PI Ratio May Predict Pediatric Intubation Timing

The observational study, published in October 2026, involved 172 children aged four to ten years who underwent daytime surgery. The primary objective was to explore the value of the standardized PI ratio, defined as the postinduction PI divided by the baseline PI, as a new tool to assist clinical decision-making regarding the timing of intubation.

The study was motivated by the current reliance on clinical experience to determine the suitable timing for endotracheal intubation, a process complicated by the lack of objective and accessible indices. While the perfusion index is known to correlate with anaesthetic depth, its marked baseline variability among individuals limits its reliability as a standalone predictor. By calculating a ratio that accounts for individual baseline values, the researchers aimed to mitigate this variability and improve the predictive accuracy for haemodynamic stability during the intubation procedure.

The observational study recorded the perfusion index at three specific time points: before anaesthesia induction (T1), immediately before intubation (T2), and one minute after intubation (T3). The PI ratio was calculated by dividing the PI at T2 by the PI at T1. Children were subsequently assigned to one of two groups based on their haemodynamic response: the significant haemodynamic fluctuation (SHF) group or the non-SHF (NSHF) group. Assignment was determined by whether the heart rate or mean arterial pressure increased by more than 20% from baseline during the intubation process.

To evaluate the predictive performance of both the PI alone and the PI ratio, the researchers analysed the data using receiver operating characteristic (ROC) curves. The results indicated that the PI alone had limited predictive capability, with an area under the ROC curve (AUC) of 0.630, with a 95% confidence interval ranging from 0.523 to 0.737. At a cut-off value greater than 5.50, the PI alone demonstrated a sensitivity of 46.5% and a specificity of 76.7% for predicting the timing of endotracheal intubation.

In contrast, the PI ratio demonstrated moderate predictive performance with a higher AUC of 0.775, with a 95% confidence interval of 0.676 to 0.874. A PI ratio greater than 3.623 was identified as a potential predictor of a haemodynamically suitable state for intubation. This specific cut-off value yielded a sensitivity of 88.0% and a specificity of 60.0%. The higher AUC suggests that the ratio provides a better discrimination between children who experience significant haemodynamic fluctuations and those who do not, compared to the raw PI values.

The study also examined the occurrence of intubation-related adverse events. All such events were observed exclusively in the significant haemodynamic fluctuation group. This finding underscores the clinical relevance of identifying haemodynamic instability, as it is directly associated with adverse outcomes during the airway management process.

The authors concluded that the PI ratio can help mitigate the influence of individual baseline PI variability, making it more suitable for predicting a stable haemodynamic response to endotracheal intubation in children. They noted that while the PI ratio shows a higher AUC than the PI alone, it may serve as a useful adjunct to clinical assessment rather than a standalone diagnostic tool.

Despite the promising results, the authors emphasized that further multicentre validation is required before the PI ratio can be implemented routinely in clinical practice. The current study was conducted as an observational study in a specific population of children aged four to ten years undergoing daytime surgery. The findings are limited to this demographic and procedural context, and the generalizability of the results to other age groups, surgical settings, or anaesthetic protocols remains to be determined. The study was registered with the Chinese Clinical Trial Registry under the number ChiCTR2500107129.

Subject of Research: Evaluation of the perfusion index ratio as a predictor for haemodynamic stability during pediatric endotracheal intubation.

Article Title: Assessment of the PI ratio for predicting the timing of endotracheal intubation: an observational study

Article References: Xu, H., Huang, Y., Jiang, F., Hu, J., Wang, L., Zhang, Y., Ou, L., & Wang, Q. (2026). Assessment of the PI ratio for predicting the timing of endotracheal intubation: an observational study. BMC Anesthesiology. https://doi.org/10.1186/s12871-026-04351-4

Image Credits: AI Generated

DOI: 10.1186/s12871-026-04351-4

Keywords: pediatric anesthesia, perfusion index, endotracheal intubation, haemodynamic stability, observational study, airway management, clinical prediction, BMC Anesthesiology, Assessment, ratio, predicting, timing