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Correspondence: Johan Herlitz, Professor of Acute Pre-hospital Care, The Centre for Pre-hospital Care in Western Sweden, Prehospen, University of Borås, Sweden, and Sahlgrenska University Hospital, Göteborg, Sweden.
In a review based on estimations and assumptions, to report the estimated number of survivors after out-of-hospital cardiac arrest (OHCA) in whom cardiopulmonary resuscitation (CPR) was started and to speculate about possible future improvements in Sweden.
An observational study.
All ambulance organisations in Sweden.
Patients included in the Swedish Cardiac Arrest Registry who suffered an OHCA between January 1, 2008 and December 31, 2010. Approximately 80% of OHCA cases in Sweden in which CPR was started are included.
In 11 005 patients, the 1-month survival rate was 9.4%. There are approximately 5000 OHCA cases annually in which CPR is started and 30-day survival is achieved in up to 500 patients yearly (6 per 100 000 inhabitants). Based on findings on survival in relation to the time to calling for the Emergency Medical Service (EMS) and the start of CPR and defibrillation, it was estimated that, if the delay from collapse to (i) calling EMS, (ii) the start of CPR, and (iii) the time to defibrillation were reduced to <2 min, <2 min, and <8 min, respectively, 300–400 additional lives could be saved.
Based on findings relating to the delay to calling for the EMS and the start of CPR and defibrillation, we speculate that 300–400 additional OHCA patients yearly (4 per 100 000 inhabitants) could be saved in Sweden.
In Europe, approximately 38 out-of-hospital cardiac arrests (OHCAs) per 100 000 inhabitants occur yearly that are treated by the Emergency Medical Service (EMS) , whereas the corresponding figure in the USA is 55 . A study of 10 medical centres in the USA and Canada reported that the overall survival (OS) rate among EMS-treated OHCA cases was 3–16% . A large variability in OS rate has also been reported in Europe ; however, a recent report suggested that an OS rate of 25% is possible if the cardiac arrest had a cardiac aetiology .
The Swedish Cardiac Arrest Registry (SCAR) was started in 1990 and tracks the incidence of OHCA, which reportedly has continuously increased. At the present time, all ambulance organisations in Sweden participate in the registry and local audits suggest that about 80% of all OHCA patients in whom cardiopulmonary resuscitation (CPR) is attempted are prospectively reported in the registry. It has been shown repeatedly that the most important factor in OS is the delay between collapse and the start of treatment [6-8]. However, other important aspects of OHCA treatment contribute to improved OS [9, 10], such as CPR quality and the hands-off interval (i.e. the time during which CPR is not performed) in association with defibrillation. If this interval can be reduced, it can be assumed that OS will further improve . Finally, the attitude among health-care providers to CPR in the pre-hospital setting might be of importance for OS after OHCA .
The number of patients receiving defibrillation prior to EMS arrival is increasing in Sweden due to the increased collaboration between the EMS and the fire and police departments. Furthermore, an increasing number of automated external defibrillators are being installed throughout the country . Another important component to improve OS rate following OHCA is the area of post-resuscitation care. It has been shown that a marked increase in the use of therapeutic hypothermia and percutaneous coronary intervention is associated with a marked increase in OS among patients who were brought alive to hospital after OHCA .
The hypothesis of this study is that OS can be improved by reducing the delay from collapse to calling the EMS to <2 min in all patients the delay from collapse to the start of CPR to <2 min in all patients and the delay from collapse to defibrillation to <8 min in all patients found in ventricular fibrillation. Thus, the aim of the present survey was to describe the number of OHCA patients who are successfully resuscitated in Sweden and estimate the number of lives that could be saved by reducing time delays to the start of treatment.
The present analyses included all OHCA patients reported to SCAR from January 1, 2008 to December 31, 2010. Sweden has an area of 449 964 km−2 and 9.45 million inhabitants as of 2011. We chose to analyse the period 2008–2010, as survival has increased during the past several years. The registry contains information regarding the type of initial rhythm, presumed aetiology, place of OHCA, whether bystanders initiated CPR prior to the arrival of the EMS, and time of collapse, call to the EMS, start of CPR, ECG recording, and defibrillation .
In 2010, the number of OHCA cases in Sweden was 4637 and the OS rate was 9.8%. The median delay from collapse to calling for the EMS was 2 min, while the delay from calling to the start of CPR was 3 min, and from calling to defibrillation, the delay was 12 min. However, the practicality of obtaining these goals will be discussed further in the discussion section.
A total of 11 005 OHCA cases were reported to the registry in 2008–2010. In Figs 1 and 2, the case outcomes are presented according to the Utstein Style Guidelines for Uniform Reporting of CPR attempts, which focuses on cases with a presumed cardiac aetiology (bystander witnessed and found in ventricular fibrillation).
Number of lives saved by reducing the delay in calling the EMS
Only bystander-witnessed cases (n = 2650; 53% of 5000) were analysed. Among them, the EMS was called >2 min after collapse in 1245 (47% of 2650) cases. As shown in Fig. 3, the OS rate was 13% if the delay to calling for the EMS was 0–2 min, whereas if the delay was >2 min, the mean OS rate was reduced to 6%. Based on these findings, it can be estimated that if all patients for whom the time to call the EMS was >2 min was reduced to 0–2 min after collapse, an additional 87 lives could be saved yearly in Sweden (OS rate at >2 min less OS rate at 0–2 min, 13–6% = 7% × 1245 = 87).
Number of saved lives by reducing time to CPR
All witnessed cases (by either bystanders or the EMS crew) were included in the analyses. In 52% of these patients, CPR was started >2 min after collapse. As shown in Fig. 4, the OS rate was 18% if CPR was started 0–2 min after collapse. If CPR was started >2 min after collapse, the mean OS rate was 6%. Based on these findings, it can be estimated that, if all patients in whom CPR was started >2 min after collapse was reduced to <2 min, an additional 218 lives could be saved.
Number of saved lives by reducing the time to defibrillation
All witnessed cases were included in the analysis. Among these patients, 33% were found in ventricular fibrillation, of which 69% were defibrillated >8 min after collapse. As shown in Fig. 5, when the time from collapse to defibrillation was 5–8 min, 43% of patients survived. Among the patients who were defibrillated >8 min after collapse, the mean OS rate was 18%. If all patients who were defibrillated >8 min after collapse were actually defibrillated within 5–8 min, an additional 199 lives could be saved.
Total number of saved lives
As shown in Table 1, a total of 504 lives can be saved by improving the time delays in the various links in the chain of survival. However, it can be assumed that there is an overlap in the separate links, thus the benefits from improvement in one link may be reflected in another. We project that the additional number of lives saved if the logistics were improved as suggested would be approximately 300–400, which is based on the hypothesis that delays to the start of CPR and defibrillation are independent of one another in principle. However, we must concede that a reduced delay period from collapse to calling for the EMS will be reflected in many cases in the delay to the start of CPR as well as the delay to defibrillation.
Table 1. The number of additional lives that might be saved outside of the hospital if logistics were improved (reduced delay)
Time from collapse to:
CPR, cardiopulmonary resuscitation.
Call (0–2 min)
CPR (0–2 min)
Defibrillation (5–8 min)
The main hypotheses raised by this review, based on estimations and assumptions, were: (1) during the course of 1 year, up to 500 OHCA patients (6 per 100 000 inhabitants) are currently successfully resuscitated in Sweden and (2) if the delays in the various links in the chain of survival could be improved, an additional 300–400 patients could be successfully resuscitated each year (4 per 100 000 inhabitants). This article thus highlights the fact that OHCA is a major public healthcare issue.
The Swedish Resuscitation Council has set a short-term goal to successfully resuscitate 1000 OHCA patients (11 per 100 000 inhabitants) yearly when CPR is attempted. As stated above, an improvement in logistics is only one of many aspects of CPR which have the potential to improve outcome. If we assume that about 1000 lives could be saved yearly, this corresponds to a survival rate of about 20%. Recently, Lindner et al.  reported an OS rate of 25% in Stavanger, Norway, for OHCA cases with a presumed cardiac aetiology and 48% for presumed cardiac aetiology among patients found in ventricular fibrillation. Although it is possible to speculate that such results can be achieved in less densely populated regions, recent data from Sweden do not indicate any association between regional population density and OS after OHCA .
Are our estimates realistic?
Delay to call the EMS
Within a 10-year perspective, it can be assumed that a call to the EMS will take place within 2 min after collapse with very few exceptions due to bystanders with cognitive dysfunction, immigrants who do not know the Swedish language, the lack of availability of a telephone, and unwitnessed incidences. In many cases, a call to 112 (the emergency call number in the European Union) will most likely take place within the first minute after collapse, which might further improve OS.
Delay to start of CPR
The number of bystander-witnessed cases in which CPR is started prior to the arrival of the EMS is continuously increasing in Sweden and now stands at almost 70% . Furthermore, in 15% of all OHCA cases, the cardiac arrest is witnessed by the EMS crew, thus CPR is started immediately . Within a 10-year perspective, the vast majority of patients with a witnessed OHCA will receive CPR within 2 min after collapse. Exceptions include the very elderly, bystanders with cognitive dysfunctions, and immigrants who do not know the Swedish language. However, many bystanders will start CPR within the first minute after collapse, which can likely further improve OS.
Delay to defibrillation
Even in a 10-year perspective, there will be patients who are not defibrillated within 8 min after collapse. However, there will also be patients who are defibrillated even more rapidly and in these patients, OS will increase still further. The estimation of the overall number of lives that could be saved in the future, if the delay to defibrillation were reduced appropriately, is therefore probably realistic. Based on these thoughts and the fact that there are countries in which the survival is well in line with the results which are expected to be found if our goals were achieved, we regard our calculations and assumptions as relatively plausible.
We only analysed witnessed cases, which comprise approximately 70% of all OHCAs in Sweden in which CPR is attempted, as the majority of survivors are found among witnessed cases . However, the interaction of the three links and the overall number of additional lives that could be saved due to improvements in logistics is not completely known, thus our conclusions are only rough estimates. There remains a missing rate of about 10%, i.e., those OHCA cases in which CPR was attempted, but were not reported to the registry at the time of OHCA or retrospectively. Among these cases, the delay to the start of treatment remains unknown. However, recent experiences do not indicate a marked difference between patients who are reported prospectively by the EMS staff and those that are not . For some variables recorded in the registry, information is missing in a number of patients, thus our data should be regarded as estimates. Finally, we cannot exclude the possibility of an association between age, co-morbidity, and delay to treatment. Patients who receive bystander CPR, and thereby receive CPR more rapidly, have been shown to be younger than those that do not . The strong association between delay to treatment and OS in OHCA  might therefore be slightly modified by age and co-morbidity. As a result, our calculations may be overly optimistic.
At present, about 500 patients (6 per 100 000 inhabitants) are resuscitated from OHCA in Sweden each year. If the delay to calling for the EMS, the start of CPR and defibrillation were reduced appropriately, we speculate that 300–400 additional lives (4 per 100 000 inhabitants) could be saved yearly in the future.