Background Goal of the study:: The quality of chest compressions during cardiopulmonary resuscitation increases chance of survival and improves outcomes1. The goal of the study was to compare the efficacy of a smartphone metronome application and the musical mental metronome "La Macarena" to improve the quality of chest compressions.
Material and methods: A controlled, cluster sampling study of 2 minutes of continuous chest compressions on manikin was conducted with medical students, University of Barcelona.  Subjects received no guidance (control), metronome app programmed at 103 bpm (App) or the order to perform compressions to the mental cadence of the song “La Macarena” (Maca). Demographic data, quality of chest compressions (Resusci Anne Wireless SkillReporter® Software) and a satisfaction survey were registered. Intention-to-treat (ITT) and per-protocol (PP) analyses were performed.
Results: 164 students were included (control ITT=71, PP=35; App=45; Maca=48). Groups were homogeneous except for sex (men, control ITT 46,5%, App 31,1%, Maca 22,9%, p=0.024; control PP 48,6%, p=0.048) and BMI (control PP 22,09, App 20,2, Maca 21,66 Kg/m2, p=0.038). The percentage of compressions between 100 and 120 per minute was significantly higher in the App (91 [87; 94]) and Maca (74 [8; 98]) than in the control group (ITT 24 [1; 92], PP 7 [0.64], p <0.001, p = 0.023 and p <0.001, p = 0.001). Any group reached the depth of 5 cm. The App group had the better overall quality compression scores (basic 25%, intermediate 60,4%, advanced 14,6%) but the longer onset delay of the first compression (4,3 [3,5;5,5] seconds). Students rated the app as the most useful help method.
Conclusions: Metronome app and mental metronome "La Macarena" improved the quality of chest compressions by increasing the proportion of adequate rate but not the depth of compressions. The metronome app was more effective but with a significant onset delay.

1.-Perkins GD, Handley AJ, Koster RW, et al. Resuscitation. 2015;95:81-99. 


02 / Efficacy of metronome app and mental metronome “La Macarena” to improve the quality of chest compressions