Abstract
Using high-flow nasal cannula (HFNC) in patients with hypoxemic respiratory failure to avoid intubation raises concerns about its potential to increase mortality due to delayed intubation. Identifying at-risk patients is essential. While the literature predicts risk with oxygen-based indices (ROX, SpO2/FiO2, PaO2/FiO2), we aimed to detect ventilation insufficiency. To achieve this, we developed a simplified and modified "ventilatory ratio" (VRm), assessed its predictive value, and compared it with the ROX index. In this retrospective, observational study, patients in the intensive care unit who received high-flow nasal cannula therapy were divided into 2 groups: a failure group, consisting of those who underwent intubation, and a success group. After excluding metabolic and organic disorders that could affect ventilation (such as chronic obstructive pulmonary disease, obesity hypoventilation, renal failure, and sepsis), data from 15 patients (7 non-intubated, 8 intubated) were analyzed. There were no significant differences between the 2 groups in terms of age, Apache II score, length of stay in the intensive care unit, arterial blood gas values, SpO2/FiO2 or PaO2/FiO2. The ROX index and VRm values were significantly different in both groups. The diagnostic accuracy (area under the ROC curve - AUC) of the ROX index for predicting the need for intubation was significantly high, at 0.89 (95% CI: 0.63-0.99; P < .001). The optimal cutoff value for the ROX index was ≤ 3.92. The VRm index demonstrated a diagnostic accuracy of AUC = 0.93 (95% CI: 0.67-1) and was also significantly high (P < .001). The optimal cutoff value for VRm was determined to be >2.68. Comparison of ROC curves between the ROX and VRm indices was not statistically significant (z = 0.41; P = .685). The VRm index may serve as a useful additional bedside tool for predicting HFNC therapy failure in hypoxemic pneumonia patients, especially in the gray zone of the ROX index.