Resuscitation 80 (2009) 463–469 Contents lists available at ScienceDirect Resuscitation journal homepage: www.elsevier.com/locate/resuscitation Experimental paper Comparison of mechanical characteristics of the human and porcine chest during cardiopulmonary resuscitation  Andreas Neurauter a , Jon Nysæther c , Jo Kramer-Johansen d , Joar Eilevstjønn c , Peter Paal a , Helge Myklebust c , Volker Wenzel a , Karl H. Lindner a , Werner Schmölz b , Morten Pytte d , Petter A. Steen d , Hans-Ulrich Strohmenger a,∗ a Department of Anesthesiology and Critical Care Medicine, Innsbruck Medical University, Anichstrasse 35, 6020 Innsbruck, Austria b Department of Trauma Surgery and Sports Medicine, Innsbruck Medical University, Innsbruck, Austria c Laerdal Medical AS, Stavanger, Norway d Institute for Experimental Medical Research, Department of Anaesthesiology and Pre-hospital Division, Ulleval University Hospital and University of Oslo, Oslo, Norway article info Article history: Received 26 November 2007 Received in revised form 29 September 2008 Accepted 12 December 2008 Keywords: BLS ALS CPR Cardiac arrest Chest compression Chest compression depth abstract Background: Most studies investigating cardiopulmonary resuscitation (CPR) interventions or functional- ity of mechanical CPR devices have been performed using porcine models. The purpose of this study was to identify differences between mechanical characteristics of the human and porcine chest during CPR. Material and methods: CPR data of 90 cardiac arrest patients was compared to data of 14 porcine from two animal studies. Chest stiffness k and viscosity  were calculated from acceleration and pressure data recorded using a Laerdal Heartstart 4000SP defibrillator during CPR. K and  were calculated at chest compression depths of 15, 30 and 50mm for three different time periods. Results: At a depth of 15 mm porcine chest stiffness was comparable to human chest stiffness at the begin- ning of resuscitation (4.8 vs. 4.5 N/mm) and clearly lower after 200 chest compressions (2.9 vs. 4.5 N/mm) (p < 0.05). At 30 and 50 mm porcine chest stiffness was higher at the beginning and comparable to human chest stiffness after 200 chest compressions. After 200 chest compressions porcine chest viscosity was similar to human chest viscosity at 15mm (108 vs. 110Ns/m), higher for 30mm (240 vs. 188Ns/m) and clearly higher for 50 mm chest compression depth (672 vs. 339 Ns/m) (p < 0.05). Conclusion: In conclusion, human and porcine chest behave relatively similarly during CPR with respect to chest stiffness, but differences in chest viscosity at medium and deep chest compression depth should at least be kept in mind when extrapolating porcine results to humans. © 2009 Elsevier Ireland Ltd. All rights reserved. 1. Introduction During cardiopulmonary resuscitation (CPR), closed chest com- pressions are performed to maintain coronary and cerebral perfusion, and several animal studies have shown that quality and performance of CPR correlate directly with survival from cardiac arrest. 1–3 CPR guidelines recommend a chest compression depth of 4 to 5 cm for adults independently of sex, body size, and physical status. 4 In the past, many CPR experiments were performed in canine mod- els, but porcine models are currently more popular. Also, rodent models are good screening tools, but they are too small in scale to allow direct extrapolation to humans. Thus, most experimental CPR  “A Spanish translated version of the summary of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2008.12.014”. ∗ Corresponding author. Tel.: +43 512 504 22400; fax: +43 512 504 22450. E-mail address: hans.strohmenger@i-med.ac.at (H.-U. Strohmenger). studies in the last 20 years have been performed using porcine mod- els with extrapolation to human CPR irrespective of comparability between the human and porcine body. Unfortunately, many inter- ventions that were highly effective in CPR laboratories have failed in clinical studies. 5–7 While some of these effects have been attributed to differences between “laboratory CPR” and “real life CPR on the street”, 8 differences in chest configuration between humans and pigs are poorly understood, but may explain, in part, the observed problems to extrapolate interventions from bench to bedside. The purpose of this study was to identify differences in mechan- ical characteristics of the human and porcine chest during CPR. 2. Materials and methods 2.1. Human data The raw human data were obtained from an observational prospective study of out of hospital cardiac arrest patients between October 2004 and June 2005. 9 Approval for this study was obtained 0300-9572/$ – see front matter © 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.resuscitation.2008.12.014