Alternatives to Estimate the Compression Depth from the Acceleration Signal during Cardiopulmonary Resuscitation

Feedback devices improve the quality of chest compressions during cardiopulmonary resuscitation. Most devices use accelerometers to estimate the chest displacement using double integration and additional reference signals to ensure the stability of the process. We described and evaluated three novel methods for computing the compression depth using solely the acceleration signal. The BPF method approximates the integration using a band-pass filter. The ZCV method computes the velocity and calculates the depth from the zero-crossing instants of each compression cycle. The SAA method computes the depth from the spectral analysis of the acceleration signal. We gathered twelve 10-min records in which chest compressions were provided on a manikin equipped with a displacement sensor. A tri -axial accelerometer was placed beneath the rescuer´s hands. The median (IQR) unsigned error in mm between the computed depth and the reference was 4.0 (2.1-6.2), 3.9 (2.0-6.2), and 1.2 (0.6-2.1) for each method, respectively. Compression depth can be accurately estimated from chest acceleration. The spectral analysis method provided the best global performance. This alternative could be implemented for real time feedback during CPR.