Abstract 1775: Transthoracic Impedance Used as a Tool to Evaluate Performance of Cardiopulmonary Resuscitation
Introduction: There is a need to evaluate the cardiopulmonary resuscitation (CPR) process without using extra equipment in order to document if ambulance personnel follow CPR guidelines. We wanted to do this by using technology based on changes in transthoracic impedance produced by chest compressions and ventilations.
Methods: 122 incidents of out-of-hospital cardiac arrest between May 2003 and February 2004 were analysed based on data recorded from ambulance defibrillators (LIFEPAK® 12 defibrillator/monitor, Medtronic, WA) in Oslo EMS. Both cardiac and non-cardiac arrests were included. New software (CODE-STAT™ Beta 6.0 V2, Medtronic) was used to analyse chest compressions and ventilations based on changes in thoracic impedance between the defibrillator pads. ECG and other event data were also collected.
Results: 25 ± 14% (varying from 76% to 3%) of the time chest compressions were not performed on patients without spontaneous circulation (NFR = No Flow Ratio). When adjusting for time spent on analysis of ECG, pulse check and defibrillation, NFR was 20 ± 13% (varying from 70% to 3%). Mean compression rate per minute was 87 ± 16; correspondingly the compression rate during active compression performance was 117 ± 9/min. Individual variation was 31 to 117/min (mean) and 95 to 144/min (active periods) respectively. A mean of 14 ± 3 ventilations/min was recorded. This number varied from 8/min to 26/min. Compared with the rest of the episode, the first 5 minutes had a significantly higher amount of time without chest compressions; 30 ± 17% (p < 0,001) and significantly lower mean compression and ventilation rates; 80 ± 19/min and 12 ± 4/min respectively (p < 0,001 in both cases). There was no significant difference in compression rate during active compression performance (p = 0.07).
Conclusions: This is the first study documenting CPR quality using transthoracic impedance. NFR was 25% and 20% adjusted with great rescuer variability.