What should you do if you are not a health care professional and somebody collapses in the street and you feel no pulse? Should you do chest compressions, mouth-to-mouth, or both? Researchers from St. Louis, USA and Vienna, Austria are telling emergency services to advise lay bystanders not to bother with the mouth-to-mouth, and just focus on chest compressions until the ambulance or a health professionals arrive – their findings reveal that the patient has a better chance of survival this way. This study, published in the peer-reviewed medical journal The Lancet, provides yet more compelling evidence supporting the use of only chest-compressions if performed by a lay bystander in a non-hospital setting.
The investigators examined current evidence related to standard CPR (cardiopulmonary resuscitation) which includes mouth-to-mouth plus chest compressions, and chest-compressions only in a meta analysis*.
* A meta-analysis combines the results of several independent studies, usually from published literature – it is synthesized into summaries and conclusions which may be used to evaluate effectiveness, plan new studies, etc.
Part of their analysis included studying clinical trials involving randomly selected patients who received CPR either with or without mouth-to-mouth, according to dispatcher instructions. The second part of their study involved observing cohort studies of CPR. In all the studies, survival data was gathered. Their main focus was on survival to being discharged from hospital (what proportion of patients survived, and then went back home from hospital).
The initial analysis (primary meta-analysis) included information involving over 3,000 individuals who received CPR from lay bystanders in three randomized trials. The researchers found that:
- 14% of chest-compression only patients survived, compared to 12% who also received mouth-to-mouth
- This means a relative chance of survival increase of 22% if the bystanders omits the mouth-to-mouth part
- There was a 2.5% rise in the absolute increase in survival among patients who received chest-compression only CPR
- The 2.5% increase translates into 1 extra life saved for every 41 patients receiving chest-compression only CPR
The other analysis (secondary meta-analysis) did not include any randomized trials; there were seven observational cohort studies. Both groups, CPR with mouth-to-mouth and chest-compression only CPR gave identical survival rates – 8%. Dispatcher-assisted CPR was not covered in this study – the bystanders decided on their own what to do, without any instructions or advise from a dispatcher or health care professional via a telephone conversation, for example.
The researchers stress that in the first study, they had to combine data on all three trials in order to produce any significant differences between the outcomes of the two CPR techniques.
The authors wrote:
The fact that only three randomised trials have been done is testament to the difficulties associated with well designed prospective studies in this setting, such as obtaining of informed consent*, the little time available to randomise patients, adherence to the study protocol, tracking of patients and outcomes, and masking of investigators, study personnel, and patients from the allocated intervention. Because survival rates after out-of-hospital cardiac arrest are low and large treatment effects are unlikely, very large sample sizes are needed to show a significant survival benefit.
The researchers believe that for successful CPR the lay bystander should ensure there are “uninterrupeted chest compressions.”
Study authors, Dr Peter Nagele, Dr Michael Hüpfl and Dr Harald F Selig wrote:
By avoidance of rescue ventilations (mouth-to-mouth) during CPR, which are often fairly time-consuming for lay bystanders, a continuous uninterrupted coronary perfusion pressure is maintained, which increases the probability of a successful outcome.
When a patient’s heart stops (cardiac arrest), providing him/her with oxygen and ventilation during the initial minutes appears to matter less than effective chest compressions – there is usually enough oxygen within the patient’s body to keep him/her alive. Also, teaching chest-compression only results in better learning, there is less for the bystander to have to do and remember.
The authors conclude:
Our findings support the idea that emergency medical services dispatch should instruct bystanders to focus on chest-compression-only CPR in adults with out-of-hospital cardiac arrest.
Further studies are required which compare the results of lay bystander CPR techniques without dispatcher advice and with advice, the researchers added.
In an accompanying Comment in the same journal, Dr Jerry P Nolan, Royal United Hospital NHS Trust, Bath, UK, and Dr Jasmeet Soar, Southmead Hospital, North Bristol NHS Trust, Bristol, UK, wrote:
How should the results of these meta-analyses affect practice? If the information from a caller suggests sudden adult cardiac arrest, the dispatcher should provide instructions assertively on compression-only CPR. Thus the ‘kiss of life’ should be replaced by ‘Keep It Simple, Stupid’, which is broadly consistent with the practice of many emergency medical dispatchers in the UK. For adult primary cardiac arrest, dispatchers instruct the bystander to give 600 compressions (about 6 min) followed by two rescue breaths and then a compression:ventilation ratio of 100:2 until emergency medical personnel arrive.
The general role of bystander compression-only CPR is less clear. A bystander who starts CPR will not know how long the emergency medical services will take to arrive, and will not understand the difference between asphyxial and primary cardiac arrest. Therefore, ideally, lay people should continue to be trained in standard CPR. But any CPR is better than no CPR. Compression-only CPR has an important role in increasing the rate of bystander CPR by those who are untrained, who have only a minimum time for training, or who are unwilling or unable to provide rescue breathing.
Michael Hüpfl MD, Harald F Selig MD, Dr Peter Nagele MD
The Lancet, Early Online Publication, 15 October 2010
doi:10.1016/S0140-6736(10)61454-7
Written by Christian Nordqvist