Hands-off Intervals during Cardiopulmonary Resuscitation: Duration and Effect on the ECG Analysis

Recent works are aimed at development of shock advisory systems (SAS) for automated external defibrillators (AEDs), which continuously analyze the electrocardiogram (ECG) during non-interrupted chest compressions (CC). Being also part of the cardiopulmonary resuscitation (CPR), small 'hands-off' intervals (CC pauses) for insufflations are interrupting the CC, and thus the SAS analysis process. This study is applied on 530 CC-contaminated ECG strips taken from 168 patients who undergo out-of-hospital resuscitation interventions with AEDs. A statistical study of the short duration CC pauses is performed, showing non-normal distribution with median value of 4 seconds, quartile range between 3 and 5 seconds, min-max range between 1 and 10 seconds. Another focus is the effect of skipping the CC pauses on the SAS accuracy by supplying continuous non-linear CC-corrupted ECG signal for analysis. The SAS is tested with different coupling intervals [t1, t2], where t1 is the time before the CC pause, t2 is the time after the CC pause, t1+t2=10 seconds. The SAS accuracy on CC-corrupted linear signals [10s+0s] compared to non-linear signals [9s+1s], [8s+2s], [7s+3s], [6s+4s], [5s+5s] shows insignificant difference (p>0.05) for the different arrhythmia: ventricular fibrillation between 86% and 90.3%, normal rhythms between 88.4% and 93.5%, asystole between 80.4% and 87.3%. Several examples illustrate the performance of the SAS analysis process on various CC artefacts and ECG arrhythmias.