a b s t r a c t

Aim: The aim of this study is to describe the outcome changes after out-of-hospital cardiac arrest (OHCA) in Gothenburg, Sweden, after introduction of mechanical chest compression (MCC).

Methods: Following introduction of MCC, 1183 OHCA patients were treated from November 1, 2007, to December 31, 2011 (period 2). They were compared with 1218 OHCA patients before MCC was introduced from January 1, 1998, to May 30, 2003 (period 1). Patients in period 2 were evaluated for survival in relation to MCC use.

Results: The percentage of patients admitted to hospital alive increased from 25.4% to 31.9% (P b .0001). Survival to 1 month increased from 7.1% to 10.7% (P = .002) from period 1 to period 2. The proportion of ventricular fibrillation/ventricular tachycardia decreased in period 2 (P = .002). However, bystander cardiopulmonary resuscitation (P b .0001), crew-witnessed cases (P = .04), percutaneous coronary intervention (P b .0001), therapeutic hypothermia (P b .0001), and Implantable cardioverter-defibrillator use (P = .01) increased, as did time from call to emergency medicine service arrival (P b .0001) and to defibrillation (P = .006).

In period 2, 60% of OHCA patients were treated with MCC. The percentages admitted alive to hospital (MCC vs no MCC) were 28.6% and 36.1% (P = .008). Corresponding figures for survival to 1 month were 5.6% and 17.6% (P b .0001). In the MCC group, we found increase in the delay from collapse to defibrillation (P b .0001), greater use of adrenaline (P b .0001), and fewer crew-witnessed cases (P b .0001).

Conclusion: Survival to 1 month after implementation of MCC was higher than before introduction. However, patients receiving MCC had low survival. Although case selection might play a role, results do not support a widespread use of MCC after OHCA.

(C) 2013

1. Background

The Chain of survival concept is the most well-developed idea in modern resuscitation after out-of-hospital cardiac arrest (OHCA) [1]. This field of knowledge is still expanding, and one of the new possible directions is the use of mechanical chest compression (MCC) [2]. In Gothenburg/Molndal, this has been used, at first in a study design [3] and thereafter as a regular part of the resuscitation equipment in some ambulances. The device that is used is the LUCAS from Jolife (Lund, Mechanical chest compression device“>Sweden). Our aims in this study were to describe the outcome after

? Conflict of interest: None of the authors has any conflicts to declare.

* Corresponding author. The Centre for Pre-hospital Care in Western Sweden, Prehospen, University of Boras and Sahlgrenska University Hospital, SE-413 45 Gothenburg, Sweden. Tel.: +46 31 342 1000; fax: +46 31 827375.

E-mail address: [email protected] (J. Herlitz).

OHCA in a well-defined region before and after the introduction of MCC and, furthermore, to describe survival in relation to the use of MCC.

1. Patients, methods, and definitions
   1. Design

This is a retrospective study based on data from the Swedish OHCA registry in the community of Gothenburg.

Mechanical chest compression device

The LUCAS device is a gas- or battery-driven cardiopulmonary resuscitation (CPR) device providing mechanical active compression- decompression CPR.

0735-6757/$ - see front matter (C) 2013 http://dx.doi.org/10.1016/j.ajem.2013.05.002

It has previously been shown to provide increased blood flow to the heart and brain in pig models [2,4] and to give higher end-tidal carbon dioxide levels in humans [5], improved metric changes in the electrocardiographic signal (which indicates a higher success rate after defibrillation) [6] and higher Quality of CPR before and during transportation [7] than regular CPR. The LUCAS device is safe to use in an out-of-hospital location [8] and appears to be associated with the same incidence and variety of injuries as manual CPR [9].

Patients

All consecutive cases of OHCA in Gothenburg/Molndal in which the emergency medical service (EMS) system attempted resuscitation between November 1, 2007, and December 31, 2011 (period 2), were followed up for 1-month survival. During this period, 1183 patients with OHCA were treated by the EMS in Gothenburg. Mechanical chest compression was used in 60% of the cases. These 1183 OHCA patients from period 2 were compared with 1218 OHCA patients from a period (period 1) before MCC was introduced. To obtain this sample, we had to include patients from January 1, 1998, to May 31, 2003. The period from June 1, 2003, to October 31, 2007, was deleted from this analysis because of (1) the performance of a cluster randomized intervention with MCC (3) and (2) the transition to the new Web-based OHCA registry. In the present analysis, data relating to postresuscitation care were collected from hospital records, and data on 1-month survival were obtained from death certificates. The data were transferred to a database following a formal protocol.

During study period 1 and 2, the inclusion criteria were all OHCA patients where CPR was attempted. There were no exclusion criteria.

Target area and population

Gothenburg is a city with an area of 448 km². In 2005, the resident population was 484940, of which 16% were 65 years or older. Molndal, which is a suburb of Gothenburg, has an area of 147 km², and in 2005, the resident population in Molndal was 57752. Gothenburg is more densely populated, with 1074 inhabitants per square kilometer, whereas the corresponding figure for Molndal is 393 inhabitants per square kilometer.

The average age in Molndal is 38.8 years, whereas it is 40.5 years in Gothenburg. In Gothenburg/Molndal, the average life span was 77 years for men and 82 years for women. Cardiovascular disease was the main cause of death (42%) [10].

Gothenburg/Molndal EMS system

unit is staffed by 1 experienced paramedic and 1 well-trained anesthesia nurse. Since 2009, this unit has been used for all priorities (1-3), which means that all the ambulance units in Gothenburg/Molndal now work on an equal basis in a 1-tier system.

The emergency dispatch center in Gothenburg

In Sweden, a person in distress dials 112 to contact the medical service. The dispatcher receiving the call interrogates the caller according to an existing national medical index. This index was introduced in 1998 and is based on symptoms and guides the dispatcher through the call with questions to ask, medical advice, for example, support in initiating telephone-CPR, to a priority and a categorization code (event codes). The event or symptoms give priority at 3 levels, where level 1 is the most urgent.

Statistical methods

In the evaluation of proportions, Fisher exact test was used. In the evaluation of continuous variables, the Mann-Whitney U test was used. In the multivariate analyses, logistic regression was used. All the factors that differed significantly between dead and alive in period 2 (P b .05) were included in the model.

P b .05 was regarded as significant. Two-tailed tests were used.

1. Results

This study comprises 2401 OHCA and stretches over a decade. This period is divided into 2 parts according to whether MCC was included in the ambulance equipment (November 1, 2007, to December 31, 2011) or not (January 1, 1998, to May 30, 2003).

Table 1

Patient characteristics, period 1 vs period 2

Period 1		Period 2		P
	n = 1218		n = 1183
Age (y; mean +- SD) (1157, 1150)a Sex (%) (1155, 1183) Female	68 +- 17 34		67 +- 18 37	.2 .10
Place (%) (1189, 1183)
At home Etiology (%) (1105, 1093) Cardiac	61 67		66 62	.01 .009
Initial rhythm (%) (1101, 1146) Ventricular fibrillation	32		26	.002
Witnessed status (%) (1114, 1134) Bystander witnessed	57		56	.77
Crew witnessed	13		17	.04
Bystander CPR (%) (903, 942) Yes	33		61	b.0001
MCC (%) (1218, 1170) Yes	0		60	b.0001
Treatment (%) (1218, 1169) Adrenaline	85		79	b .0001
Delay (median, min)

Until 2009, the ambulances in Gothenburg/Molndal were dis- patched according to a 2-tier system, that is, for each call judged to relate to a life-threatening state of health, 2 ambulances were simultaneously dispatched. In addition, 3 Advanced life support -equipped ambulances were available around the clock. All the ambulances are based at local fire stations both in Gothenburg and in Molndal. Since 2009, the ambulance trip sheet has been replaced by a computerized journal system. The EMS staff also have to fill in a national Resuscitation protocol for each patient with a cardiac arrest . The criterion for ceasing resuscitation “in the field” is asystole for more than 30 minutes, and this can only be judged by the nurse in the ALS unit.

• First tier, basic life support unit: an ambulance with 1 nurse (law since 2005) and 1 emergency medical technician on board. Nowadays, they are trained to give ALS but instructed only to defibrillate, when indicated, and perform CPR until the arrival of the second tier.
• Second tier (ALS unit): an ALS-equipped ambulance with the capacity to carry 1 patient treated by 3 members of staff. The ALS

Collapse to call for EMS (480, 463)^b

Call to arrival of EMS (958, 1,156)	5	9	b.0001
Collapse to defibrillation (169, 238)c	9	12	.006
Survival (%)
Hospitalized alive (1207, 1178)	25.4	31.9	b.0001
Survival to 1 mo (1212, 1175)	7.1	10.7	.002
Postresuscitation care (%)
PCI (319, 327)	7	26	b.0001
CABG (319, 327)	3	1	.13
Hypothermia (336, 327)	0	48	b.0001
ICD (318, 327)	3	8	.01
a Number of patients with information. b Only bystander-witnessed cases. c Witnessed and found in VF.

3 2 b.0001

There was no difference in terms of age, sex, or bystander-witnessed cases. The proportion of patients found in ventricular fibrillation (VF) and patients with a CA of cardiac etiology decreased during the second period (Table 1). However, the proportion of patients receiving bystander CPR, having their CA crew witnessed, or at home increased. When it comes to the delay from collapse to calling for the EMS, the time has decreased, whereas the delay from calling to the arrival

of the EMS and from collapse to defibrillation has increased.

Patients hospitalized alive and survival to 1 month increased during the second period.

Postresuscitation care became more intensified during the second period with regard to the use of percutaneous coronary intervention (PCI), therapeutic hypothermia, and implantable cardioverter-defi- brillator (ICD) (Table 2). In the second period, fewer patients were treated with adrenaline.

During the period, 60% received MCC. There was no difference in the location of CA, etiology, or VF as the initial rhythm. There were fewer women and fewer crew-witnessed cases in the MCC group. However, more patients had a bystander witnessing the CA and providing CPR in the MCC group.

In terms of delay, we found no difference in the time from collapse to call or from call to the arrival of the EMS, but there was an increase in the delay from collapse to defibrillation in the MCC group.

Survival to hospital admission and survival to 1 month were lower among the patients receiving MCC, as was the proportion receiving PCI, ICD, and coronary artery bypass graft (CABG). However, the proportion receiving therapeutic hypothermia was higher in the MCC group.

Table 3

Survival to 1 month (period 2)

Alive Dead P

	n = 126		n = 1049
Age (y; mean +- SD) (126, 1020)a	61 +- 18	67 +- 18		.0001
Sex (%) (126, 1049)
Female	21	39		b.0001
Place (%) (126, 1049)
At home	48	69		b.0001
Etiology (%) (120, 966)
Cardiac	74	60		.003
Initial rhythm (%) (119, 1018)
VF	75	20		b.0001
Witnessed status (%) (123, 1003)
Bystander witnessed	62	56		.21
Crew witnessed	30	15		b.0001
Bystander CPR (%) (123, 1003)
Yes	80	60		b.0001
MCC (%) (120, 1,042)
Yes	32	64		b.0001
Treatment (%) (120, 1042)
Adrenaline	42	83		b.0001
Delay (median, min) Collapse to call for EMS (64, 398)b	1	2		.03
Call to arrival of EMS (121, 1027)	7	9		.0001
Collapse to defibrillation (77, 160)c	8	14		b.0001
Postresuscitation care (%) (112, 212)
PCI	42.9	16.5		b.0001
CABG	4.5	0.5		.02
Hypothermia	52.7	46.2		.029
ICD	22.3	0.5		b.0001

The number of patients treated with adrenaline was higher in the group receiving MCC.

Among the survivors, we found a lower proportion of women, and the CAs were mostly bystander or crew witnessed, with the provision of early CPR (by the crew or a bystander). The mean age was 61 years.

Table 2

Characteristics in relation to MCC (period 2)

MCCa	Yes	No		P
	n = 705		n = 465
Age (y; mean +- SD) (687, 451)b	66 +- 17		67 +- 20	.02
Sex (%) (705, 465)
Female	34		42	.005
Place (%) (703, 464)
At home	67		65	.41
Etiology (%) (676, 405)
Cardiac	64		58	.07
Initial rhythm (%) (693, 440)
VF	26		25	.83
Witnessed status (%) (680, 438)
Bystander witnessed	60		50	b.0001
Crew witnessed	13		22	b.0001
Bystander CPR (%) (592, 341)
Yes	64		57	.04
Treatment (%) (701, 460)
Adrenaline	95		53	b.0001
Delay (median, min) Collapse to call for EMS (306, 150)c	2		2	.46
Call to arrival of EMS (691, 454)	9		9	0.41
Collapse to defibrillation (142, 86)d	14		8	b.0001
Survival (%)
Hospitalized alive (702, 463)	28.6		36.1	.008
Survival to 1 mo (702, 460)	5.6		17.6	b.0001
Postresuscitation care (%) (173, 147)
PCI	23.1		26.5	.51
CABG	0		4.1	.009
Hypothermia	60.1		36.1	b.0001
ICD	6.4		10.2	.22

^a Information missing on MCC in 13 patients.

^b Number of patients with information.

^c Only bystander-witnessed cases.

^d Witnessed and found in VF.

Information on survival was missing in 8 patients.

^a Number of patients with information.

^b Only bystander-witnessed cases.

^c Witnessed and found in VF.

Half the survivors were resuscitated in a public place; the majority had VF as the initial rhythm and had a CA of cardiac etiology. The delay from collapse to call, the arrival of the EMS, and to defibrillation was a median of 1, 2, and 6 minutes shorter among the survivors. The survivors were more frequently treated with post resuscitation care such as PCI, hypothermia, ICD, and CABG.

Multivariate analysis

We simultaneously considered the factors in Table 3 to find independent predictors of survival. The factors included in the model were age, sex, place (home), etiology (cardiac), initial rhythm (VF/ ventricular tachycardia [VT]), crew witnessed, early CPR (crew + bystander CPR), MCC, treatment (adrenaline), and time from call to arrival. The factors are listed in Table 4 in order of significance.

The chance of survival increased almost 20 times if the patient had VF/VT as the initial rhythm and 3 times if the CA was crew witnessed. Survival decreased with increasing age and an increased delay from call to EMS arrival. If the patients were treated with MCC or adrenaline, the chance of survival was half or less than half. Sex,

Table 4

Independent predictors of survival to 1 month (period 2)

	Odds ratio	(95% confidence intervals)
Agea	0.98	(0.96-0.99)
Initial rhythm (VF/VT)b	19.58	(11.08-36.42)
Witnessed status (Crew)b	2.92	(1.52-5.58)
Mechanical compressionb	0.50	(0.28-0.92)
Treatment (adrenaline)b	0.14	(0.08-0.26)
Delay (call to arrival of EMS)b	0.45	(0.28-0.72)
a Continuous, logarithmic scale.

^b Yes/no.

place (home), etiology (cardiac), and early CPR (bystander CPR or crew witnessed) were not found to be independent predictors of survival in the present analysis.

1. Discussion

A number of factors might explain the increase in survival that was found.

1. Community factors

The preparedness in the community for starting CPR among laypersons appears to have increased dramatically during the second period. This is best explained by the increasing number of educated rescuers. Today in Sweden, more than 2.5 million laypersons are educated in CPR [11,12]. Another finding that is possibly related to a better-educated society is the increase in crew-witnessed cases. People appear to call for the EMS more rapidly [13]. However, we did not find that early CPR was an independent predictor of survival to 1 month. The reason for this is not completely clear because, among the survivors, we found that most had either bystander CPR or were crew witnessed. Crew-witnessed OHCA was an independent factor for increased survival and might influence the association between early CPR and survival.

Emergency medicine service, dispatch, and time factors

Changes in the educational level of the EMS crew could also be a reason for increased survival. Since 2000, there has been a successive increase in the number of specially educated nurses, in favor of ambulance technicians, in the ambulance. Since 2005, the Swedish welfare system has made a minimum of 1 specially educated nurse in each ambulance in Sweden statutory.

The Ambulance response time increased by a median of 4 minutes between the 2 periods. One reason might be a change in the criteria for dispatch. Since the new index for dispatch was introduced, we have seen an increase in priority-2 calls (ambulance within 25 minutes) in favor of priority-3 calls (ambulance in 180 minutes) (Christer Axelsson; EMS statistics in Gothenburg). These changes have reduced the availability of ambulances. A deterioration in the traffic situation may also contribute to the increase in ambulance delay.

With every minute that passes after a CA, an increasing number of VFs have converted to a nonshockable rhythm [14], thereby explain- ing the observed decrease in VF.

This increase in delay corresponds well with the remaining part of Sweden [13]. Survival could have been even higher in period 2, if the EMS delay had remained unchanged.

Factors at resuscitation outside and inside hospital

Most survivors in the prehospital field are normally found among crew-witnessed cases [15] and patients with VF/VT [16]. This agrees with the present multivariate analysis finding that VF/VT and crew- witnessed cases were the strongest independent predictors of survival. However, in spite of increased survival in period 2, we found that VF/VT has decreased. This is contradictory, but both the present analysis and previous studies conducted in the same district

[17] indicate that the proportion of survivors among patients found in VF has increased over the years. The increase in patients hospitalized alive and short-term survival could indicate that patients in the VF/VT groups might receive better treatment both outside and inside hospital. One factor outside the hospital is the change in guidelines made in 2005, when immediate defibrillation was replaced by CPR for

2 minutes before defibrillation [18,19]. Furthermore, 2 important factors during period 2 were MCC, performing more effective chest

compressions than manual chest compressions made by the ambu- lance crew [5] as well as the increase in crew-witnessed cases [20].

During the second period, the patients hospitalized alive were also treated more aggressively with post resuscitation care, such as PCI, therapeutic hypothermia, and ICD. Previous studies suggest that postresuscitation care produces benefits and that the discharge rate from hospital, neurologic outcome, and 1-Year survival improve after the standardization of this link in the chain of survival [17,21-23]. The present result indicates that several factors inside and outside the hospital probably contribute to the increase in short-term survival.

Mechanical chest compression

During period 2, 60% of the patients received MCC. In this group, we found fewer women, fewer crew-witnessed CAs, and lower survival rates. In spite of this, a larger proportion of bystanders witnessed the CA, and there was a higher rate of bystander CPR. Most of the patients were treated with adrenaline, and the delay to defibrillation was 6 minutes longer in the MCC group. In all probability, patients who were rapidly defibrillated to a pulse- generating rhythm did not receive MCC.

The chance of survival was much lower when the patients received MCC. It is only possible to speculate about the reasons for low survival. Different aspects suggest that MCC targets a high-risk group with a lower chance of survival (fewer crew-witnessed cases and later defibrillation). These findings are in agreement with a previous study of the late start of MCC, a median of 18 minutes after CA [24]. The prehospital protocol always begins with manual chest compressions and defibrillation when possible or immediate defibrillation if the CA is crew witnessed. If the patient does not receive return of spontaneous circulation (ROSC), the next step is to apply the mechanical device and subsequently begin the treatment with intubation, an intravenous line and adrenaline. Most survivors during period 2 appear to have received ROSC at an early stage and did not require either mechanical compressions or adrenaline. The same observation was previously made by Holmberg et al [25] in relation to survival rates among OHCA patients requiring “late” interventions such as adrenaline or intubation. In the present analysis, the chance of survival was 1 of 10 if the patient was treated with adrenaline, and we found that 95% of the patients in the MCC group received adrenaline. The reason for not having mechanical compressions or adrenaline is probably early ROSC.

Evaluating the potential benefit of MCC could be difficult when low survival rates (3%-5% in this high-risk group) require a large sample size to reach a power of 80%. It is also possible to speculate about what MCC could possibly add to the existing prehospital protocol. As far as we know, chest compressions maintain the oxygenation more than starting a stationary heart. Perhaps we need to formulate a new prehospital protocol to use mechanical compressions as a bridge to further improve the treatment opportunity to restart a stationary heart. Many cases have already been reported, both from the prehospital field and from the catheterization laboratory [26-31]. Before the introduction of mechanical compressions, low-quality CPR during transport made transport to hospital impossible [32]. In Prague, a new hyperinvasive approach to OHCA is going to be tested in a new study protocol using mechanical compressions and cooling as a bridge to early invasive assessment at the hospital [33].

1. Conclusion

This survey describes OHCA during the last decade in the Municipality of Gothenburg/Molndal before and after the implemen- tation of MCC. One of the main aims was to evaluate whether MCC influenced survival. We observed an increase in the proportion of patients admitted alive to hospital as well as in the proportion of patients who were alive 1 month after OHCA. The proportion of VF/VT

among all patients with OHCA decreased during the period, but the proportion of survivors in the VF/VT group increased. This observation could be attributed to an increase in the proportion of crew-witnessed cases, but it might also be a result of the new Resuscitation guidelines that were implemented in 2006, which meant that many CAs received 2 minutes of CPR before defibrillation. Bystander CPR increased during the period, but it was not shown to be an independent predictor of survival. One disturbing factor that probably keeps the survival rates down is that the time from calling for an ambulance to EMS arrival increased by 4 minutes during this decade.

Inside the hospital, there have been tremendous developments in postresuscitation care. There has been an increase in the use of both PCI and therapeutic hypothermia. This treatment has probably had a positive impact on 1-month survival.

With regard to MCC, there are benefits for the EMS staff’s working environment, but we are unable to conclude that MCC contributed to the increase in survival. Like adrenaline, MCC appears to be used at a later stage in the treatment process and, therefore, targets a high-risk group with a lower chance of survival. Powering studies in high-risk groups with low survival requires huge samples. We need to think in a new way when it comes to analyzing interventions of this kind. Perhaps it would be possible to study MCC in a new optimized protocol in a subset of patients. The present analysis does not support a more widespread use of MCC after OHCA.

Acknowledgments

The study was supported by the Laerdal Foundation of Acute Medicine in Norway, OLA-foundation, Swedish Heart and Lung Foundation, and Jolife.

References

1. Cummins RO, Ornato JP, Thies WH, et al. Improving survival from sudden cardiac arrest: the “chain of survival” concept. A statement for health professionals from the Advanced Cardiac Life Support Subcommittee and the Emergency Cardiac Care Committee, American Heart Association. Circulation 1991;83:1832-47.
2. Steen S, Liao Q, Pierre L, et al. Evaluation of LUCAS, a new device for automatic mechanical compression and active decompression resuscitation. Resuscitation 2002;55:285-99.
3. Axelsson C, Nestin J, Svensson L, et al. clinical consequences of the introduction of mechanical chest compression in the EMS system for treatment of out-of-hospital cardiac arrest-a pilot study. Resuscitation 2006;71:47-55.
4. Rubertsson S, Karlsten R. Increased cortical cerebral blood flow with LUCAS; a new device for mechanical chest compressions compared to standard external compressions during experimental cardiopulmonary resuscitation. Resuscitation 2005;65:357-63.
5. Axelsson C, Karlsson T, Axelsson AB, et al. Mechanical active compression- decompression cardiopulmonary resuscitation (ACD-CPR) versus manual CPR according to pressure of end tidal carbon dioxide (P(ET)CO2) during CPR in out- of-hospital cardiac arrest (OHCA). Resuscitation 2009;80:1099-103.
6. Box MS, Watson JN, Addison PS, et al. Shock outcome prediction before and after CPR: a comparative study of manual and automated active compression- decompression CPR. Resuscitation 2008;78:265-74.
7. Olasveengen TM, Wik L, Steen PA. Quality of cardiopulmonary resuscitation before and during transport in out-of-hospital cardiac arrest. Resuscitation 2008;76: 185-90.
8. Steen S, Sjoberg T, Olsson P, et al. Treatment of out-of-hospital cardiac arrest with LUCAS, a new device for automatic mechanical compression and active decompression resuscitation. Resuscitation 2005;67:25-30.
9. Smekal D, Johansson J, Huzevka T, et al. No difference in autopsy detected injuries in cardiac arrest patients treated with manual chest compressions compared with

mechanical compressions with the LUCAS device-a pilot study. Resuscitation 2009;80:1104-7.

1. SCB: http://www.scb.se/default 30.aspx. In, Statistiska centralbyran.
2. Axelsson AB, Herlitz J, Holmberg S, et al. A nationwide survey of CPR training in Sweden: foreign born and unemployed are not reached by training programmes. Resuscitation 2006;70:90-7.
3. Stromsoe A, Andersson B, Ekstrom L, et al. Education in cardiopulmonary resuscitation in Sweden and its clinical consequences. Resuscitation 2010;81: 211-6.
4. Herlitz J. In: Herlitz J, editor. Swedish national registry of outside-hospital cardiac arrest. Goteborg; 2011.
5. Holmberg M, Holmberg S, Herlitz J. Incidence, duration and survival of ventricular fibrillation in out-of-hospital cardiac arrest patients in Sweden. Resuscitation 2000;44:7-17.
6. Axelsson C, Claesson A, Engdahl J, et al. Outcome after out-of-hospital cardiac arrest witnessed by EMS: changes over time and factors of importance for outcome in Sweden. Resuscitation 2012.
7. Herlitz J, Engdahl J, Svensson L, et al. Factors associated with an increased chance of survival among patients suffering from an out-of-hospital cardiac arrest in a national perspective in Sweden. Am Heart J 2005;149:61-6.
8. Martinell L, Larsson M, Bang A, et al. Survival in out-of-hospital cardiac arrest before and after use of advanced postresuscitation care: a survey focusing on incidence, patient characteristics, survival, and estimated cerebral function after postresuscitation care. Am J Emerg Med 2010;28:543-51.
9. Cobb LA, Fahrenbruch CE, Walsh TR, et al. Influence of cardiopulmonary resuscitation prior to defibrillation in patients with out-of-hospital ventricular fibrillation. JAMA 1999;281:1182-8.
10. Wik L, Hansen TB, Fylling F, et al. Delaying defibrillation to give basic cardiopulmonary resuscitation to patients with out-of-hospital ventricular fibrillation: a randomized trial. JAMA 2003;289:1389-95.
11. Hollenberg J, Herlitz J, Lindqvist J, et al. Improved survival after out-of-hospital cardiac arrest is associated with an increase in proportion of emergency crew- witnessed cases and bystander cardiopulmonary resuscitation. Circulation 2008;118:389-96.
12. Herlitz J, Castren M, Friberg H, et al. Post resuscitation care: what are the therapeutic alternatives and what do we know? Resuscitation 2006;69:15-22.
13. Sunde K, Pytte M, Jacobsen D, et al. Implementation of a standardised treatment protocol for post resuscitation care after out-of-hospital cardiac arrest. Resusci- tation 2007;73:29-39.
14. Tomte O, Andersen GO, Jacobsen D, et al. Strong and weak aspects of an established post-resuscitation treatment protocol-a five-year observational study. Resuscitation 2011;82:1186-93.
15. Axelsson C, Axelsson AB, Svensson L, et al. Characteristics and outcome among patients suffering from out-of-hospital cardiac arrest with the emphasis on availability for intervention trials. Resuscitation 2007;75:460-8.
16. Holmberg M, Holmberg S, Herlitz J. Low chance of survival among patients requiring adrenaline (epinephrine) or intubation after out-of-hospital cardiac arrest in Sweden. Resuscitation 2002;54:37-45.
17. Agostoni P, Cornelis K, Vermeersch P. Successful Percutaneous treatment of an intraprocedural left main Stent thrombosis with the support of an automatic mechanical chest compression device. Int J Cardiol 2008;124:e19-21.
18. Bonnemeier H, Olivecrona G, Simonis G, et al. Automated continuous chest compression for in-hospital cardiopulmonary resuscitation of patients with pulseless electrical activity: a report of five cases. Int J Cardiol 2009;136:e39-50.
19. Nielsen N, Sandhall L, Schersten F, et al. Successful resuscitation with mechanical CPR, therapeutic hypothermia and coronary intervention during manual CPR after out-of-hospital cardiac arrest. Resuscitation 2005;65:111-3.
20. Risom M, Jorgensen H, Rasmussen LS, et al. Resuscitation, prolonged cardiac arrest, and an automated chest compression device. J Emerg Med 2010;38:481-3.
21. Wagner H, Terkelsen CJ, Friberg H, et al. Cardiac arrest in the catheterisation laboratory: a 5-year experience of using mechanical chest compressions to facilitate PCI during prolonged resuscitation efforts. Resuscitation 2010;81:383-7.
22. Wik L, Kiil S. Use of an automatic mechanical chest compression device (LUCAS) as a bridge to establishing cardiopulmonary bypass for a patient with hypothermic cardiac arrest. Resuscitation 2005;66:391-4.
23. Sunde K, Wik L, Steen PA. Quality of mechanical, manual standard and active compression-decompression CPR on the arrest site and during transport in a manikin model. Resuscitation 1997;34:235-42.
24. Belohlavek J, Kucera K, Jarkovsky J, et al. Hyperinvasive approach to out-of hospital cardiac arrest using mechanical chest compression device, pre hospital intraarrest cooling, Extracorporeal life support and early invasive assessment compared to standard of care. A randomized parallel groups comparative study proposal. “Prague OHCA study”. J Transl Med 2012;10:163.