Kinetics of manual and automated mechanical chest compressions

Aim: Early onset of adequate chest compression is mandatory for cardiopulmonary resuscitation (CPR) following cardiac arrest. Transmission of forces from chest strain to the heart may be variable between manual and mechanical chest compressions. Furthermore, automated mechanical chest devices can deliver an active decompression, thus improving the venous return to the heart. This pilot study investigated the kinetics of cardiac deformation during these two CPR methods.

Methods: Transesophageal echocardiographic analysis of the right ventricular wall behind the sternum during CPR was assessed during manual and mechanical chest compression in adult patients admitted to the emergency department for out-of-hospital cardiac arrest.

Results: 9 patients had manual and 11 mechanical chest compression. Mechanical chest compression was characterized by greater right ventricular lateral wall displacement [with a median (IQR) of 3.7 (3.12-4.27) vs. 2.53 (2.27-2.6) cm, p < 0.0001], and lower rising time [123 (102-169) vs. 187 (164-215) ms, p = 0.002], relaxing time [109 (102-127) vs. 211 (133-252) ms, p = 0.0003], compression rate [100.6 (99.6-102.2) vs. 131.9 (125.4-151.4) bpm, p < 0.0001], with compression-decompression time ratio of [1.04 (0.86-1.1) vs. 0.86 (0.78-0.96), p = 0.046].

Conclusion: Mechanical compared to manual chest compression delivered a more rapid compression and decompression of the cardiac structures at an adequate rate, with broader inward-outward movement of the ventricular walls suggesting greater emptying and filling of the ventricles. Transesophageal echocardiography may be a useful tool to assess the adequacy of chest compression without CPR interruption.