Auditory and visual prompts during cardiopulmonary resuscitation in the emergency department

We read with interest Williamson et al's¹ study on the use of audio prompts in automatic external defibrillators to improve cardiopulmonary resuscitation (CPR) in untrained and trained lay subjects. We report a study from an emergency department (ED) using trained ED staff (doctors and 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 100 cpm.² Studies suggest that rescuers may fatigue after only one minute of CPR³ and there is an associated decline in the quality of chest compressions with time.⁴

We undertook two separate studies to test specifically (a) whether a piece of music influenced the rate of ECC when compared with nothing and a metronome and (b) whether using a specially adapted clock influenced the rate of ECC when compared with a metronome. In both studies participants were videotaped while performing CPR on an intubated resuscitation manikin for three minutes in the resuscitation bay of the ED. The rate of ECC was subsequently analysed by using video playback.

In the first study 50 participants were randomised in blocks of five 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 100 bpm. Three pieces of music had a rate of 100 bpm and one much less than 100 bpm and another much faster than 100 bpm. In the second study 43 participants were randomised (in blocks of 10) to two groups: metronome group or “resuscitation clock” group. The metronome group listened to a minute of silence followed by two minutes of a recording of a metronome set to 100 bpm. 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 the 3, 6, 9, and 12 o'clock positions, respectively.

In the first study the rate of ECC was not statistically different between either the silence, music, or metronome groups (Freidman's test χ² = 3.6, p = 0.16; range 54–156, median 116 cpm). Those participants who had received formal CPR training within three months of taking part in the study did not have a statistically different rate of ECC compared with 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 with 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 100 bpm 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.