697: DIAPHRAGM SURFACE ELECTROMYOGRAPHY IN CHILDREN: PILOT STUDY OF MARKERS OF WORK OF BREATHING

Abstract

Introduction: Surface electromyography (sEMG) of the diaphragm has emerged as a method to quantify work of breathing (WOB) in the intensive care unit. While sEMG patterns of respiratory distress have been well characterized in adults, the technique in pediatric and neonatal populations is limited. We recorded sEMG of the diaphragm in intubated pediatric patients, and correlated the measurements with subjective and objective markers of WOB. Methods: This study was approved by the Institutional Review Board at Boston Children’s Hospital. We enrolled intubated pediatric patients (0-18 years old) in the Medical-Surgical Intensive Care Unit. We excluded patients who received chemical neuromuscular blockade or required fractional inspired oxygen >0.60. A bipolar sEMG signal was recorded from the diaphragm of enrolled subjects for five minutes per session. The P0.1 value (the pressure during occlusion of the airway 100 milliseconds after the start of inspiration) and a subjective evaluation of WOB (assessed by the bedside nurse, parent, and physician on a four-point Likert scale, with 0 meaning no WOB and 3 meaning high WOB) were obtained. Using post-hoc spectral analysis in MATLAB (R2019), the electrocardiography signal of the EMG was filtered, and the root-mean-square (RMS) was calculated. Results: We obtained 42 sEMG recordings in 22 patients. The median (interquartile range) WOB rating was 0 (0, 0). The mean (+/- standard deviation) P0.1 0.75 (+/- 0.79) cmH2O and RMS 0.016 (+/- 0.007) mV are like published values for subjects with comfortable WOB described in the literature. Linear regression between P0.1 and RMS shows a positive association with R2 (95% confidence interval) of 0.22 (0.03, 0.70), p>0.05. Conclusions: In this pilot evaluation, we have identified a positive association between sEMG of the diaphragm and P0.1, and we cannot exclude the possibility that the P0.1 accounted for up to 70% of the variation in RMS. Most subjects exhibited low respiratory effort, which may reflect our sedation regimen. Future studies should characterize sEMG in subjects with higher levels of WOB. In addition, the effect of chronic low respiratory effort in intubated patients on long-term respiratory mechanics needs to be further assessed, as well as the value of sEMG in determining extubation readiness.