Predictors of success of high-flow nasal cannula in the treatment of acute hypoxemic respiratory failure

Abstract

BackgroundHigh-flow nasal cannula (HFNC) therapy is used in the treatment of acute respiratory failure (ARF), and is both safe and effective in reversing hypoxemia. In order to minimize mortality and clinical complications associated to this practice, a series of tools must be developed to allow early detection of failure. The present study was carried out to: (a) examine the impact of respiratory rate (RR), peripheral oxygen saturation (SpO2), ROX index (ROXI = [SpO2/FiO2]/RR) and oxygen inspired fraction (FiO2) on the success of HFNC in patients with hypoxemic ARF; and (b) analyze the length of stay and mortality in the ICU, and the need for mechanical ventilation (MV). MethodsA retrospective study was carried out in the medical-surgical ICU of Hospital de Montilla (Córdoba, Spain). Patients diagnosed with hypoxemic ARF and treated with HFNC from January 2016 to January 2018 were included. ResultsOut of 27 patients diagnosed with ARF, 19 (70.37%) had hypoxemic ARF. Fifteen of them (78.95%) responded satisfactorily to HFNC, while four (21.05%) failed. After two hours of treatment, RR proved to be the best predictor of success (area under the ROC curve [AUROC] 0.858; 95%CI 0.63–1.05; p=0.035). For this parameter, the optimal cutoff point was 29rpm (sensitivity 75%, specificity 87%). After 8h of treatment, FiO2 and ROXI were reliable predictors of success (FiO2: AUROC 0.95; 95%CI 0.85–1.04; p=0.007 and ROXI: AUROC 0.967; 95%CI 0.886–1.047; p=0.005). In the case of FiO2 the optimal cutoff point was 0.59 (sensitivity 75%, specificity 93%), while the best cutoff point for ROXI was 5.98 (sensitivity 100%, specificity 75%). Using a Cox regression model, we found RR<29rpm after two hours of treatment, and FiO2<0.59 and ROXI>5.98 after 8h of treatment, to be associated with a lesser risk of MV (RR: HR 0.103; 95%CI 0.11−0.99; p=0.05; FiO2: HR 0.053; 95%CI 0.005−0.52; p=0.012; and ROXI: HR 0.077; 95%CI 0.008−0.755; p=0.028, respectively). ConclusionsRR after two hours of treatment, and FiO2 and ROXI after 8h of treatment, were the best predictors of success of HFNC. RR<29rpm, FiO2<0.59 and ROXI>5.98 were associated with a lesser risk of MV.