RESUMO
Background High-flow nasal cannula oxygen therapy (HFNC) is recommended for COVID-19 patients. However, the increasing use of HFNC brings a risk of delayed intubation. The optimal timing of switching from HFNC to invasive mechanical ventilation (IMV) remains unclear. An effective predictor is needed to assist in deciding on the timing of intubation. Respiratory rate and oxygenation (ROX) index, defined as (SpO2/FiO2)/respiratory rate, already show good diagnostic accuracy. Modified ROX (mROX) index, defined as (PaO2/FiO2)/respiratory rate, might be better than the ROX index in predicting HFNC failure. Objective The aim was to evaluate the predictive value of mROX for HFNC failure in COVID-19 patients. Methods Severe or critical COVID-19 patients treated with HFNC were enrolled in two clinical centers. Laboratory indicators, respiratory parameters, and mROX index at 0 h and 2 h after initial HFNC were collected. Based on the need of IMV after HFNC initiation, the patients were divided into the HFNC failure group and the HFNC success group. The predictive value of mROX index for IMV was evaluated by the area under the receiver operating characteristic curve (AUROC) and logistic regression analysis. We performed Kaplan–Meier survival analysis using the log-rank test. Results Sixty COVID-19 patients (mean age, 62.8 ± 14.1 years;42 males) receiving HFNC were evaluated, including 18 critical and 42 severe cases. A total of 33 patients had hypertension;14 had diabetes;17 had chronic cardiac disease;11 had chronic lung disease;13 had chronic kidney disease;and 17 had a history of stroke. The AUROC of mROX index at 2 h was superior than that of other respiratory parameters to predict the need of IMV (0.959;P < 0.001). At the mROX index cutoff point of 4.45, predicting HFNC failure reached the optimal threshold, with specificity of 94% and sensitivity of 92%. Logistic regression analysis showed that 2-h mROX index below 4.45 was a protective factor for IMV (OR 0.18;95% CI, 0.05 to 0.64;P = 0.008). In the HFNC failure group, the median time from HFNC to IMV was 22.5 h. The 28-day mortality of the late intubation patients (≥22.5 h) was higher than that of the early intubation patients (<22.5 h) (53.8% vs 8.3%, P = 0.023). Conclusion mROX at 2 h is a good early warning index for the need of IMV in COVID-19 patients after HFNC initiation. Early intubation may lead to better survival in patients with 2-h mROX index below 4.45.
RESUMO
BACKGROUND: This study was designed to explore the early predictive value of the respiratory rate oxygenation (ROX) index modified by PaO2 (mROX) in high-flow nasal cannula (HFNC) therapy in patients with acute hypoxemia respiratory failure (AHRF). METHOD: Seventy-five patients with AHRF treated with HFNC were retrospectively reviewed. Respiratory parameters at baseline and 2 h after HFNC initiation were analyzed. The predictive value of the ROX (ratio of pulse oximetry/FIO2 to respiratory rate) and mROX (ratio of arterial oxygen /FIO2 to respiratory rate) indices with two variations by adding heart rate to each index (ROX-HR and mROX-HR) was evaluated. RESULTS: HFNC therapy failed in 24 patients, who had significantly higher intensive care unit (ICU) mortality and longer ICU stay. Both the ROX and mROX indices at 2 h after HFNC initiation can predict the risk of intubation after HFNC. Two hours after HFNC initiation, the mROX index had a higher area under the receiver operating characteristic curve (AUROC) for predicting HFNC success than the ROX index. Besides, baseline mROX index of greater than 7.1 showed a specificity of 100% for HFNC success. CONCLUSION: The mROX index may be a suitable predictor of HFNC therapy outcomes at the early phase in patients with AHRF.