Abstract 261: Correction for Body Displacement for Accurate Delivery of Chest Compressions: Accuracy of the Truecpr Device on a Soft Mattress

Abstract

Objective: Accelerometer based chest compression feedback devices overestimate compression depth by not accounting for a soft surface below the victim. TrueCPR, a new real-time feedback device, provides visual feedback on compression depth, based on measured changes in magnetic field strength between a backpad and a chestpad. We determined accuracy of that method on a calibrated test bench and on a manikin on a soft surface. Methods: First, we used a calibrated, computerized drill press compressing a Laerdal Resusci Anne SkillReporter manikin on a firm surface to verify calibration of its compression depth measurement, and to measure accuracy of the TrueCPR device. Then, we compared measurements of two feedback devices (TrueCPR and a sternum-only accelerometer) on a standard inflatable hospital mattress. Thirty manual chest compressions were given with feedback of TrueCPR or the accelerometer, to achieve the recommended depth of 50-60 mm and compared with the compression depth measured by the manikin. Results: Compared to the drill press, the manikin measured compression depth with error <1 mm for depths below 55 mm and with 1-2 mm underestimation above 55mm. TrueCPR showed a systematic underestimation of 3-4 mm on a hard surface. On the mattress, TrueCPR showed an underestimation of 2-4 mm, where the accelerometer showed an overestimation of 17-23 mm (figure). A compression depth in the recommended range was achieved with TrueCPR in 23 of 30 compressions and with the accelerometer in 2 of 30 compressions. Conclusion: TrueCPR measures depth independent of the stiffness of the surface upon which the CPR is being performed with a constant underestimation of <4 mm. A sternum-only accelerometer substantially overestimates depth when performing CPR on a soft surface. Correction for body displacement on a soft surface is essential for accurate delivery of chest compressions within the recommended depth range.