Abstract 290: Cardiopulmonary Resuscitation Duty Cycle in Out-of-Hospital Cardiac Arrest
Background: CPR duty cycle is the portion of time spent in compression relative to the total time of the compression-decompression cycle. Guidelines recommend a 50% duty cycle based largely on animal investigation. Little is known about duty cycle in human resuscitation and whether duty cycle correlates with other CPR measures.
Methods: We calculated the duty cycle, compression depth, and compression rate during EMS resuscitation of 164 patients with out-of-hospital ventricular fibrillation cardiac arrest. We captured force recordings from a chest accelerometer to measure ten-second CPR epochs that immediately preceded each scheduled rhythm analysis. Duty cycle was calculated using two methods. The effective compression time (ECT) is the time from beginning to end of compression divided by total period for that compression-decompression cycle. The area duty cycle (ADC) is the ratio of area under the force curve divided by total area of one compression-decompression cycle. We evaluated the compression depth and compression rate according to duty cycle quartiles.
Results: There were 369 ten-second epochs among 164 patients. The median duty cycle was 38.8% (SD=5.5%) using ECT and 32.2% (SD=4.3%) using ADC. A relatively shorter compression phase (lower duty cycle) was associated with greater compression depth (test for trend < 0.05 for ECT and ADC) and slower compression rate (test for trend < 0.05 for ADC) (Table). Sixty-one patients (37%) survived to hospital discharge.
Conclusions: In this system with high survival, duty cycle was well below the 50% recommended guideline, and was associated with compression depth and rate. These findings provide rationale to incorporate duty cycle into future research to evaluate how CPR influences resuscitation.
Author Disclosures: T. Rea: Research Grant; Modest; Philips, Medtronic Foundation, Laerdal Foundation. B. Johnson: None. J. Coult: None. C. Fahrenbruch: None. J. Blackwood: None. L. Sherman: None. P. Kudenchuk: None. M. Sayre: None.
- © 2014 by American Heart Association, Inc.