Effectiveness of the use of a high-flow nasal cannula to treat COVID-19 patients and risk factors for failure: a meta-analysis

Background: Coronavirus disease 2019 (COVID-19) has spread globally, and many patients with severe cases have received oxygen therapy through a high-flow nasal cannula (HFNC). Objectives: We assessed the efficacy of HFNC for treating patients with COVID-19 and risk factors for HFNC failure. Methods: We searched PubMed, Embase, and the Cochrane Central Register of randomized controlled trials (RCTs) and observational studies of HFNC in patients with COVID-19 published in English from January 1st, 2020 to August 15th, 2021. The primary aim was to assess intubation, mortality, and failure rates in COVID-19 patients supported by HFNC. Secondary aims were to compare HFNC success and failure groups and to describe the risk factors for HFNC failure. Results: A total of 25 studies fulfilled selection criteria and included 2851 patients. The intubation, mortality, and failure rates were 0.44 (95% confidence interval (CI): 0.38-0.51, I-2 = 84%), 0.23 (95% CI: 0.19-0.29, I-2 = 88%), and 0.47 (95% CI: 0.42-0.51, I-2 = 56%), respectively. Compared to the success group, age, body mass index (BMI), Sequential Organ Failure Assessment (SOFA) score, Acute Physiology and Chronic Health Evaluation (APACHE) II score, D-dimer, lactate, heart rate, and respiratory rate were higher and PaO2, PaO2/FiO(2), ROX index (the ratio of SpO(2)/FiO(2) to respiratory rate), ROX index after the initiation of HFNC, and duration of HFNC were lower in the failure group (all Ps < 0.05). There were also more smokers and more comorbidities in the failure group (all Ps < 0.05). Pooled odds ratios (ORs) revealed that older age (OR: 1.04, 95% CI: 1.01-1.07, P = 0.02, I-2 = 88%), a higher white blood cell (WBC) count (OR: 1.06, 95% CI: 1.01-1.12, P = 0.02, I-2 = 0%), a higher heart rate (OR: 1.42, 95% CI: 1.15-1.76, P < 0.01, I-2 = 0%), and a lower ROX index(OR: 0.61, 95% CI: 0.39-0.95, P = 0.03, I-2 = 93%) after the initiation of HFNC were all significant risk factors for HFNC failure. Conclusions: HFNC is an effective way of providing respiratory support in the treatment of COVID-19 patients. Older age, a higher WBC count, a higher heart rate, and a lower ROX index after the initiation of HFNC are associated with an increased risk of HFNC failure.