a b s t r a c t

Objectives: To perform an updated meta-analysis of observational studies with unstratified cohort addressing whether compression-only cardiopulmonary resuscitation (CPR), compared with standard CPR, improves outcomes in adult patients with out-of-hospital cardiac arrest and a subgroup meta-analysis for the patients with cardiac etiology arrest.

Methods: We searched the relevant literature from MEDLINE and EMBASE databases. The baseline information and outcome data (survival to hospital discharge, favorable Neurologic outcome at hospital discharge, and return of spontaneous circulation on hospital arrival) were extracted both in an out-of-hospital cardiac arrest and Cardiac origin arrest subgroup. Meta-analyses were performed by using Review Manager 5.0.

Results: Eight studies involving 92 033 patients were eligible. Overall meta-analysis showed that standard CPR was associated with statistically improved survival to hospital discharge (risk ratio [RR], 0.95 [95% confidence interval, 0.91-0.99]) and return of spontaneous circulation on hospital arrival (RR, 0.95 [95% confidence interval, 0.92-0.99]) compared with compression-only CPR, but there is no significant difference in Favorable neurologic outcome at hospital discharge between 2 CPR methods (RR, 0.97 [95% confidence interval, 0.91-1.04]). In the subgroup of patients with a cardiac cause of arrest, the pooled meta-analysis found compression-only CPR resulted in the similar survival to hospital discharge as standard CPR (RR, 0.99 [95% confidence interval, 0.94-1.05]).

Conclusions: This meta-analysis found that compression-only CPR resulted in the similar survival rate as the standard CPR in the cardiac etiology subgroup. It is unclear for the patients with noncardiac cause of arrest and with long periods of untreated arrest.

(C) 2014

Introduction

Out-of-hospital cardiac arrest is still a considerable public health issue [1]. The incidence of out-of-hospital cardiac arrest is estimated to be 213.1 per 1 000 000 population [2]. Good-quality and high-incidence of bystander cardiopulmonary resuscitation (CPR) can increase the chance of survival in out-of-hospital cardiac arrest [3,4]. Despite huge efforts to improve the effectiveness of bystander CPR over the past decades, the survival rate of bystander CPR remains low and there are always some controversial comments on the CPR method for bystander CPR [3,5]. Several randomized clinic studies showed that dispatcher- assisted compression-only CPR led to better survival rate than standard

* Corresponding author. Department of Emergency Medicine, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510120, China. Tel.: +86 20 81332469;

fax: +86 20 81332650.

E-mail address: [email protected] (Z. Huang).

CPR, although the difference was not statistically significant [6-8]. A meta-analysis study including only randomized controlled trials also found that compression-only CPR was significantly associated with improved survival rate to discharge compared with standard CPR [9,10]. In contrast, another meta-analysis of observation studies showed that there was no significant difference in survival between the 2 CPR methods [10]. Furthermore, a large-scale prospective study indicated that for patients with arrest due to noncardiac causes, standard CPR may actually have better benefits in survival rate than compression-only CPR [11]. At the same time, a single randomized clinic study and a large-scale observational study both found that compression-only CPR resulted in better outcomes compared with standard CPR in a cardiac origin arrest subgroup [8,12]. Hence, it was indicated that the stratified analysis of out-of-hospital cardiac arrest may be more reasonable and should be performed for the comparison of compression-only CPR and standard CPR. Because cardiac diseases are the most frequent cause of out-of- hospital cardiac arrest, we supposed that compression-only CPR may be more effective in patients with a cardiac cause of arrest. Previous meta-

http://dx.doi.org/10.1016/j.ajem.2014.01.055 0735-6757/(C) 2014

analyses did not conduct the analysis of cardiac origin arrest subgroup. Several new observational studies with stratified analysis have emerged [12,13]. Therefore, we performed an updated meta-analysis of observa- tional studies with unstratified cohort addressing whether compression- only CPR, compared with standard CPR, improves outcomes in adult patients with out-of-hospital cardiac arrest and a subgroup meta- analysis for the patients with cardiac etiology arrest.

Methods

The study was performed in accordance with the guidelines from the Meta-analysis Of Observational Studies in Epidemiology group [14].

Literature search

Two authors independently retrieved observational studies that compared compression-only CPR and standard CPR from MEDLINE and EMBASE databases between January 1, 1990, and October 1, 2013. The search terms included “chest compression-only,” “compression alone,” “hands-only,” “bystander CPR,” “standard CPR,” and “out-of- hospital cardiac arrest.” The search strategy is presented in Appendix

A. In addition, we also reviewed the reference of retrieved articles for additional pertinent studies. We placed no language restrictions on the searches.

Full-text articles assessed for eligibility

n = 51

Articles excluded based on title and abstract

n = 821

Potentially relevant articles in the initial literature search

n = 872

Inclusion and exclusion criteria

Two authors independently screened the full texts of eligible articles according to inclusion and exclusion criteria. For inclusion, studies had to meet the following criteria: (1) observational clinic studies, (2) com- parison of chest compression-only vs standard CPR, (3) out-of-hospital arrest, and (4) survival rate, return of spontaneous circulation (ROSC), or neurologic outcome data available. We excluded studies if they met the following exclusion criteria: (1) any other intervention (eg, public education plan), (2) duplicate publication and data, (3) only just for arrests of noncardiac origin, and (4) only just for children or old people.

Data extraction

The baseline information was extracted from each study by 3 reviewers independently. We also obtained the following outcome data: survival to hospital discharge, favorable neurologic outcome at hospital discharge, and ROSC on hospital arrival. We considered 30-day survival data as survival rate to hospital discharge if the latter was not available, seeing that the 2 kinds of outcome nearly had the same data in some relevant studies [15]. We also used the rate of consciousness 14 days after CPR instead of survival data to hospital discharge when the information was unavailable [16]. Favorable neurologic outcome was defined as a Glasgow-Pittsburgh cerebral-performance category of 1 or 2 on a 5-category scale [17]. Meanwhile, these outcome data in the subgroup of patients with a cardiac cause of arrest were extracted from

Observational studies included in the meta-analysis

n = 8

(n = 3 with survival data of the cardiac etiology subgroup)

Articles excluded according to inclusion and exclusion criteria

n = 43

Reasons for exclusion

not observational clinic studies n = 19

reviews n = 5 duplicate data n = 2

with any intervention n = 1 just for arrests of non-cardiac origin n = 3

just only for children or old people n = 5

Fig. 1. Flowchart representing the Selection process.

selected articles. The cardiac origin arrest subgroup include the patients whose arrest was presumed to be of cardiac origin, unless it was known to be caused by trauma, hanging, drowning, drug overdose, asphyxia, or any other noncardiac causes [12,18].

Statistical analysis

Meta-analyses were performed by using Review Manager 5.0 (the Cochrane Information Management System, http://ims.cochrane.org/ revman). Risk ratios (RRs) and 95% confidence intervals were calculated and pooled in both a fixed-effects model and a random-effects model, which was used to control for heterogeneity [19]. The quality of each study was assessed independently by 2 authors with the Newcastle- Ottawa Scale [20]. Besides the primary meta-analysis with an unstratified cohort in out-of-hospital cardiac arrest, a subgroup meta-analysis for the patients with cardiac etiology arrest was performed. We examined for potential publication bias with funnel plots. The heterogeneity among studies was assessed by the Cochran Q and I² statistics. Sensitivity analyses were performed by using random-effect methods.

Results

Search results

A total of 872 relevant citations were ascertained from the initial literature search. Eight hundred twenty-one articles were excluded based on title and abstract. According to inclusion and exclusion criteria, 2 authors assessed the full text of remained articles and excluded 43 articles. In the final analysis, 8 articles totally were included [12,16-18,21-24] (Fig. 1).

Study characteristics

Baseline information of the 8 Observational cohort studies including author’s last name, year of publication, country of population studies, numbers of survivors in different groups, and so on (Table 1). All eligible studies included 54 018 patients with compression-only CPR and 38 015 patients with standard CPR. Of the 8 studies, 3 articles provided survival rates in the subgroup of patients with a cardiac cause of arrest. The quality of these studies was high (Table 2).

Data and statistical analysis

Most of these observational studies found that there was no significant difference in survival between the compression-only CPR group and the standard CPR group, but overall meta-analysis showed that standard CPR was associated with statistically improved survival data to hospital discharge compared with compression-only CPR (RR, 0.95 [95% confidence interval, 0.91-0.99]; Fig. 2). Standard CPR was also associated with a statistically improved ROSC on hospital arrival (RR, 0.95 [95% confidence interval, 0.92-0.99]; Fig. 3). However, after pooling 4 studies referring to neurologic outcome in a meta-analysis, it showed no difference in favorable neurologic outcome at hospital discharge between the compression-only CPR group and the standard CPR group (RR, 0.97 [95% confidence interval, 0.91-1.04]; Fig. 4). The heterogeneity among these studies was nearly neglected (I² = 0).

In the subgroup of patients with a cardiac cause of arrest, the pooled meta-analysis found that there was no significant difference in survival rate to hospital discharge (RR, 0.99 [95% confidence interval, 0.94-1.05]) with no evidence of heterogeneity as indicated by an I² of 0 (Fig. 5). However, only the study in 2013 referred to neurologic outcome and considered compression-only CPR led to better 30-day favorable neurologic outcome than standard CPR in the subgroup with cardiac etiology [12].

Overall funnel plots were not suggestive for publication bias (Fig. 6). Sensitivity analyses using random-effect methods identified similar results.

Discussion

In this meta-analysis of 90 706 patients from 7 observational studies with unstratified cohort, we found that standard CPR could lead to better outcome of survival and ROSC than compression-only CPR, but there is no significant difference in favorable neurologic outcome at hospital discharge between the 2 CPR methods. However, some previous meta- analysis studies suggested that compression-only CPR was associated with improved survival rate compared with standard CPR [9,10]. Several reasons could explain this controversy. First, each of the randomized studies in the previous meta-analysis just compares dispatcher-assisted standard CPR with compression-only CPR [6-8]. However, these observational studies included in this meta-analysis focus on

Table 1

Characteristics of the studies included in the meta-analysis

Articles

Location,

Compression

Standard

ROSC on hospital arrival

Survival to hospital discharge/30 d

Favorable neurologic

period

only CPR

CPR

outcome at hospital

discharge/30 d

Compression- Standard

Compression- Standard

Compression- Standard

only CPR CPR

only CPR CPR

only CPR CPR

Van Hoeyweghen et al [16]b

Belgium, NA

263

443

26/263 71/443

Waalewijn et al

Amsterdam, 1995-

41

437

13/41

144/437

6/41

61/437

[21]

1997

SOS-Kanto study group [18]a Bohm et al [23]a

Kanto, 2002-2003 Swedish, 1990-2005

439 1145

712 8209

229/1145

1609/8209

38/439 77/1145

58/712 591/8209

27/439

30/712

Iwami et al [22]a

Osaka, 1998-2003

544

783

37/544 (cardiac

60/783 (cardiac

etiology subgroup)

etiology subgroup)

Olasveengen

Oslo, 2003-2006

145

281

42/145

90/281

15/145

35/281

14/145

27/281

et al [24]

Ong et al [15] Singapore, 2001-

154

287

12/154

30/287

4/154

8/287

2/154

6/287

2004

3/120 (cardiac etiology subgroup)

5/202 (cardiac etiology subgroup)

4379/51 286 2407/26 863 2218/51 267 1205/26

JCS-ReSS	Japan, 2006-2010	51 285	26 864	6022/51 286	3328/26
Group [12]a	864

3106/29 572 (cardiac etiology subgroup)

1671/15 826 (cardiac etiology subgroup)

845

^a In these studies, we considered 30-day survival data as survival rate to hospital discharge because the latter was not available.

^b In the study, we used the rate of consciousness 14 days after CPR instead of survival data to hospital discharge because the latter was not available.

investigating the outcome between the compression-only CPR group and the standard CPR group, not restricted in dispatcher-assisted bystander CPR. The incidence of bystander-initiated CPR as a more common method affects the outcome of Pooled analysis. In the Japanese study, it found that dispatcher-assisted CPR was associated with better Short-term outcome than bystander-initiated CPR, and compression- only CPR had the same benefits compared with standard CPR [12]. Also, this study suggested that, like some previous meta-analysis studies, dispatcher-assisted compression-only CPR should be recommend in out- of-hospital cardiac arrest in adults. Furthermore, it showed that dispatcher-assisted CPR contributed to the benefits of compression- only CPR [12]. However, other studies that just only included dispatcher- unassisted bystanders found that no significant difference was seen in short-term outcome between the compression-only CPR group and the standard CPR group [15,22]. It is likely that CPR with dispatcher assist or not is an important factor, which would affect the outcome of comparison between compression-only CPR and standard CPR. Howev- er, there are few studies that considered this influencing factor and conducted the related stratified analysis. Second, both the previous and the present meta-analysis studies investigate the overall outcome of out- of-hospital cardiac arrest. However, for the patients with noncardiac cause of arrest, rescue breathing is an important element of successful resuscitation stated by the American Heart Association guidelines [2]. Furthermore, the Nationwide observational study by Kitamura et al [11] indicated that standard CPR (chest compressions plus Rescue breathing) had a significant benefit in survival rates and neurologic outcome for out-of-hospital cardiac arrest of Noncardiac etiology. The proportion of patients with noncardiac etiology arrest may have an evidently impact on overall survival rates of out-of-hospital cardiac arrest. The results stratified by cause of arrest may be more convincing. Third, the time interval between collapse and first bystander CPR is very important for survival rates of out-of-hospital cardiac arrest. For the patients with the prolonged duration of arrest, rescue breathing may improve outcomes of out-of-hospital cardiac arrest [25]. The study by the SOS-KANTO study group identified that compression-only CPR resulted in a higher rate of favourable neurologic outcome than standard CPR for the patients with resuscitation starting within 4 minutes of collapse, but not for the patients with resuscitation delayed for 4 minutes from collapse [18]. However, most randomized and observational articles did not perform the comparison of the time-dependent effectiveness between the compression-only CPR and the standard CPR [18,21]. This unstratified analysis also affects the results of meta-analysis.

Table 2

Quality assessment (Newcastle-Ottawa Scale) of the studies included in the meta-analysis

Compatibility 1A

*

*

*

*

*

*

*

*

Outcome 1A

*

*

*

*

*

*

*

*

Total scores

3A

*

*

*

*

*

*

*

*

3B

4

*

*

*

*

*

*

*

*

1B

1B

2A

*

*

*

*

*

*

*

*

3A

*

*

*

3B

8

9

9

9

9

9

8

9

*

*

*

*

*

*

*

*

*

*

*

Each one symbol asterisk indicated that the article met the corresponding requirement and scored 1 point.

The cardiac etiology subgroup analysis of this study showed that

compression-only CPR resulted in the similar survival to hospital discharge as standard CPR. An estimate of the difference in 30-day favorable neurologic outcome between compression-only CPR and standard CPR could not be done with certainty because only one observational study conducted it and suggested that compression-only CPR led to better 30-day favorable neurologic outcome than standard CPR in the subgroup with cardiac etiology arrest. These results indirectly enforce the importance of chest compression in resuscitation of the patients with cardiac etiology arrest. The American Heart Association guidelines also stated that it was important for successful resuscitation to minimize the interruption of chest compression [2]. Furthermore, one randomized study demonstrated compression-only CPR resulted in a higher proportion of patients surviving to hospital discharge for patients with a cardiac cause of arrest compared with the standard CPR, not for overall patient with out-of-hospital cardiac arrest [8]. Besides that, there are more patients with compression-only CPR (54 018) than standard CPR (38 015) in the meta-analysis including 8 observational studies. It may indicate that the compression-only CPR is more likely to be accepted by bystanders [12,26]. Maybe it can improve the incidence of bystander CPR and lead to more benefits for patients with out-of-hospital cardiac arrest. This study has some limitations. One is that this study did not adjust the final data for characteristics of the resuscitation episode just like age, location, race, and so on. Some studies included in the meta-analysis

Studies

Selection 1A

*

*

*

*

*

*

*

*

1B

2

*

*

*

*

*

*

*

*

Van Hoeyweghen et al [16] Waalewijn et al [21]

SOS-Kanto Study Group [18] Bohm et al [23]

Iwami et al [22] Olasveengen et al [24] Ong et al [15]

JCS-ReSS Group [12]

compression-only CPR standard CPR Risk Ratio Risk Ratio

M-H, Fixed, 95% CI

Study or Subgroup	Events	Total	Events	Total	Weight	M-H, Fixed, 95% CI	Year
Van Hoeyweghen 1993	26	264	71	443	1.5%	0.61 [0.40, 0.94]	1993
Waalewijn 2001	6	41	61	437	0.3%	1.05 [0.48, 2.28]	2001
SOS-Kanto group 2007	38	439	58	712	1.3%	1.06 [0.72, 1.57]	2007
Bohm 2007	77	1145	591	8209	4.2%	0.93 [0.74, 1.17]	2007
olasveengen 2008	15	145	35	281	0.7%	0.83 [0.47, 1.47]	2008
Ong 2008	4	154	8	287	0.2%	0.93 [0.29, 3.05]	2008
JCS-ReSS Group 2013	4379	51286	2407	26863	91.8%	0.95 [0.91, 1.00]	2013
Total (95% CI)		53474		37232	100.0%	0.95 [0.91, 0.99]
Total events	4545		3231

Heterogeneity: Chi2 = 4.70, df = 6 (P = 0.58); I2 = 0% Test for overall effect: Z = 2.31 (P = 0.02)

0.5 0.7 1 1.5 2

compreesion-only CPR standard CPR

Fig. 2. Forest plot of RR for survival to hospital discharge in out-of-hospital cardiac arrest.

compression-only CPR standard CPR Risk Ratio Risk Ratio

Study or Subgroup	Events	Total	Events	Total	Weight	M-H, Fixed, 95% CI	Year	M-H, Fixed, 95% CI
Waalewijn 2001	13	41	144	437	0.5%	0.96 [0.60, 1.54]	2001
Bohm 2007	229	1145	1609	8209	8.1%	1.02 [0.90, 1.15]	2007
olasveengen 2008	42	145	90	281	1.3%	0.90 [0.67, 1.23]	2008
Ong 2008	12	154	30	287	0.4%	0.75 [0.39, 1.41]	2008
JCS-ReSS Group 2013	6022	51286	3328	26864	89.7%	0.95 [0.91, 0.99]	2013
Total (95% CI)		52771		36078	100.0%	0.95 [0.92, 0.99]
Total events	6318		5201

Heterogeneity: Chi2 = 1.92, df = 4 (P = 0.75); I2 = 0% Test for overall effect: Z = 2.56 (P = 0.01)

0.5 0.7 1 1.5 2

compreesion-only CPR standard CPR

Fig. 3. Forest plot of RR for ROSC on hospital arrival in out-of-hospital cardiac arrest.

compression-only CPR standard CPR Risk Ratio Risk Ratio

Study or Subgroup	Events	Total	Events	Total	Weight	M-H, Fixed, 95% CI	Year	M-H, Fixed, 95% CI
SOS-Kanto group 2007	27	439	30	712	1.4%	1.46 [0.88, 2.42]	2007
Ong 2008	2	154	6	287	0.3%	0.62 [0.13, 3.04]	2008
olasveengen 2008	14	145	27	281	1.1%	1.00 [0.54, 1.86]	2008
JCS-ReSS Group 2013	2218	51267	1205	26845	97.2%	0.96 [0.90, 1.03]	2013
Total (95% CI)		52005		28125	100.0%	0.97 [0.91, 1.04]
Total events	2261		1268

Heterogeneity: Chi2 = 2.85, df = 3 (P = 0.41); I2 = 0% Test for overall effect: Z = 0.87 (P = 0.38)

0.2 0.5 1 2 5

compreesion-only CPR standard CPR

Fig. 4. Forest plot of RR for favorable neurologic outcome at hospital discharge in out-of-hospital cardiac arrest.

compression-only CPR standard CPR Risk Ratio Risk Ratio

Study or Subgroup

Events

Total

Events

Total

Weight

M-H, Fixed, 95% CI

M-H, Fixed, 95% CI

Iwami 2007

37

544

60

783

2.2%

0.89 [0.60, 1.32]

JCS-ReSS Group 2013

Ong 2008

Total (95% CI)

Total events

3106

3

3146

29572

120

30236

1671

5

1736

15826

202

16811

97.6%

0.2%

100.0%

0.99 [0.94, 1.05]

1.01 [0.25, 4.15]

0.99 [0.94, 1.05]

Heterogeneity: Chi2 = 0.31, df = 2 (P = 0.85); I2 = 0%

Test for overall effect: Z = 0.27 (P = 0.79)

0.5 0.7 1 1.5 2

compreesion-only CPR standard CPR

Fig. 5. Forest plot of RR for survival to hospital discharge in cardiac origin arrest subgroup.

Fig. 6. Funnel plot of the meta-analysis. A, Survival to hospital discharge in out-of-hospital cardiac arrest. B, ROSC on hospital arrival in out-of-hospital cardiac arrest. C, Favorable neurologic outcome at hospital discharge in out-of-hospital cardiac arrest. D, Survival to hospital discharge in cardiac origin arrest subgroup.

have done this adjustment and avoid the bias [12,15]. However, for our study, it is difficult to get enough information to control these factors and bias from all of the included studies. Another limitation is that the ratios of compression to ventilation are different among the included studies because of the updating CPR guideline, which increasingly supports and stresses the importance of chest compression. It may bring some invisible benefit to compression-only CPR.

In conclusion, this study found that compression-only CPR resulted in the similar survival rate as standard CPR in the cardiac etiology subgroup. Considering its possibly higher acceptance rate and easier performance, compression-only CPR should be recommended to bystander for patients with a cardiac cause of out-of-hospital arrest. It also should be considered that compression-only CPR with dispatcher assist may lead to better outcomes for those patients. However, it is unclear for the patients with noncardiac cause of arrest and with long periods of untreated arrest.

Appendix A. Search strategy used for the literature search in MEDLINE and EMBASE

Each search used a combination of free text and subject headings. #1 bystander CPR OR bystander cardiopulmonary resuscitation #2 bystander AND cardiopulmonary resuscitation

#3 lay rescuer AND cardiopulmonary resuscitation #4 bystander AND resuscitation

#5 lay rescuer AND resuscitation #6 #1 OR #2 OR #3 OR #4 OR #5

#7 chest compression-only OR chest compression only #8 compression alone OR compression only

#9 hands-only

#10 #7 OR #8 OR #9

#11 standard CPR OR standard cardiopulmonary resuscitation #12 conventional CPR OR conventional cardiopulmonary resuscitation #13 #11 OR #12

#14 out-of-hospital cardiac arrest OR out of hospital cardiac arrest #15 cardiac arrest AND out-of-hospital,

#16 arrest AND out-of-hospital,

#17 cardiac arrest AND out of hospital, #18 arrest AND out of hospital,

#19 #14 OR #15 OR #16 OR #17 OR #18

#20 #6 OR #10 OR #13

#21 #19 AND #20

#22 #21 limit to human

References

1. Lloyd-Jones D, Adams R, Carnethon M, et al. Heart disease and stroke statistics- 2009 update: a report from the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Circulation 2009;119:480-6.
2. Berg RA, Hemphill R, Abella BS, et al. Part 5: adult basic life support: 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation 2010;122:S685-705.
3. Sayre MR, Koster RW, Botha M, et al. Part 5: adult basic life support: 2010 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. Circulation 2010;122:S298-324.
4. Stiell I, Nichol G, Wells G, et al. health-related quality of life is better for cardiac arrest survivors who received citizen cardiopulmonary resuscitation. Circulation 2003;108:1939-44.
5. Sasson C, Rogers MA, Dahl J, et al. Predictors of survival from out-of-hospital cardiac arrest: a systematic review and meta-analysis. Circ Cardiovasc Qual Outcomes 2010;3:63-81.
6. Hallstrom A, Cobb L, Johnson E, et al. Cardiopulmonary resuscitation by chest compression alone or with mouth-to-mouth ventilation. N Engl J Med 2000;342:1546-53.
7. Svensson L, Bohm K, Castren M, et al. Compression-only CPR or standard CPR in out-of-hospital cardiac arrest. N Engl J Med 2010;363:434-42.
8. Rea TD, Fahrenbruch C, Culley L, et al. CPR with chest compression alone or with rescue breathing. N Engl J Med 2010;363:423-33.
9. Cabrini L, Biondi-Zoccai G, Landoni G, et al. Bystander-initiated chest compres- sion-only CPR is better than standard CPR in out-of-hospital cardiac arrest. HSR Proc Intensive Care Cardiovasc Anesth 2010;2:279-85.
10. Hupfl M, Selig HF, Nagele P. Chest-compression-only versus standard cardiopul- monary resuscitation: a meta-analysis. Lancet 2010;376:1552-7.
11. Kitamura T, Iwami T, Kawamura T, et al. Bystander-initiated rescue breathing for out-of-hospital cardiac arrests of noncardiac origin. Circulation 2010;122:293-9.
12. Group JCSRSS. Chest-compression-only bystander cardiopulmonary resuscitation in the 30:2 compression-to-ventilation ratio era. Circ J 2013;77:2742-50.
13. Kitamura Tetsuhisa, Iwami Taku, Kawamura Takashi, et al. Time-dependent effectiveness of chest compression-only and conventional cardiopulmonary resuscitation for out-of-hospital cardiac arrest of cardiac origin. Resuscitation 2011;82:3-9.
14. Stroup DF, Berlin JA, Morton SC, et al. Meta-analysis of observational studies in epidemiology: a proposal for reporting. JAMA 2000;283:2008-12.
15. Ong ME, Ng FS, Anushia P, et al. Comparison of chest compression only and standard cardiopulmonary resuscitation for out-of-hospital cardiac arrest in Singapore. Resuscitation 2008;78:119-26.
16. Van Hoeyweghen RJ, Bossaert LL, Mullie A, et al. Quality and efficiency of bystander CPR. Resuscitation 1993;26:47-52.
17. Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovas- cular Care. Part 6: advanced cardiovascular life support: Section 8: postresuscita- tion care. The American Heart Association in collaboration with the International Liaison Committee on Resuscitation. Circulation 2000;102:I166-I171.
18. group S-Ks. Cardiopulmonary resuscitation by bystanders with chest compression only (SOS-KANTO): an observational study. Lancet 2007;369:920-6.
19. Higgins JP, Thompson SG, Deeks JJ, et al. Measuring inconsistency in meta- analyses. BMJ 2003;327:557-60.
20. Stang A. Critical evaluation of the Newcastle-Ottawa Scale for the assessment of the quality of nonrandomized studies in meta-analyses. Eur J Epidemiol 2010;25:603-5.
21. Waalewijn RA, Tijssen JG, Koster RW. Bystander initiated actions in out-of- hospital cardiopulmonary resuscitation: results from the Amsterdam Resuscita- tion Study (ARRESUST). Resuscitation 2001;50:273-9.
22. Iwami T, Kawamura T, Hiraide A, et al. Effectiveness of bystander-initiated cardiac- only resuscitation for patients with out-of-hospital cardiac arrest. Circulation 2007;116:2900-7.
23. Bohm K, Rosenqvist M, Herlitz J, et al. Survival is similar after standard treatment and chest compression only in out-of-hospital bystander cardiopulmonary resuscitation. Circulation 2007;116:2908-12.
24. Olasveengen TM, Wik L, Steen PA. standard basic life support vs. continuous chest compressions only in out-of-hospital cardiac arrest. Acta Anaesthesiol Scand 2008;52:914-9.
25. Sayre MR, Berg RA, Cave DM, et al. Hands-only (compression-only) cardiopul- monary resuscitation: a call to action for bystander response to adults who experience out-of-hospital sudden cardiac arrest: a science advisory for the public from the American Heart Association Emergency Cardiovascular Care Committee. Circulation 2008;117:2162-7.
26. Bobrow BJ, Spaite DW, Berg RA, et al. Chest compression-only CPR by lay rescuers and survival from out-of-hospital cardiac arrest. JAMA 2010;304:1447-54.