Automatic detection of chest compression pauses using the transthoracic impedance signal

The recommended treatment for out-of-hospital cardiac arrest (OHCA) is immediate cardiopulmonary resuscitation (CPR) and early electrical defibrillation. During CPR, chest compressions and ventilations should be provided with a compression-ventilation ratio of 30:2. Chest compressions and ventilations induce fast and slow fluctuations, respectively, on the transthoracic impedance (TTI). In this work we present a method for the automatic detection of pauses in chest compression using the TTI. The fuctuations induced by chest compressions were first isolated and emphasized and then, using an adaptive threshold, the intervals without chest compressions were identified. The method was adjusted and evaluated using a dataset of 3596 pauses corresponding to OHCA episodes. The mean duration of the pauses was 7.0 ± 6.2 s. For the test set, the sensitivity and the positive predictive value were 93.9% and 96.2%, respectively. This method could be used for both online and offine CPR quality evaluation or to detect artifact free ECG intervals in which a rhythm assesment could be launched.