(854) Association Between Heart Rate Variability and Need for Mechanical Ventilation in Bronchiolitis

Introduction: Low heart rate variability (HRV) is associated with poor outcomes in critically ill children. However, the utility of HRV in discriminating outcomes for patients admitted to the PICU for bronchiolitis remains unknown. Thus, the objective of this study was to determine whether HRV can discriminate the need for mechanical ventilation or non-invasive positive pressure ventilation (NIPPV).

Methods: This was a retrospective, observational cohort study on PICU patients younger than 24 months who were on high-flow nasal cannula and had continuous heart rate data available from bedside monitors (2012-2022). HRV was measured using age-normalized z-scores of the integer HRV (HRVi), defined as the standard deviation of the heart rate sampled every second over 5 consecutive minutes. The primary outcome was mechanical ventilation by day 7 of PICU admission, and the secondary outcome was NIPPV or mechanical ventilation by day 7. Statistical analysis was performed using Wilcoxon Rank Sum Test and logistic regression. Performance was assessed using the area under the receiver operating characteristic (AUROC) and precision-recall curves (AUPRC).

Results: A total of 1,488 patients were included. Ninety-seven patients (6.5%) required mechanical ventilation and 167 (11.2%) required either NIPPV or mechanical ventilation. Median HRVi was significantly lower in those requiring mechanical ventilation (p < 0.001) and NIPPV or ventilation (p < 0.001), with odds ratios of 0.29 (95% CI: 0.18-0.46) and 0.46 (95% CI: 0.32-0.65), respectively. The area under the receiver operating characteristic curve for median HRVi was 0.69 (95% CI: 0.62-0.76) for mechanical ventilation and 0.62 (95% CI: 0.56-0.68) for NIPPV or ventilation. The area under the precision-recall curve for median HRVi was 0.015 (2.4 times higher than prevalence) for mechanical ventilation and 0.020 (1.8 times higher than prevalence) for NIPPV or ventilation.

Conclusions: Median HRVi in a 6-hour block was significantly lower in patients who required mechanical ventilation and has moderate performance in discriminating the need for mechanical ventilation in next 6-hour block.