Abstract Body:
Background
Pediatric out-of-hospital cardiac arrests (OHCA) have high morbidity and mortality. More than 5000 children have a nontraumatic OHCA annually in the United States and survival to discharge is 3-9%. During the initial stage of CPR before advanced airway placement, emergency medical services (EMS) providers use bag mask ventilation (BMV) to support airway and breathing. Bioimpedance is a recently validated method to measure BMV during CPR. As the chest wall expands and contracts during BMV, thoracic electrical resistance or bioimpedance oscillates and is recorded via defibrillation pads. Ventilation is measured during CPR chest compression pauses. Good ventilation is associated with improved outcomes in adult OHCA but has not been studied in children with bioimpedance.

Hypothesis
The incidence of lung inflation in pediatric OHCA BMV is low.

Aim
To determine the incidence of lung inflation in BMV during pediatric OHCA CPR using bioimpedance

Methods
This was a retrospective observational study using EMS patient care records, EMS defibrillator files and hospital records. Inclusion criteria were <18yo medical OHCA patients that an EMS agency responded to in 2020-2022 with ≥2 min thoracic bioimpedance recorded on a defibrillator file. Traumatic OHCA or cases with excessive bioimpedance artifact were excluded. Adequate ventilation waveforms were defined as waveforms with bioimpedance amplitude ≥0.5Ω and duration ≥1s. Pauses were 3-15s breaks in chest compressions. Ventilation incidence was measured in 2 groups: patients with <50% (group 1) and ≥50% (group 2) compression pauses with ventilation waveforms. Data were presented descriptively with medians.

Results
We assessed 161 patients for eligibility and 59 were included. Median age was 12 months (IQR 3-75.5) and 54% were male. Group 1 had 103 and group 2 had 209 ventilations. Group 1 had 313 and group 2 had 147 compression pauses. There were 0.29 (IQR 0.13-0.73) ventilations per compression pause per patient. Group 1 had 7 (IQR 5-11) and group 2 had 6.5 (IQR 4-10.75) compression pauses per patient while Group 1 had 1 (IQR 0-3) and group 2 had 12.5 (IQR 4.75-17.50) ventilations per patient. Of cases with outcomes available for review, ROSC occurred in 28.57% (n=8/28) of cases in group 1 and 37.50% (n=6/16) of cases in group 2.

Conclusion
BMV lung inflation is infrequent in pediatric OHCA. Increased ventilation may be associated with higher rates of ROSC, but larger sample sizes are needed.