Analysis of early predictive factors for invalidity of high flow nasal catheter oxygen therapy

Objective High-flow nasal cannula (HFNC) is a new method to treat adult respiratory distress. This study aims to explore the early predictors of the inefficiency of HFNC in patients with respiratory distress. Methods A total of 162 patients with respiratory distress were treated with HFNC oxygen therapy in the Department of Respiratory and Critical Care Medicine, Emergency and Critical Care Medicine. The age, sex, weight, history, diagnosis, vital signs, blood oxygen saturation/inhaled oxygen concentration (SpO2/FiO2, SF) ratio, and modified respiratory distress score (mRDAI) , duration of HFNC oxygen therapy, replacement of advanced oxygen therapy support time, adverse reactions and other data were extracted from the medical electronic medical records. Results A total of 154 valid samples were included, with a median age of 55 (inter-quartile range 47-72), including 59 patients (38.3%) with acute bronchiolitis, 64 patients (41.6%) with bacterial pneumonia, 31 patients (20.1%) with atypical or viral pneumonia; 129 patients (83.8%) with effective HFNC oxygen therapy and 25 patients (16.2%) with ineffective HFNC oxygen therapy. SF ratio in ineffective HFNC oxygen therapy patients at admission was lower, pH value was lower, partial pressure of carbon dioxide was higher (P values were 0.008, 0.012, 0.001). RR, mRDAI score and SF ratio in the first hour of effective HFNC oxygen therapy patients improved significantly (t values were 1.732, 9.783, 37.591, P<0.05 or 0.01). SF ratio in the first hour of HFNC was lower than 195 (area under curve 0.842, 95%CI 0.743-0.942, P<0.01). It was the critical value for the ineffectiveness of oxygen therapy. Conclusions When patients with respiratory distress are supported by HFNC oxygen therapy, the lower initial fingertip oxygen saturation, higher blood gas arterial partial pressure of carbon dioxide and lower SF ratio are the early predictors of failure of HFNC oxygen therapy. Key words: Respiratory distress; High flow oxygen therapy; Blood oxygen saturation/inhaled oxygen concentration ratio; Predictors