Friday October 15 2010
'Compression-only CPR' was compared to 'mouth-to-mouth' CPR
Several newspapers have today reported on resuscitation techniques after a new study analysed survival rates using the two main approaches. The Daily Telegraph suggested we should “skip the kiss” when giving the kiss of life, while BBC News emphasised that the study “backs chest compressions in resuscitation”.
The new study, which does not constitute official guidance, examined a form of CPR (cardiopulmonary resuscitation) that uses chest compressions but not breathing into the mouth. This is known as 'compression-only CPR'. It compared this technique to the standard, 'mouth-to-mouth' CPR in the specific setting of resuscitation for heart attacks outside of a hospital setting guided by emergency service personnel. Crucially, this means that the findings of this study only apply in these specific settings where bystanders are instructed by trained dispatchers in which technique to use.
An editorial in the same journal says that current practice is already broadly in line with these findings. Lay bystanders of a cardiac arrest who have received first aid training should not modify their approach on the basis of these findings.
Where did the story come from?
The study was carried out by researchers from the Medical University of Vienna and Washington University School of Medicine. It was funded by the US National Institutes of Health and the American Heart Association. The research was published in the peer-reviewed medical journal The Lancet.
There are some important caveats to be considered alongside these findings. Most of the papers do not detail the methods of this research well enough to make its limited applicability clear: the main conclusion of this study is that, in the specific event of out-of-hospital cardiac arrest of an adult, emergency service telephone dispatchers should focus on instructing bystanders on chest-compression-only CPR. The study cannot, and does not, make recommendations to ‘skip the kiss of life’ in unassisted CPR by a lay bystander who may or may not be trained.
The researchers also highlight in their discussion some circumstances where compression-only CPR is not appropriate, i.e. in cardiac arrest due to non-cardiac causes, such as from drowning. In light of this, the accompanying photograph featured in The Daily Telegraph's article - of CPR on a beach - may be particularly inappropriate.
Compression-only CPR would also not apply to most cases of cardiac arrest in babies and children because the cause is more likely to be due to asphyxia (such as drowning) rather than a cardiac cause (such as a heart attack).
What kind of research was this?
Members of the public are often required to resuscitate people who have had a heart attack until medical help arrives. Traditionally, this is through a method combining chest compressions and mouth-to-mouth ventilation, often under the remote telephone guidance of a member of the ambulance team, called a dispatcher. According to an editorial accompanying this research in The Lancet, survival rates after out-of-hospital heart attacks are 50% higher when dispatcher-assisted bystander CPR is used compared with cases where no CPR is given.
In this study, the researchers undertook a systematic review and meta-analysis to assess whether chest-compression-only CPR was any better than standard CPR in terms of survival of people who had an out-of-hospital heart attack.
What did the research involve?
The researchers searched a number of recognised literature sources for studies published between 1985 and 2010 that examined the differences between chest-compression-only CPR and standard techniques. A statistical technique called meta-analysis is often employed to combine the results of studies to provide a summary estimate.
The advantage of a meta-analysis is that it has greater statistical power than a single study because it adds together the participants from a number of studies. This makes it stronger and more likely to find a difference in treatment effects if one exists. Here, the researchers used meta-analysis to compare the effects of different CPR techniques.
The best ways to directly examine the effectiveness of a particular treatment is through randomised controlled trials (RCT). The researchers found three high-quality RCTs and seven observational studies of these CPR techniques. The RCTs were of similar design and they all compared dispatcher-assisted chest-compression-only CPR with dispatcher-assisted standard CPR techniques (i.e. including 'the kiss of life'). In these studies, telephone dispatchers randomly gave bystanders at the scene of a heart attack instructions in either of the two methods.
What were the basic results?
When the results of the three randomised controlled trials were combined, more of those receiving chest-compression-only CPR from bystanders survived compared with those receiving standard CPR. The chest-compression-only technique increased likelihood of survival by 1.22 times or 22% (RR 1.22, 95% CI 1.01 to 1.46).
In absolute terms, 2% more people survived when receiving chest-compression-only CPR than when receiving the standard method. When observational cohort studies were combined, there was no improvement in survival associated with this method of CPR.
How did the researchers interpret the results?
The researchers say that when instructing bystanders, emergency services dispatch staff should focus on chest-compression-only CPR for adults who have had out-of-hospital cardiac arrest.
This is an important study, and the researchers note that the best CPR technique for survival is a ‘controversial issue’ that has been discussed intensively over the past few years. They say that uninterrupted, high-quality chest compression is very important for successful CPR, and that these considerations were the reason why the 2005 resuscitation guidelines increased the recommended compressions-to-ventilations ratio (i.e. number of chest compressions in relation to number of rescue breaths) from 15:2 to 30:2.
While the difference in survival rates is relatively small (22%), it is still important, given the poor survival rates after out-of-hospital cardiac arrests.
There are some important points that affect how these findings should be interpreted by readers:
- The positive effects were for dispatcher-assisted chest-compression-only CPR, i.e. where bystanders were being instructed in the best way to do this by trained medical personal. The researchers do not advocate from their findings that people should make a deliberate decision to avoid mouth-to-mouth resuscitation without guidance from the emergency services. They specifically say that it is unclear whether chest-compression-only CPR should be recommended for unassisted lay bystander CPR.
- Importantly, all the incidents included in this study were of out-of-hospital cardiac arrest due to heart-related problems; the researchers say that other studies have found that standard CPR is better for cardiac arrest with non-cardiac causes (e.g. drowning, trauma and asphyxia, which would be the case in most arrests in babies and children).
- The publication of this study does not reflect any official change in CPR guidelines. However, the 2010 Resuscitation Guidelines by the UK Resuscitation Council is due to be published on Monday October 18, and may offer official guidance on the matter.
- An important weakness of the underlying research is that in the RCTs, the compression-to-ventilation ratio recommended in the standard CPR treatment was 15:2. Since then, official guidelines have recommended a ratio of 30:2, and studies that compare chest-compression-only with this more current standard CPR may have different results.
This well-conducted research has demonstrated an improvement in survival when dispatchers guide bystanders through chest-compression-only for the treatment of adults with an out-of-hospital cardiac arrest from cardiac causes. The findings only apply to this population in these specific circumstances, and do not apply to the general public in all circumstances.
The accompanying editorial to this article says that many emergency medical dispatchers in the UK make recommendations to bystanders of an adult cardiac arrest that are broadly consistent with these findings anyway. Specifically recommending 600 chest compressions (about 6 minutes) followed by two rescue breaths, then a compression: ventilation ratio of 100:2 until medical personnel arrive.
Behind the Headlines will cover any changes in official CPR guidelines when the 2010 Resuscitation Guidelines are published by the UK Resuscitation Council on Monday.