The first description of modern cardiopulmonary resuscitation (CPR) included the instruction to compress the chest “about 60 times per minute”1; however, the optimal compression rate was unknown. Franz Koenig is credited with describing the original technique for external cardiac massage, which included a compression rate of 30 to 40 per minute.2 But in the first published description of external cardiac massage in 1892, Friedrich Maass documented a better clinical response with a rate of 120 per minute.2 To this day, the optimal compression rate is the subject of controversy. Animal data indicate that cardiac output increases with compression rates up to as high as 150 per minute.3 In a canine model of prolonged cardiac arrest, compression rates of 120 per minute compared with 60 per minute increased mean aortic (systolic and diastolic) and coronary perfusion pressures, and 24-hour survival (61% versus 15%, P =0.03).4 In a study of 9 patients undergoing CPR, a compression rate of 120 per minute generated higher aortic peak pressures and coronary perfusion pressures compared with a compression rate of 60 per minute (the rate recommended by the 1980 American Heart Association [AHA] guidelines). This evidence is supported by another study of 23 patients in cardiac arrest in which compressions at 120 per minute resulted in significantly higher end-tidal carbon dioxide values compared with compressions at 80 per minute.5 Article see p 3004 The first large, prospective, observational study of the influence of chest compression rate on patient survival was published in this journal in 2005.6 The number of delivered chest compressions was recorded by trained observers during in-hospital resuscitation attempts. A higher chest compression rate was associated with a higher rate of return of spontaneous circulation (ROSC). The mean chest compression rate for initial survivors was 90 …