Abstract 371: Using Defibrillator Bioimpedance Waveforms to Measure Ventilation During Continuous Chest Compression CPR

Abstract

Introduction: For patients with out of hospital cardiac arrest, prompt return of circulation and ventilation is vitally important for survival. Techniques and devices have been developed to ensure emergency responders are providing high quality chest compression, but there has been little progress in the area of ventilation. Until an advanced airway is placed, there has been no practical way to measure ventilation. The aim of this study is to develop a method to measure ventilation during continuous chest compressions cardiopulmonary resuscitation (CPR) that can be used to monitor and improve quality of ventilation during out of hospital CPR. Hypothesis: Defibrillator transthoracic bioimpedance can be used to identify ventilation waveforms prior to placement of an advanced airway during continuous chest compressions CPR. Methods: We examined 391 patients’ defibrillator files from four Resuscitation Outcomes Consortium sites for the presence of waveforms that met previously developed criteria and were manually annotated. Criteria for an acceptable ventilation waveform were: waveform amplitude ≥0.5 Ohm and waveform duration ≥1 sec. We recorded the number of ventilations, return of spontaneous circulation, initial heart rhythm, and ventilation rates. Following annotation, 333 of the 391 patients’ files had the necessary intubation time recorded and an automated program precisely measured the amplitude and duration of each ventilation. We determined mean (±SD) waveform amplitude and duration of inflation and deflation pre and post airway placement. Significance was determined using Wilcoxon ranked sum test. Results: Comparing the pre and post airway measurements did not result in any significant differences, except in duration of inflation, which was 1.06 ± 0.41 sec and 1.11 ± 0.52 sec, respectively, (p <0.001). Ventilation waveforms had significantly lower amplitude and shorter duration during chest compressions than during pauses in compressions. Conclusion: Defibrillator transthoracic bioimpedance can be used to identify and monitor ventilations during continuous chest compressions CPR. Ventilation waveforms have lower amplitudes and shorter durations during chest compressions than during pauses in compressions.