Patients with severe symptoms of COVID-19 have an ARDS. HFNC is one of the therapies to treat ARDS in COVID-19. The aim of this study is to analyse the relationship between increased D-Dimer, decreased P/F Ratio and ROX Index with failure of HFNC therapy. This study was an observational, retrospective analytic study with a total sampling technique. Ethical clearance was issued by the Ethics Committee of RSUD Dr. Soetomo Surabaya. The study was conducted in the COVID-19 isolation room from June until December 2020. The inclusion criteria were confirmed COVID-19 patients, aged 17-64 years with ARDS symptoms and requiring HFNC. D-dimer, P/F Ratio and ROX Index were observed on day 0 and day 3. The patient was followed while in COVID-19 Isolation Room-1 Dr Soetomo Hospital until discharged from isolation room or need mechanical ventilation. A total of 87 research subjects were included in this study, and 72 research subjects were further assessed on the 3rd day. The decrease in ROX Index was associated with the incidence of HFNC failure (H-0 p=0.020 and H-3 p< 0.001). The relative risk of HFNC failure in the ROX Index < 3.85 group on day 0 was 2.4 times and on day 3 was 5.1 times. The increase in D-Dimer was associated with the incidence of HFNC failure (H-0 p=0.023 and H-3 p< 0.001). The relative risk of HFNC failure in the group with D-Dimer > 1,360 mcg/l on day 0 was 2.1 times, while in the group with D-Dimer > 2,135 mcg/l on day 3 was 6.2 times. The decrease in the PF ratio was associated with the incidence of HFNC failure (H-0 p=0.011 and H-3 p< 0.001). The relative risk of HFNC failure in the group with PF ratio < 119 mmHg on day 0 was 2.3 times, while in the group with PF ratio < 110.5 mmHg on day 3 it was 9.0 times. There was a significant and strong relationship between increased D-Dimer levels, decreased PF ratio, and decreased ROX Index with the incidence of HFNC failure in the COVID-19 Isolation Room of RSUD Dr Soetomo.

D-dimer

ROX index

P/F ratio

HFNC failure

COVID-19

ARDS