, Hyogo, Japan.
⁵ Department of Clinical Epidemiology, Hyogo Medical University, Nishinomiya, Hyogo, Japan.
⁶ Department of Clinical Research Center, Kobe City Medical Center General Hospital, Kobe, Hyogo, Japan.

Abstract

Background: High-flow nasal cannula (HFNC) therapy is an important non-invasive respiratory support in acute respiratory failure, including coronavirus disease (COVID-19) pneumonia. Although the respiratory rate and oxygenation (ROX) index is a simple and useful predictor for HFNC failure and mortality, there is limited evidence for its use in patients with COVID-19 pneumonia. We aimed to evaluate the ROX index as a predictor for HFNC failure in patients with COVID-19 pneumonia. We also evaluated the ROX index as a predictor for 28-day mortality.

Methods: In this single-center, retrospective, cohort study, 248 patients older than 18 years of age with COVID-19 pneumonia received HFNC therapy for acute respiratory failure. The ROX index was evaluated within 4 h from the start of HFNC therapy. Past medical history, laboratory data, and the ROX index were evaluated as predictors for HFNC failure and 28-day mortality.

Results: The ROX index < 4.88 showed a significantly high risk ratio for HFNC failure (2.13 [95% confidence interval [CI]: 1.47 - 3.08], p < 0.001). The ROX index < 4.88 was significantly associated with 28-day mortality (p = 0.049) in patients with COVID-19 pneumonia receiving HFNC therapy. Age, chronic hypertension, high lactate dehydrogenase level, and low ROX index showed significantly high risk ratio for HFNC failure. C-reactive protein level and low ROX index were predictors of 28-day morality.

Conclusion: The ROX index is a useful predictor for HFNC success and 28-day mortality in patients with COVID-19 pneumonia receiving HFNC therapy.

Trial registration: An independent ethics committee approved the study (Research Ethics Review Committee of Kobe City Medical Center General Hospital [number: zn220303; date: February 21, 2022]), which was performed in accordance with the Declaration of Helsinki, Guidelines for Good Clinical Practice.

Keywords: COVID-19; High-flow nasal cannula; Pneumonia; ROX index; Respiratory failure; S/F ratio.

MeSH terms

COVID-19* / therapy
Cannula
Cohort Studies
Humans
Noninvasive Ventilation*
Oxygen Inhalation Therapy
Reproducibility of Results
Respiratory Distress Syndrome*
Respiratory Insufficiency* / therapy
Respiratory Rate
Retrospective Studies