This study examined the use of the mP-ROX index and ROX index as predictors of HFNC failure performed in patients aged 1 month to 18 years who received HFNC therapy with various etiologies. This study found that the ROX index is a parameter that can be used to assess HFNC failure in children, apart from clinical assessment. In Table 1, there are no differences in general characteristics between the two groups. However, there was a significant difference in the duration of HFNC use, whereas in the successful group, the duration of HFNC use was found to be longer. The duration of HFNC use was also significantly longer in the successful group in a study on bronchiolitis in infants.11–13 This is due to switching to mechanical ventilation therapy in failed groups, which was associated with a longer length of stay.14,15
There was no significant difference in blood gas analysis (BGA) results at 60 minutes between both groups. This shows that BGA examination does not always correlate with the patient's clinical condition. Routine sampling in the evaluation of HFNC therapy is also less effective and increases parental anxiety, child pain, and costs.
The severity of disease was assessed with S/F ratio, mP-ROX index, and ROX index was not found to be significantly different in the two groups (Table 2). The S/F ratio is a valuable and easy tool to assess the severity of respiratory distress. There was no difference in the initial HFNC settings, and there was no difference in the severity of respiratory distress. Lemiale et al. suggested that the ROX index can be used as a risk stratification for intubation to differentiate patients who would likely fail HFNC therapy.16
Assessment with the mP-ROX index at 60 and 90 minutes did not show a significant difference between the two groups. However, there was a significant difference in the assessment with the ROX index in the success and failure groups (p < 0.05). It can be concluded that the ROX index is more reliable in assessing failure of HFNC therapy. As far as this research is concerned, there are only two studies regarding the P-ROX index as a predictor of HFNC therapy failure in the pediatric population. Yildizdas et al. used the respiratory rate z-score compared to the patient's respiratory rate and found a P-ROX index above 66.7 at the 24th hour as the cut-off value.5 Saelim et al. found that the P-ROX index could be a helpful predictor in assessing failure of HFNC therapy using age-associated respiratory rate.12 However, Kim et al. suggested that using the median RR rather than the respiratory z-score in the P-ROX index showed a better diagnostic value in pediatric patients with hypoxic respiratory failure.17
Table 3 showed that there was no correlation between the initial mP-ROX and ROX index, but a moderate correlation was found at 60 and 90 minutes. This indicates that the mP-ROX index has not proven useful in determining HFNC failure in children. In contrast to research by Yildizdas et al. which states that the P-ROX index can be used as a good predictor for failure of HFNC therapy in the pediatric population.5 However, this study used the respiratory rate percentile based on the Fleming chart to calculate the mP-ROX index rather than the respiratory z-score.
Based on Table 4, we created an HFNC management chart for clinicians to determine the failure of HFNC therapy in children (Fig. 3). This study evaluated the ROX index at several time points: initial, 60th minute, 90th, and 24th hour. It was found that the 60th-minute ROX index with a cutoff value < 5.52 (AUC 0.785) had a sensitivity of 0.9 and a specificity of 0.708. The 90th-minute ROX index with a cut point < 5.68 (AUC 0.797) had a sensitivity of 0.78 and a specificity of 0.758. This shows that the ROX index is a good predictive factor for HFNC therapy in pediatric patients. In this study, after 24 hours of initiation of HFNC use, no HFNC failure was found, with a duration of HFNC use of 4 (1–27) days. This is supported by several studies that suggest that failure generally occurs 5 to 12 hours after initiation of HFNC therapy. This illustrates the importance of constant monitoring during HFNC therapy to prevent clinical deterioration.11,18
In this study, PICU length of stay was shorter in the failure group than in the success group. The shorter duration can be due to the severity of the disease, causing death cases. Meanwhile, the length of stay at the hospital was found to be longer in the failure group due to the use of mechanical ventilation. This was supported by Kannikeswaran et al. and Nascimento et al. who found that the duration of hospitalization was longer in the group that received positive pressure ventilation or in the group that failed HFNC.11,13