​For the critical outcomes of ROSC, survival at hospital discharge, and survival with favorable neurologic/functional outcome, we found no evidence to address the question. For the important outcome of coronary perfusion pressure, we found 3 observational studies: 2 in animal models(Yannopoulos 2005, 363; Zuercher 2010, 1141) and 1 in anesthetized children not in cardiac arrest,(Glatz 2013, 1674) which provided very-low-quality evidence, downgraded for serious risk of bias and very serious indirectness. All 3 studies reported a reduced coronary perfusion pressure with incomplete chest recoil. In anesthetized children undergoing mechanical ventilation during cardiac catheterization, Glatz et al analyzed the effect of leaning by applying a force on the chest corresponding to 10% and 20% of body weight; this resulted in a proportional reduction in coronary perfusion pressure.(Glatz 2013, 1674) Yannopoulos et al and Zuercher et al reported in swine models of VF that leaning on the chest precluding full chest recoil reduced the coronary perfusion pressure in a dose-dependent manner.(Yannopoulos 2005, 363; Zuercher 2010, 1141) For the important outcome of cardiac output/cardiac index, we found 2 observational studies (1 in an animal model and 1 in anesthetized children not in cardiac arrest) also representing very-low-quality evidence downgraded for serious risk of bias and very serious indirectness.(Zuercher 2010, 1141; Glatz 2013, 1674) The study in animals reported a proportional reduction in cardiac index when 10% and 20% of the forces applied during compression remained between compressions.(Zuercher 2010, 1141) In contrast, Glatz et al found that leaning forces had no effect on cardiac output.(Glatz 2013, 1674)