Objective: To investigate whether real-time audio and visual feedback during cardiopulmonary resuscitation outside hospital increases the proportion of subjects who achieved prehospital return of spontaneous circulation.
Design: A cluster-randomised trial.
Subjects: 1586 people having cardiac arrest outside hospital in whom resuscitation was attempted by emergency medical services (771 procedures without feedback, 815 with feedback).
Setting: Emergency medical services from three sites within the Resuscitation Outcomes Consortium in the United States and Canada.
Intervention: Real-time audio and visual feedback on cardiopulmonary resuscitation (CPR) provided by the monitor-defibrillator.
Main outcome measure: Prehospital return of spontaneous circulation after CPR.
Results: Baseline patient and emergency medical service characteristics did not differ between groups. Emergency medical services muted the audible feedback in 14% of cases during the period with feedback. Compared with CPR clusters lacking feedback, clusters assigned to feedback were associated with increased proportion of time in which chest compressions were provided (64% v 66%, cluster-adjusted difference 1.9 (95% CI 0.4 to 3.4)), increased compression depth (38 v 40 mm, adjusted difference 1.6 (0.5 to 2.7)), and decreased proportion of compressions with incomplete release (15% v 10%, adjusted difference -3.4 (-5.2 to -1.5)). However, frequency of prehospital return of spontaneous circulation did not differ according to feedback status (45% v 44%, adjusted difference 0.1% (-4.4% to 4.6%)), nor did the presence of a pulse at hospital arrival (32% v 32%, adjusted difference -0.8 (-4.9 to 3.4)), survival to discharge (12% v 11%, adjusted difference -1.5 (-3.9 to 0.9)), or awake at hospital discharge (10% v 10%, adjusted difference -0.2 (-2.5 to 2.1)).
Conclusions: Real-time visual and audible feedback during CPR altered performance to more closely conform with guidelines. However, these changes in CPR performance were not associated with improvements in return of spontaneous circulation or other clinical outcomes. Trial Registration Clinical Trials NCT00539539.