104 - Real-time measurement of heart rate variability and complexity parameters in VLBW neonates towards predicting extubation success

Poster Number: 104
Publication Number: 104.2137

Background: Predicting extubation success can mitigate neonatal reintubation morbidities. One posited factor is autonomic fitness. Prior assessment of heart rate variability in the 24 hours before extubation associates variability with extubation success, however this has required off-line retrospective data analysis.

Objective: To establish the feasibility of using real time measures of heart rate variability, complexity, and entropy before extubation to predict extubation success.

Design/Methods: 34 VLBW infants, GA 22-30w, BW < 1500g, were evaluated using ICON (TM, Osypka Medical, Cardiotronic) monitors during extubation to non-invasive support. Heart rate variability [HRV, SD of normal-to-normal RR], complexity [HRC, entropy of 200 consecutive beats], multiscale entropy [MSE, measuring self-similarity], and interval-based distance ratio [PNN, assessing successive RR above 50 ms] were measured continuously, in the hour before and after extubation. Successful neonates were compared vs those reintubated in 72 hours.

Results: Successfully extubated neonates had similar GA and weight, but earlier PMA and statistically but not clinically higher BP at extubation vs failure (Table I). Pre-extubation HRV, MSE, and PNN but not HRC were higher in successful extubations vs failure (Figure I), with means: HRV success= 14.1 v HRV fail= 9.1 (p < 0.03), MSE success= 2.16 v MSE fail= 1.25 (p < 0.05), PNN success= 1.54 v PNN fail= 0.66 (p < 0.05). No parameters differed based on success in the hour after extubation. Pairwise comparison showed no difference in HRV, HRC, MSE, and PNN pre vs post-extubation, when successful. Failure was associated with an increase in HRC (HRC pre= 0.2 v HRC post=0.225, p=0.023) and MSE (MSE pre= 1.25 v MSE post=1.44, p=0.009) post-extubation vs pre. Pre-extubation ROC revealed an AUC of 0.8036 for HRV, 0.7619 for MSE, and 0.7738 for PNN (Figure II). Correlation of GA and PMA with HRV was weak, 0.07 and 0.17 respectively.

Conclusion(s): In summary, higher HRV, MSE and PNN pre-extubation correlated with future successful extubation due to the natural balance between sympathetic/parasympathetic tone; whereas more variability in complexity and entropy after extubation was associated with reintubation. We interpret this to reflect increased work of breathing (increased VI, pH, RR & pCO2) causing elevated demands on cardiac output and patient fatigue. HRV may also reflect autonomic maturation, with variable age-related improvement that may inform cardiovascular readiness to wean breathing support. We conclude this is a novel tool to assist extubation evaluation with real-time heart rate variability measures.