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Three Part Question

In [patients receiving external chest compressions in ED] is [a metronome better than no audible prompt] at [maintaining the quality of chest compressions delivered]?

Clinical Scenario

During a long resuscitation in the emergency department, you have to repeatedly remind the members of staff performing chest compressions to keep up a good rate. You recall that during previous cardiac arrests, the quality and rate of external cardiac compressions differs between operators. You wonder if a metronome could help providers by defining a set rate and so improve cardiopulmonary resuscitation (CPR) quality.

Search Strategy

Ovid MEDLINE(R) 1946 to November Week 3 2013: (Exp Cardiopulmonary Resuscitation/ OR cardiopulmonary resuscitation.af. OR cardiopulmonary.af. OR resuscitation.af. OR cpr.af.) AND metronome.af. Results limited to English language, adults and studies in humans. 17 records 0 new relevancies

The Cochrane Library Issue 12 of 12, December 2013: metronome:ti,ab,kw (Word variations have been searched) AND MeSH descriptor: [Cardiopulmonary Resuscitation] explode all trees 6 results 0 unique data.

Search Outcome

Seventeen papers were found, of which 11 appeared relevant from reviewing the abstract; subsequently, two were dismissed. A further 21 papers were identified by reference in the original 11 papers; subsequently eight were dismissed leaving a total of 21 relevant papers which are summarised in the following table.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Park et al 2013 Republic of Korea	67 Untrained laypeople performing compression only CRP on manikin with or without metronome.	Prospective randomised simulation study.	Compression rate and depth.	More accurate rate in metronome group (p<0.0001). Average compression depth equivalent in both groups but shallow compressions more common in metronome group (p=0.035).	Simulation so may not extrapolate to clinical care. Different chest compliance of manikin to human. Cohort of laypeople.
You et al 2013 Republic of Korea	30 Senior medical students performing compression only CRP on manikin with or without visual metronome in noisy environment.	Prospective randomised crossover simulation study.	Compression rate and depth.	More accurate rate in metronome group. No difference in compression depth.	Small study. Simulation so may not extrapolate to clinical care. Different chest compliance of manikin to human. Cohort of the clinically inexperienced students.
Lukas et al 2013 Germany	141 Senior medical students performing CPR with and without metronome.	Prospective randomised crossover simulation study.	Compression rate and depth.	More accurate rate in metronome group (p<0.005).	Simulation so may not extrapolate to clinical care. Different chest compliance of manikin to human. Cohort of the clinically inexperienced. Confounding factor of additional guidance feedback.
Chung et al 2012 Republic of Korea	64 Senior medical students performing 30:2 CPR on manikin with or without metronome.	Prospective randomised simulation study.	Compression rate and depth.	More accurate compression rate with metronome than without (p<0.001). Over first five cycles metronome group had lower average compression depth (p=0.028).	Single handed CPR. Simulation so may not extrapolate to clinical care. Different chest compliance of manikin to human. Cohort of the clinically inexperienced.
Chung et al 2013 Republic of Korea	27 Senior medical students.	Prospective randomised crossover simulation study.	Compression rate and depth.	Average compression depth increased with metronome rate (p<0.001). Average compression depth lower with metronome than without (p=0.007 at 100bpm).	Small study. Short periods of CPR (1 min). Simulation so may not extrapolate to clinical care. Different chest compliance of manikin to human.
Hafner et al 2012 U.S.A.	15 CPR trained doctors performing CPR with and then without music with 103 beats/min.	Prospective observational pilot study.	Compression rate.	Subjects felt CPR ability improved.	No baseline pre-musical metronome. Small study with weak methodology.
Paal et al 2012 Austria	141 Untrained laypeople performing CPR with or without guidance from a mobile phone including metronome.	Prospective randomised simulation study.	Various and compression rate.	More correct compression rates with metronome than without (p<0.001).	Simulation so may not extrapolate to clinical care. Different chest compliance of manikin to human. Cohort of the clinically inexperienced.
Hurst et al 2011 U.S.A.	40 Untrained laypeople performing 2 person CPR with or without metronome.	Prospective observational study.	Number of compressions and ventilations.	Greater accuracy of number of compressions with metronome than without (p<0.001).	Small study. Simulation so may not extrapolate to clinical care. Different chest compliance of manikin to human. Cohort of the clinically inexperienced.
Kern KB, et al. 2010 U.S.A.	34 pairs of CPR trained providers performing 30:2 CPR.	Prospective randomised simulation study.	Ventilations and compression rates.	Guideline rates achieved more with metronome than without (p<0.001).	Small study. Simulation so may not extrapolate to clinical care. Different chest compliance of manikin to human.
Havel et al 2010 Austria	24 ALS providers providing CPR in either ambulance vehicle or helicopter.	Prospective randomised crossover simulation study.	Compression rate and depth.	Guideline rates achieved more with metronome than without (p<0.0001). No significant difference in compression depth.	Small study. Simulation so may not extrapolate to clinical care. Different chest compliance of manikin to human.
Jäntti et al. 2009 Finland	44 ITU nurses performing 2 person 30:2 CPR.	Prospective crossover simulation study.	Compression rate and depth.	Guideline rates achieved more with metronome than without (p<0.001). No significant difference in compression depth.	Small study. Crossover not randomised. Simulation so may not extrapolate to clinical care. Different chest compliance of manikin to human.
Fletcher et al 2008 U.K.	314 Observation of chest compression rates from continuous pre-hospital ECG monitoring during introduction of metronome use.	Prospective observational study.	Compression rate.	Compression rate improved with introduction of metronome.	Broad observational study poorly controlled. Significant unrated variables.
Oh et al 2008 Republic of Korea	80 Senior medical & nursing students performing 2 person CRP with a definitive airway.	Prospective randomised simulation study.	Ventilations / compression rates and compression depth.	Ventilation and compression rates improved with metronome (p<0.01). Compression depth significantly decreased with metronome (p<0.01).	Simulation so may not extrapolate to clinical care. Study enacted post 8 hours of intensive CPR training. Different chest compliance of manikin to human.
Beckers et al 2007 Germany	202 First year medical students taught CPR with feedback device with metronome retested with or without the device(CPREzy™).	Prospective randomised simulation study.	Compression rate and depth.	Compression rate more accurate with metronome than without (p≤0.01).	Confounding factor of compression depth live feedback. Unusual and potentially confounding methodology, Simulation so may not extrapolate to clinical care. Cohort of the clinically inexperienced. Use of CRPezy device.
Noordergraaf et al 2006 Netherlands	224 Hospital employees performing only the compressions of 15:2 CPR with or without feedback device with metronome (CPREzy™).	Prospective randomised simulation study.	Compression rate and depth.	No significant difference in compression rate with metronome than without.	Participants self-assessed their skills as adequate. Simulation so may not extrapolate to clinical care. Different chest compliance of manikin to human. Use of CRPezy device.
Perkins et al 2004 U.K.	20 Medical students performing compression only CPR with or without feedback device with metronome (CPREzy™).	Prospective randomised crossover simulation study.	Compression rate and depth.	No significant difference in compression rate with metronome than without.	Simulation so may not extrapolate to clinical care. Different chest compliance of manikin to human. Cohort of the clinically inexperienced. Use of CRPezy device.
Chiang et al 2005 Taiwan	17 Patient’s real life resuscitations videoed then 13 Patient’s real life resuscitations with metronome videoed.	Prospective observational study.	Compression rate and others.	‘Significant’ improvement with metronome described in paper but unquantified.	No description of improvement in compression rate or statistical analysis Confounding factors of unblended study and education of resus team.
Williamson et al 2005 New Zealand	24 Untrained laypeople performing single person CPR with or without metronome before and after CPR training.	Prospective randomised simulation study.	Compression and ventilation rate.	Better compression (p=0.03) and ventilation (p=0.003) rates. No change in compression depth.	Simulation so may not extrapolate to clinical care. Cohort of the clinically inexperienced. Different chest compliance of manikin to human.
Boyle et al 2002 Australia	32 Hospital staff trained in CPR performing compression only CPR with or without metronome.	Prospective randomised simulation study.	Compression rate and depth.	Better compression rate with metronome (p<0.001).	Simulation so may not extrapolate to clinical care. Varied clinical skill of cohort. Different chest compliance of manikin to human. Use of CRPezy device.
Wik et al. 2001 Norway	24 Paramedic students training with and without metronome.	Prospective randomised crossover simulation study.	Compression rate and depth.	Improvement in all aspects when metronome introduced, no significant difference when removed.	More of training study. Simulation so may not extrapolate to clinical care. Different chest compliance of manikin to human.
Kern et al. 1992 U.S.A.	23 Adult intubated patients in cardiac arrest with or without metronome.	Prospective crossover study.	End tidal CO2.	Compressions at 120bpm produces better end-tidal CO2 than 80bpm (p<0.01). Compressions of either rate with metronome produce better end-tidal CO2 (p<0.01).	Small study. Difficulty of variable isolation given study design.

Comment(s)

The role of cardiopulmonary resuscitation, using closed-chest compressions and assisted or expired air ventilation, is to maintain cardiopulmonary perfusion while identifying then treating reversible causes of cardiopulmonary arrest. High-quality closed-chest compression (chest compression rate and depth) has been associated with increased survival. A large number of small studies suggest that using auditory feedback devices, such as metronomes, improve the rates of chest compression to rates closer to those recommended by the resuscitation council guidelines (100–120 compressions per minute for adults). For this reason resuscitation guidelines recommend mechanical devices to support rescuers providing chest compressions.

Metronomes are an option on some monitor/defibrillators. We focussed on the use of metronomes to guide closed-chest compressions as these are cheap, can be used from smart phone apps, and are placed on some defibrillators. We have identified some studies published subsequent to the publication of the most recent resuscitation guidelines. This is important, as the rate and depth of closed-chest compressions have changed during range time of the cited studies (eg, ALS 5th Edition: rate 100/min, depth 4–5 cm, ALS 6th Edition: rate 100–120/min, depth 5–6 cm) (Chung et al 2012, 2013). These studies add to the evidence that metronomes may assist in optimising chest compressions to optimum rates suggested by the guidelines. These studies involve a diverse range of participants from lay, medical student, nursing and medical backgrounds. The findings are consistent across all groups with metronome use being associated with faster, regular compressions. However, the increase in compression rate is offset by a fall in compression depth in some studies, particularly in non-medical participants. One study has specifically explored this and suggested that faster rates were associated with a reduction in the quality and depth of chest compressions (Hurst et al 2011). This is backed up by some evidence of a reduction in compression depth (Oh et al 2008, Chung et al 2012, Park et al 2013). The majority of studies have been performed in simulated clinical situations using manikins. Data from these studies may not translate to clinical scenarios. However, limited clinical observational data suggests similar findings do occur in the clinical arena. A high proportion of studies have been performed using the CPREzy device. No randomised clinical trials have been performed. However, given the consistency of evidence and the low risk of the intervention, a clinical randomised trial would be difficult to justify.

Clinical Bottom Line

The use of metronomes to guide the rate at which external chest compressions are delivered is associated with improved rates closer to those recommended in the current resuscitation guidelines.

References

1. Park SO, Hong CK, Shin DH et al. Efficacy of metronome sound guidance via a phone speaker during dispatcher-assisted compression-only cardiopulmonary resuscitation by an untrained layperson: a randomised controlled simulation study u Emerg Med J. 2013;30:657–61.
2. You JS, Chung SP, Chang CH et al. Effects of flashlight guidance on chest compression performance in cardiopulmonary resuscitation in a noisy environment. Emerg Med J. 2013;30:628–32.
3. Lukas RP, Engel P, Wecker S et al. Cardiopulmonary resuscitation guidance improves medical students' adherence to guidelines in simulated cardiac arrest: A prospective, randomised, cross-over study. Eur J Anaesthesiol. 2013;30:752–7.
4. Chung TN, Kim SW, You JS et al. The specific effect of metronome guidance on the quality of one-person cardiopulmonary resuscitation and rescuer fatigue J Emerg Med. 2012;43:1049–54.
5. Chung TN, Bae J, Kim EC et al, Induction of a shorter compression phase is correlated with a deeper chest compression during metronome-guided cardiopulmonary resuscitation: a manikin study. Emerg Med J. 2013;30:551–4.
6. Hafner JW, Sturgell JL, Matlock DL, et al. “Stayin’ alive”: a novel mental metronome to maintain compression rates in simulated cardiac arrests. J Emerg Med. 2012;43:e373–7.
7. Paal P, Pircher I, Baur T et al. Mobile phone-assisted basic life support augmented with a metronome. J Emerg Med. 2012;43:472–7.
8. Hurst VW 4th, Whittam SW, Austin PN et al. Cardiopulmonary resuscitation during spaceflight: examining the role of timing devices. Aviat Space Environ Med. 2011;82:810–13.
9. Kern KB, Stickney RE, Gallison L, Smith RE. Metronome improves compression and ventilation rates during CPR on a manikin in a randomized trial. Resuscitation 2010;81(2):206-10.
10. Havel C, Schreiber W, Trimmel H et al. Quality of closed chest compression on a manikin in ambulance vehicles and flying helicopters with a real time automated feedback. Resuscitation 2010;81:59-64.
11. Jäntti H, Silfvast T, Turpeinen A et al. Influence of chest compression rate guidance on the quality of cardiopulmonary resuscitation performed on manikins. Resuscitation 2009;80:453–7.
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13. Oh JH, Lee SJ, Kim SE et al. Effects of audio tone guidance on performance of CPR in simulated cardiac arrest with an advanced airway. Resuscitation 2008;79:273-7.
14. Beckers SK, Skorning MH, Fries M et al. CPREzy improves performance of external chest compressions in simulated cardiac arrest. Resuscitation 2007;72:100-7.
15. Noordergraaf GJ, Drinkwaard BW, van Berkom PF, et al. The quality of chest compressions by trained personnel: the effect of feedback, via the CPREzy, in a randomized controlled trial using a manikin model. Resuscitation 2006;69:241–52.
16. Perkins GD, Augré C, Rogers H et al. CPREzy: an evaluation during simulated cardiac arrest on a hospital bed. Resuscitation 2005;64:103–8.
17. Chiang WC, Chen WJ, Chen SY, et al. Better adherence to the guidelines during cardiopulmonary resuscitation through the provision of audio-prompts. Resuscitation 2005;64:297–301.
18. Williamson LJ, Larsen PD, Tzeng YC et al. Effect of automatic external defibrillator audio prompts on cardiopulmonary resuscitation performance. Emerg Med J. 2005;22:140–3.
19. Boyle AJ, Wilson AM, Connelly K et al. Improvement in timing and effectiveness of external cardiac compressions with a new non-invasive device: the CPR-Ezy. Resuscitation 2002;54:63–7.
20. Wik L, Thowsen J, Steen PA. An automated voice advisory manikin system for training in basic life support without an instructor. A novel approach to CPR training. Resuscitation 2001;50:167–72.
21. Kern KB, Sanders AB, Raife J et al. A study of chest compression rates during cardiopulmonary resuscitation in humans. The importance of rate-directed chest compressions. Arch Intern Med 1992;152:145–9.