A BIT OF BIBLIOGRAPHY
In the previous article, I was wondering how I was going to teach children Basic Life Support (BLS) and how I was going to evaluate them. But first I had to… READ! Before me, what had been done? It was time to begin the bibliography work, and answer several questions:
– What do we know about BLS’ usefulness?
– What do we know about teaching BLS to the public?
– What do we know about teaching BLS to children?
– What do we know about using serious games for medical purposes?
Today we’ll try to answer the first question using 3 articles:
What do we know about the usefulness of basic life support?
A meta-analysis : « Predictors of survival from out-of-hospital cardiac arrest: a systematic review and meta-analysis », Sasson and al, Circulation, 2009
Link to the full text : http://circoutcomes.ahajournals.org/content/3/1/63.long
A meta-analysis is the highest proof level of medical studies. That’s why I’m going to explain this study in détails.
In this study the authors wanted to identify the key survival factors that influence survival of people suffering from a cardiac arrest out of a hospital. How did they do that?
– They searched all the online databases for all-over-the-world studies reporting cardiac arrests in adults between 1950 and 2008 (time of the study): 909 articles were identified.
– They selected, based on the titles and abstracts, the studies about cardiac-cause out-of-hospital cardiac arrest. They included only the studies were the survival was indicated: 204 were selected.
– A second analysis was done to identify only the well-conducted studies. There were 79, involving 142 740 patients in total.
– They extracted data about the management of these cardiac arrest and the survival of the patients, to determine the “weight” of each key factor in the survival rate.
The factors associated with a better survival were:
– Cardiac arrest witnessed by a bystander
– Cardiac arrest witnessed by emergency medical services
– Bystander’s BLS (from 3,9% to 16,1% survival)
– Ventricular fibrillation or ventricular tachycardia (=shockable rhythm)
– Return of spontaneous circulation
I selected this interesting figure for you:
Figure 5. Forest plot of studies reporting bystander CPR stratified by baseline survival.
This figure shows the Odds Ratios (OR) of Survival of the different studies, depending on bystanders’ CPR. The OR is like a comparison of chances. For example, if we look at the first study (Bachman), the OR is 3.18, which means that in this study, people had 3.18 more chance to survive if bystanders’ performed CPR on them than if they didn’t.
To help the reading of the figure, there is a line at “1”: all the point at the right of the line mean OR is bigger than 1, so CPR improved the survival of people in this study, all the points at the left mean CPR decreased the survival, and the points on the line mean it had no effect. As you can see, nearly all the points are in favour of bystanders’ CPR.
This kind of figure is quite striking when you want to show a lot of results!
What I think of this study
Internal validity = the study itself
This meta-analysis seems well done: the search was exhaustive, the majority of the studies were prospective cohort studies, which guarantee a good following of the patients and a good data collection.
External validity = the study among the literature
The pooled survival rate to hospital discharge was 7,6%, which is coherent with what we know of cardiac arrest nowadays (well, in fact, a meta-analysis is supposed to sum up the literature about a subject, so that’s not a real point😉 ).
So I think we can rely on this study.
What I learnt from this study
In 30 years, no big improvement in survival despite new drugs and in-hospital techniques: probably new efforts should focus on out-of-hospital care.
Among the out-of-hospital factors influencing survival, which one can we change?
– the presence of a bystander or emergency services at the moment of the cardiac arrest CAN’T be planned, of course
– we can’t change the fact that the cardiac rhythm is shockable or not, BUT we can teach bystanders how to use public external defibrillators
– we can’t plan the return of spontaneous circulation
So… the only thing we can IMPROVE is: the amount of bystanders implementing BLS (including the use of a defibrillator)
I’ll sum up a lot more for the 2 other studies, which also helped me a lot in the early stages of my project:
An observational study: “Characteristics and prognosis of sudden cardiac death in Greater Paris”, Bougouin W, Jouven X, Intensive Care Medicine, Mars 2014
Link to the full text: http://link.springer.com/article/10.1007%2Fs00134-014-3252-5
This study is an epidemiologic study. Its objective was to acquire recent data about sudden cardiac death in Greater Paris.
From May 2011 to May 2013, all sudden cardiac deaths occurring in adults in Paris and its suburbs were registered in the Sudden Death Expertise Center Registry, with information about demographics, pre-hospital care provided by bystanders or emergency medical services, use of defibrillation and drugs.
Then, if the patient was admitted to the hospital, all the cares he received were registered too. Finally, the evolution, complications, survival/cause of death were recorded.
6195 out-of-hospital cardiac arrests (OHCA) were recorded during the time of the study. Among them, 61,6% only had a resuscitation attempt by emergency medical services, and were included in the study.
Bystanders were present in 80% cases, bystanders’ CPR was performed in 45% cases. 65% victims died on site.
In multivariate analysis, bystander CPR (OR 2.1) and initial shockable rhythm (OR 11.5) remained positively associated with survival at discharge,
And another cool figure to illustrate that:
What I learnt from this study
This study shows basically the same thing as the meta-analysis, but it was done in our country, and more, in our city!
It was very important for me to know that were I intend to implement my experiment:
– there is also a lack of bystanders’ CPR
– bystanders’ CPR also improves the patients’ outcomes, even with the French health medical system (which include a physician in nearly every emergency medical services, unlike other countries)
And last but not least:
An interventional study: Dissemination of Chest Compression-Only Cardiopulmonary Resuscitation and Survival After Out-of-Hospital Cardiac Arrest, Iwami T, Kitamura T, Kiyohara K, Kawamura T, Circulation, 2015 Aug 4; 132(5):415-22
Link to the abstract: http://www.ncbi.nlm.nih.gov/pubmed/26048093
This study is a very interesting study that was conducted in Japan from 2005 to 2012. The authors wanted to estimate the survival of cardiac arrest victims according to the type of bystanders’ CPR they had received.
The authors recorded all the cardiac arrests in the whole country during all those years, and their outcomes.
A VERY interesting thing is that their main outcome was not only the survival, but the survival with favorable neurological outcome, a very relevant choice considering that during a cardiac arrest, the brain is the organ that suffers most from the circulation stop.
Among all the cardiac arrests witnessed by bystanders, 42,9% received CPR: among them, 30,6% received “chest compression only CPR” = just cardiac massage, no airway management, and 12,3¨% received “conventional CPR” = cardiac massage and lung insufflations.
The incidence of favorable neurological outcome increased over the years, in parallel with the dissemination of CPR and particularly chest compressions-only CPR in the country.
What I learnt from this study
Well this study is interesting because it shows us what can happen if we train an entire population to perform CPR: an increase in survival and neurological outcomes!
At this point, what do we get?
– bystanders’ CPR can save lives
– a lot of people don’t know how to perform it, or at least don’t do it
– chest compressions-only CPR is a good option for public training
More bibliography to come in another article! I’m waiting for your reviews!
And to thank you for reading this LOOOOONG article, a fun video to understand the “chest-compression only cardiopulmonary resuscitation”: