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Re: Auditory and visual prompts during CPR in the Emergency Department

Dear Editor,

We read with interest Williamson et al. [1] study on the use of audio prompts in automatic external defibrillators to improve cardiopulmonary resuscitation (CPR) in untrained & trained lay subjects. We report a study from an emergency department (ED) using trained ED staff (doctors & nurses) and paramedics.

Through our own departmental video audit we have observed great variability in the rate of external cardiac compressions (ECC); median 140 compressions per minute (cpm) & range 100-180 cpm. This rapid rate of ECC is of concern since it is faster than the recommended 100cpm [2]. Studies suggest that rescuers may fatigue after only 1 minute of CPR [3] and there is an associated decline in the quality of chest compressions with time [4].

We undertook 2 separate studies to test specifically whether a piece of music influenced the rate of ECC when compared to nothing and a metronome and another study to test whether using a specially adapted clock compared to a metronome influenced the rate of ECC. In both studies participants were video taped whilst performing CPR on an intubated resuscitation manikin for 3 minutes in the resuscitation bay of the Emergency Department and the rate of ECC subsequently analysed by using video playback.

In the first study 50 participants were randomised in blocks of 5 to listen to a minute of silence followed by a second minute of a randomly selected piece of music and then a final minute of a recording of a metronome set at a 100 beats per minute (bpm). Participants were not told that the metronome was set at 100bpm. Three pieces of music had a rate of 100bpm and one much less than 100bpm and another much faster than 100bpm. In the second study 43 participants were randomised (blocks of 10) to two groups either metronome or ‘resuscitation-clock’. The metronome group listened to a minute of silence followed by 2 minutes of a recording of a metronome set to 100bpm. The ‘resuscitation-clock’ group listened to a minute of silence and were then asked to look at the ‘resuscitation-clock’ and use it to help time the rate of ECC. The resuscitation clock was essentially a normal clock with the numerals removed and the figures 25, 50, 75 and 100 placed at 3, 6, 9 & 12 o-clock respectively.

In the first study the rate of ECC was not statistically different between either the silence, music or metronome groups (Freidmans test X2=3.6, p=0.16), range 54-156, median 116cpm. Those participants who had received formal CPR training within 3 months of taking part in the study did not have a statistically different rate of ECC compared to those without recent training (Mann-Whitney U test=139. p=0.14). In the second study the metronome group achieved the target compression rate with a mean of 99.8 (95% CI 99.2 to 100.4), compared to clock group mean 106.9 (95% CI 101.6 to 112.2) and the control (silence) group mean 114.6 (95% CI 109.6 to 119.3).

We concluded that without the use of auditory prompts trained ED personnel are poor at performing ECC at 100bpm even if recent formal CPR training has taken place. The use of a simple auditory prompt can help trained personnel perform ECC at the correct rate.

References

1. Williamson et al. Effects of automatic external defibrillator audio prompts on cardiopulmonary resuscitation performance. Emerg Med J 2005; 22: 140-143.

2. Lockey A, Nolan J. Cardiopulmonary resuscitation in adults. BMJ 2001; 323:819-820.

3. Javier Ochoa F, Ramalle-Gomora E, Lisa V, Saralegui I. The effect of rescuer fatigue on the quality of chest compressions. Resuscitation 1998;37:149-52.