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1 Resuscitation 85 (2013) Contents lists available at ScienceDirect Resuscitation journal homepage: Clinical paper Direction of first bystander call for help is associated with outcome from out-of-hospital cardiac arrest Z. Nehme a,b,, E. Andrew a,b, P. Cameron b, J.E. Bray b, I.T. Meredith c, S. Bernard a,b, K. Smith a,b,d a Ambulance Victoria, Doncaster, Victoria, Australia b Monash University, Prahran, Victoria, Australia c Monash Medical Centre, Clayton, Victoria, Australia d University of Western Australia, Crawley, Western Australia, Australia article info abstract Article history: Received 20 June 2013 Received in revised form 29 July 2013 Accepted 22 August 2013 Keywords: Heart arrest Cardiopulmonary resuscitation Emergency medical services First aid Background: Preventable bystander delays following out-of-hospital cardiac arrest (OHCA) are common, and include bystanders inappropriately directing their calls for help. Methods: We retrospectively extracted Utstein-style data from the Victorian Ambulance Cardiac Arrest Registry (VACAR) for adult OHCA occurring in Victoria, Australia, between July 2002 and June Emergency medical service (EMS) witnessed events were excluded. Cases were assigned into two groups on the basis of the first bystander call for help being directed to EMS. Study outcomes were: likelihood of receiving EMS treatment; survival to hospital, and; survival to hospital discharge. Results: A total of adult OHCA cases attended by EMS were identified, of which first bystander calls for help were not directed to EMS in 2842 (6.4%) cases. Calls to a relative, friend or neighbour accounted for almost 60% of the total emergency call delays. Patient characteristics and survival outcomes were consistently less favourable when calls were directed to others. First bystander call to others was independently associated with older age, male gender, arrest in private location, and arrest in a rural region. The risk-adjusted odds of treatment by EMS (OR 1.33, 95% CI ), survival to hospital (OR 1.64, 95% CI ) and survival to hospital discharge (OR 1.64, 95% CI ) were significantly improved if bystanders called EMS first. Conclusion: The frequency of inappropriate bystander calls following OHCA was low, but associated with a reduced likelihood of treatment by EMS and poorer survival outcomes. Crown Copyright 2013 Published by Elsevier Ireland Ltd. All rights reserved. 1. Introduction Out-of-hospital cardiac arrest (OHCA) is a leading cause of death in Western countries, and is estimated to affect people each year in the United States alone. 1 The chain of survival is designed to improve favourable outcomes from OHCA through the promotion of time-dependent actions, including the initiation of effective chest compressions, early defibrillation and access to advanced life support. 2 While a number of reports have described the importance of these three actions on survival from OHCA, 3 6 few have focused on the A Spanish translated version of the summary of this article appears as Appendix in the final online version at Corresponding author at: Department of Research and Evaluation, Ambulance Victoria, 375 Manningham Road, PO Box 2000, Doncaster, Victoria 3108, Australia. Tel.: ; fax: address: Ziad.Nehme@ambulance.vic.gov.au (Z. Nehme). significance of the first link in the chain defined as early access, or early bystander recognition and appropriate action following OHCA. The frequency of preventable bystander delays following OHCA is high, with the greatest cause of delay being attributed to bystanders inappropriately directing their calls for help. 7 Delays occurring prior to emergency medical service (EMS) activation have an important impact on the sequence of the chain of survival, potentially delaying the receipt of early and effective bystander cardiopulmonary resuscitation (CPR) and prolonging the time to definitive treatment by EMS. Given that previous reports have demonstrated that inappropriate bystander action may be adversely associated with outcome from OHCA, 7 9 there is a need to identify the impact of bystander call direction on survival from OHCA. Since 1999, the Victorian Ambulance Cardiac Arrest Registry (VACAR) has captured population-based data from OHCA events in Victoria, Australia, including the capture of bystander call direction from EMS treatment and dispatch records. Given the paucity of /$ see front matter. Crown Copyright 2013 Published by Elsevier Ireland Ltd. All rights reserved.

2 Z. Nehme et al. / Resuscitation 85 (2013) Data sources Fig. 1. Adult patient selection between July 2002 and June reports describing this preventable cause of delay to EMS access, we sought to describe the direction and impact of the first bystander call for help on survival from OHCA. 2. Methods 2.1. Study design This investigation was a retrospective observational study of population-based data extracted from the VACAR. All adult patients aged greater than 15 years (or missing age), who suffered an OHCA between 1st July 2002 and 30th June 2012 were included in the analysis (see Fig. 1). EMS witnessed OHCA were excluded Setting The state of Victoria, Australia, has a population of approximately 5.6 million people, of which four million people reside in the city of Melbourne. The state s EMS comprises approximately 3000 paramedics who respond in a two-tier system. Advanced life support (ALS) and mobile intensive care ambulance (MICA) paramedics are dispatched concurrently to suspected cardiac arrest events in the community. A first responder programme for early defibrillation by fire-fighters and volunteer community emergency response teams operates in areas of Melbourne, and smaller rural communities across the state. 10 For victims of cardiac arrest, paramedic clinical practice guidelines follow the recommendations of the Australian Resuscitation Council ( 11 Paramedics operating in Victoria are authorised to withhold or cease resuscitation in the field in accordance with clinical practice guidelines. Australia operates a single national telephone number for community access to emergency services (i.e. 000 ). The Emergency Services Telecommunications Authority manages the triage of emergency calls for all emergency services in the state of Victoria. At the callers request, calls can be directed to Ambulance and undergo medical triage using a structured electronic call-taking algorithm (Medical Priority Dispatch System ). Calls identified as suspected cardiac arrest events receive further calltaker instruction recommending 400 chest compressions before mouth-to-mouth resuscitation. 12 The VACAR is a population-based registry containing Utsteinstyle data for all EMS attended OHCA events in the state of Victoria, Australia. 13 In-field clinical and operational data are recorded electronically by paramedics using a computer tablet and synchronised daily to a central clinical database. The VACAR uses a highly sensitive search algorithm to identify cases whose clinical observations, clinical interventions, or assessments are consistent with an attendance at a cardiac arrest. Review of computer-aided dispatch records and paper-based patient care records submitted to the billing department supplements the identification of potential cases. Paramedics are also required to self-report cardiac arrest cases to team managers, with hardcopies of treatment records and monitored rhythms sent to VACAR for review. All potential cases are reviewed for eligibility by registry personnel and entered into the database according to the Utstein requirements. 13 Hospital discharge status follow-up data is obtained from hospital medical records for approximately 99% of all transported cases. Hospital outcome data is cross-validated against death records from the Victorian Registry of Births Deaths and Marriages. Data collection is standardised, and subject to ongoing quality control procedures. Data extracted from VACAR contains patient demographics, treatment and operational data, and the Utstein-style elements. 13 Arrests are presumed to be of cardiac aetiology unless the aetiology is identified on the patient care record (e.g. trauma, submersion, drug overdose, exsanguination etc.). The time elements EMS response time and First shock time are recorded from the start time of emergency call, and end on arrival of the first EMS team to the scene or the first delivered defibrillation respectively. The term prolonged downtime is an estimated variable denoting that the period between suspected cardiac arrest and EMS arrival exceeds 15 min. Bystander CPR was defined as any attempt at chest compressions, with or without ventilations, as observed on arrival of EMS personnel. The direction of first bystander call for help is defined as the individual or organisation that received the first call for help from a bystander on scene (Table 1). As this is difficult to determine without direct interview of the bystander, VACAR appraises two sources of data to identify this information. Firstly, case histories from patient care records are screened to identify instances of call delay obtained from the paramedic s interview with bystanders on scene. Secondly, a log of dispatch records is screened to identify suspected cardiac arrest events referred by a third party (e.g. doctor, friend, neighbour etc.) or another emergency/government service (e.g. Police, or health advice services). If no reference to call direction is identified on review of the available information, VACAR assumes that the bystander called EMS first Statistical analyses The sample population was assigned into the groups Called EMS or Called Other depending on the direction of the first bystander call (Table 1). Patient characteristics and outcomes within EMS-attended and EMS-treated samples were compared across the bystander call groups using Pearson s chi-square test or t-test where appropriate. We excluded 346 (0.8%) cases with missing call direction from all comparisons. We stratified the frequency of EMS attempted resuscitations (i.e. EMS treatment) across call groups by arrest locations and arrest aetiologies, and compared them using Pearson s chi-square test. All comparisons were presented as odds ratios and 95% confidence intervals. A multivariate model was used to identify patient characteristics associated with a first bystander call to EMS.

3 44 Z. Nehme et al. / Resuscitation 85 (2013) Table 1 Description and frequency of first bystander call for help used in the study analysis. Groups Sub-groups Frequency of calls Description EMS attended, No. EMS treated, No. (% of EMS attended) Unknown call direction (23.1) Bystander call direction was missing Called EMS (40.4) Includes cases where the bystander called ambulance in the first instance following OHCA. Cases were assumed to be directed to ambulance unless otherwise stated Called other Relative or friend (37.1) Includes calls to immediate family members, relatives or friends Doctor or health professional (31.6) Includes calls to doctors, and other health professionals, including pharmacists, nurses and physiotherapists. Calls to health advice services were also included Neighbour (50.5) Includes calls to any neighbour Police (15.5) Includes incidents where Police members (or Police dispatch) refer a call to ambulance following a call from a bystander on scene Other person (12.5) Another person or organisation which does not fit the above sub-categories All sub-groups (33.1) Includes all Called other sub-groups The impact of call direction on the likelihood of treatment by EMS and survival outcome was evaluated using a logistic regression model adjusted for known predictors of survival, including: age, gender, arrest in a public location, initial shockable rhythm, bystander witnessed, bystander CPR, EMS response time, arrest aetiology, and metropolitan region. 4,14 Effect sizes were presented as adjusted odds ratios and 95% confidence intervals. The threshold for statistical significance was p < All statistical analyses were undertaken using PASW Statistics 18 (SPSS Inc., Chicago, IL, USA) Ethics approval The Victorian Department of Health Human Research Ethics Committee has classified VACAR and this study as quality assurance projects. The use of patient follow-up data has been approved by hospital ethics/research committees participating in the VACAR. Ethical approval was also granted by the Monash University Human Research Ethics Committee. 3. Results The patient selection algorithm is shown in Fig. 1. A total of adult OHCA cases attended by EMS were identified during the study period, with (39.8%) receiving an attempted resuscitation (EMS-treated population, Fig. 1) Direction of first bystander call Of the adult OHCA cases included in the analysis, we excluded 346 (0.8%) cases with missing call direction. First bystander call for help was directed to others in 2842 (6.4%) cases (Table 1). Calls to a relative/friend or neighbour accounted for almost 60% of the total calls to others, with the remaining calls being directed to Police (16.5%), a doctor or health professional (15.6%), or other person (8.7%). The proportion of EMS-treated cases in the Called Other group was 33.1%, compared with 40.4% for cases directed to EMS first (OR 1.37, 95% CI , p < ) Patient characteristics Patient and arrest characteristics and Utstein-style descriptors are presented in Table 2 for the EMS-attended and EMStreated populations. Patient characteristics were consistently less favourable in the Called Other group across both populations. The Called Other group were older in age, had longer EMS response times, and observed fewer bystander witnessed arrests and arrests in a public location. The Called EMS group had fewer cases with prolonged downtime (59.1% vs. 74.1%) and were more likely to observe shockable rhythms on arrival of EMS (13.7% vs. 8.1%). Arrests in rural areas were more likely to see the first bystander call for help being directed to others (29.0% vs. 33.6%). Patient characteristics that were independently associated with a call to EMS were: younger age, female gender, public location, and an arrest in the metropolitan region (Table 3) Outcomes The frequency of return of spontaneous circulation (ROSC), survival to hospital and survival to hospital discharge was less favourable for cases whose bystander calls were directed to others (Table 2). The proportion of EMS-treated cases whose resuscitation efforts were ceased at scene was significantly higher in the Called Other group (62.2% vs. 78.8%). When compared to the Called EMS group, the unadjusted odds of survival to hospital discharge in the Called Other group was 0.36 (95% CI ). The unadjusted relationship between call direction and likelihood of receiving an attempted resuscitation by EMS was stratified according to arrest location (Table 4) and arrest aetiology (Table 5). The Called EMS group were significantly more likely to receive an attempt at resuscitation across all arrest locations. When stratified according to arrest aetiology, the direction of bystander call did not appear to influence treatment decisions in traumatic arrests, although was associated with fewer resuscitation attempts in the cardiac and other aetiology groups (i.e. respiratory, drug overdose, exsanguination etc.). Multivariate modelling identified calls to EMS as an independent predictor of receiving treatment by EMS (OR 1.33, 95% CI , Table 3). The direction of the first bystander call for help was also independently associated with survival outcome from OHCA. When compared with the Called Other group, the risk-adjusted odds of survival to hospital (OR 1.64, 95% CI ) and survival to hospital discharge (OR 1.64, 95% CI ) were significantly in favour of bystanders calling EMS first (Table 3). 4. Discussion Bystander recognition of cardiac arrest and immediate activation of EMS is arguably the most important element of the chain of survival, and a key public health initiative. 2 The importance of early recognition and call to EMS has been demonstrated in

4 Table 2 Patient and arrest characteristics for EMS-attended and EMS-treated populations grouped by the direction of first bystander call for help. Overall, n = EMS attended population OR (95% CI) EMS treated population OR (95% CI) Called EMS n = Called other n = 2842 Called EMS n = Called other n = 942 Age in years, mean (95% CI) 65.3 ( ) 65.1 ( ) 68.2 ( ) 3.06 ( ) *, 64.5 ( ) 68.8 ( ) 4.30 ( ) *, Unknown, No. (%) 1456 (3.3) 1365 (3.3) 51 (1.8) 73 (0.4) 1 (0.1) Male gender, No (%) (66.0) (65.8) 1934 (68.1) 1.10 ( ) (69.3) 678 (72.0) 1.09 ( ) Unknown, No. (%) 229 (0.5) 212 (0.5) 7 (0.2) 5 (0.0) 0 (0.0) EMS response time (mins), 10.1 ( ) 10.1 ( ) 11.0 ( ) 0.92 ( ) *, 9.3 ( ) 9.8 ( ) 0.49 ( ) *, mean (95% CI) Unknown, No (%) 532 (1.2) 487 (1.2) 31 (1.1) 105 (0.6) 4 (0.4) Prolonged downtime, No. (%) (60.1) (59.1) 2107 (74.1) 1.98 ( ) 3969 (23.8) 427 (45.3) 2.66 ( ) Presumed cardiac aetiology, (72.2) (72.0) 2158 (75.9) 1.23 ( ) (79.4) 791 (84.0) 1.36 ( ) No. (%) Location of arrest, No (%) House (74.3) (73.4) 2512 (88.4) 2.76 ( ) (66.8) 843 (89.5) 4.24 ( ) Aged care facility 3154 (7.1) 3058 (7.4) 76 (2.7) 0.34 ( ) 1246 (7.5) 19 (2.0) 0.26 ( ) Public place 7868 (17.7) 7554 (18.3) 221 (7.8) 0.38 ( ) 4159 (24.9) 68 (7.2) 0.23 ( ) Other 409 (0.9) 371 (0.9) 33 (1.2) 1.30 ( ) 147 (0.9) 12 (1.3) 1.45 ( ) First monitored rhythm, No. (%) Shockable 600 (13.3) 5679 (13.7) 230 (8.1) 0.55 ( ) 5640 (33.7) 228 (24.2) 0.62 ( ) Asystole (75.7) (75.1) 2395 (84.3) 1.75 ( ) 6925 (41.5) 529 (56.2) 1.80 ( ) Pulseless electrical activity 4476 (10.1) 4265 (10.3) 193 (6.8) 0.63 ( ) 3877 (23.2) 171 (18.2) 0.73 ( ) Not shockable 197 (0.4) 176 (0.4) 16 (0.6) 1.32 ( ) 127 (0.8) 10 (1.1) 1.40 ( ) Unknown 202 (0.5) 183 (0.5) 8 (0.3) 136 (0.8) 4 (0.4) First shock time (mins): all 16.8 ( ) 16.7 ( ) 18.6 ( ) 1.89 ( ) * 16.7 ( ) 18.6 ( ) 1.89 ( ) * defibrillated patients, mean (95% CI) First shock time (mins): 12.1 ( ) 12.1 ( ) 12.9 ( ) 0.75 ( ) * 12.1 ( ) 12.9 ( ) 0.75 ( ) * shockable rhythm on arrival, mean (95% CI) Bystander witnessed, No. (%) (32.0) (32.2) 844 (29.7) 0.89 ( ) 9867 (59.1) 498 (52.9) 0.77 ( ) Unknown 468 (1.1) 382 (0.9) 26 (0.9) 124 (0.7) 3 (0.3) Bystander CPR attempted, (24.2) (24.4) 654 (23.0) 0.93 ( ) 8035 (48.1) 471 (50.0) 1.08 ( ) No. (%) Rural region, No. (%) (29.4) (29.0) 955 (33.6) 1.24 ( ) 3930 (23.5) 273 (29.0) 1.33 ( ) Scene outcomes, No. (%) Efforts ceased at scene (85.3) (84.7) 2642 (93.0) 2.38 ( ) (62.2) 742 (78.8) 2.25 ( ) Transport with ROSC 5136 (11.5) 4952 (12.0) 166 (5.8) 0.46 ( ) 4952 (29.6) 166 (17.6) 0.51 ( ) Transport with CPR 1400 (3.1) 1352 (3.3) 34 (1.2) 0.36 ( ) 1352 (8.1) 34 (3.6) 0.42 ( ) ongoing Unknown 13 (0.0) 13 (0.0) 0 (0.0) 11 (0.1) 0 (0.0) ROSC at any time, No. (%) 6098 (13.7) 5867 (14.2) 213 (7.5) 0.49 ( ) 5867 (35.1) 213 (22.6) 0.54 ( ) Survival to hospital, No. (%) 5157 (11.6) 4974 (12.0) 166 (5.8) 0.45 ( ) 4974 (29.8) 166 (17.6) 0.50 ( ) Unknown 121 (0.3) 117 (0.3) 2 (0.1) 117 (0.7) 2 (0.2) Survival to hospital 1556 (3.5) 1519 (3.7) 33 (1.2) 0.31 ( ) 1519 (9.1) 33 (3.5) 0.36 ( ) discharge, No. (%) Unknown 302 (0.7) 297 (0.7) 4 (0.1) 291 (1.7) 2 (0.2) Abbreviations: OR, odds ratio; CI, confidence interval; CPR, cardiopulmonary resuscitation; ROSC, return of spontaneous circulation. Proportions may not add to 100% due to rounding. * Mean difference (95% CI). Statistically significant (p < 0.05). Survival to hospital denotes a pulse present on arrival to hospital. Z. Nehme et al. / Resuscitation 85 (2013)

5 46 Z. Nehme et al. / Resuscitation 85 (2013) Table 3 Multivariate analysis examining factors predicting first call to EMS (n = ), treatment being commenced by EMS (n = ), survival to hospital (n = ) and survival to hospital discharge (n = ). Covariates First call to EMS Treatment by EMS Survival to hospital Discharged alive OR (95% CI) p-value OR (95% CI) p-value OR (95% CI) p-value OR (95% CI) p-value Age (years) 0.99 ( ) < ( ) < ( ) ( ) < Female gender 1.22 ( ) < ( ) NS 1.38 ( ) < ( ) EMS response time Not included 0.97 ( ) < ( ) < ( ) < Public location 2.34 ( ) < ( ) NS 1.14 ( ) ( ) < Initial shockable rhythm Not included ( ) < ( ) < ( ) < Cardiac aetiology 1.03 ( ) NS 1.60 ( ) < ( ) < ( ) Bystander witnessed 1.00 ( ) NS 6.96 ( ) < ( ) < ( ) < Bystander CPR attempted 0.95 ( ) NS 6.63 ( ) < ( ) < ( ) < Metropolitan region 1.29 ( ) < ( ) < ( ) < ( ) < First call to EMS Not included 1.33 ( ) < ( ) < ( ) Abbreviations: EMS, emergency medical service; CPR, cardiopulmonary resuscitation; OR, odds ratio; CI, confidence interval. conditions such as stroke 15 and acute myocardial infarction, 16 although there are relatively few authors who have evaluated the impact of emergency call delays on outcome from OHCA. 17 Recent work by Swor et al. established that delays prior to emergency call may be present in as many as half of all OHCA, and is associated with poorer survival. 8 Similarly, preventable bystander delays prior to the emergency call have been adversely associated with outcome by numerous other authors. 7 9 In the present study, we identified that 6.4% of all adult OHCA were associated with an emergency call delay, where bystanders failed to refer their distress calls to EMS in the first instance. Calls to family, relatives or neighbours were responsible for almost 60% of all emergency call delays observed in this study. Takei et al. reported that calls to the home doctor, family, relatives, friends and neighbours was present in 10.8% of OHCA cases in Japan, and was the leading cause of preventable bystander delays following collapse. 7 Similarly, earlier reports from London and areas of rural Iowa suggested that patients may favour contact with a family member or physician before activation of EMS. 18,19 Preventable bystander action in the home is of particular concern, 7,9 with 88.4% of all inappropriate bystander calls in our study also occurring in the home. Failing to recognise the urgency of these events was also a concern, with many choosing to direct their calls to the family doctor or health advisory service instead. A relatively low frequency of inappropriate calls for help in public places was also observed, and may partly explain its survival advantage in multivariate models. 14 These findings support previous suggestions that immediate family members are at increased risk of inappropriately responding to a cardiac arrest event. 7,8 A recent report by Akahane and colleagues identified that witnessed OHCA events involving family bystanders resulted in significantly worse outcomes than when compared to non-family bystanders. 20 Importantly, family bystanders were associated with significantly longer collapse-to-call delays, fewer attempts at bystander CPR, and longer delays to the administration of bystander CPR. There is relatively little understanding about why bystanders fail to respond to these events with a heightened level of urgency. Interviews with bystanders have provided valuable insight into the emotional milieu associated with OHCA events, with many reporting that panic, fear of poor performance and lack of training were common deterrents to performing bystander CPR. 21 However, it is also clear that delayed or failed recognition of cardiac arrest may also contribute to a lack of bystander action, with as many as 80% of bystanders without first aid training failing to recognise the signs of cardiac arrest. 22 Breckwoldt et al. identified that favourable perceptions of cardiac arrest included descriptions about changes in the victim s skin colour and breathing pattern. This knowledge is valuable as under-prioritisation of emergency calls may have partly contributed to the poorer EMS response times observed in the Called Other group, with similar findings being observed by other authors. 7 Improved recognition of OHCA by bystanders with first aid training has also been recognised, 22 although this did not necessarily lead to higher rates of bystander CPR in groups with a lower incidence of delays. 8,17 If bystander first aid training did influence appropriate call direction in our study, this effect was not coupled with an increased participation in bystander CPR. However, it is plausible that bystanders who directed calls to EMS may have been more likely to commence CPR earlier and preform it more effectively than those who directed their calls to others. Mass media campaigns may be an important mechanism to improving appropriate bystander action following OHCA. While media campaigns have largely improved access to EMS for both myocardial infarction and stroke, there are relatively few reports evaluating their effectiveness in OHCA. Work in this area is methodologically and ethically difficult due to consent issues, incomplete bystander follow-up and resultant selection bias. To some degree, mass media campaigns which target a chest pain population may have an in-direct effect on bystander action following OHCA, although we acknowledge that no previous report has demonstrated a survival benefit with these interventions in a myocardial infarction population. 26 Instead, a collective approach urging the importance of early access in both mass media interventions and bystander first-aid training programmes may be of greater value. 9 Importantly, this study suggests that early access to EMS is fundamental to increasing the opportunity for viable treatment and favourable prognosis following OHCA. To our knowledge this is the first report that has independently associated bystander call direction with survival outcome from OHCA. Furthermore, appropriate bystander calls for help were independently associated with an increased likelihood of treatment by EMS, across all arrest locations and in all but traumatic arrest aetiologies. Our data supports the need to improve the actions taken during the first link in the chain of survival. 5. Limitations This study offers a number of potential limitations. Firstly, its retrospective nature carries widely accepted limitations. Secondly, while we observed a lower rate of inappropriate bystander calls in comparison to previous work, we acknowledge that information taken from EMS records may under-report the true frequency of these delays. Social demographic factors, level of education, and cultural elements may also partly explain the variation in inappropriate bystander action observed across previously published studies. A number of public awareness campaigns, both for myocardial infarction and stroke, have operated in the state of Victoria since 2004 and may have provided an important source of public

6 Table 4 Unadjusted relationship between direction of first bystander call for help and likelihood of treatment by EMS, stratified by arrest location. House OR (95% CI) Aged care facility OR (95% CI) Public place OR (95% CI) Call EMS, n =30328 Called other, n = 2512 n = 3058 Called other, n =76 n = 7554 Called other n = 221 Not treated, No. (%) (63.2) Treated, No. (%) (36.8) 1669 (66.4) Abbreviations: EMS, emergency medical service; OR, odds ratio; CI, confidence interval. Statistically significant result (p < 0.05) ( ) 1812 (59.3) 57 (75.0) 2.06 ( ) 3395 (44.9) 153 (69.2) 843 (33.6) 1246 (40.7) 19 (25.0) 4159 (55.1) 68 (30.8) 2.76 ( ) Table 5 Unadjusted relationship between direction of first bystander call for help and likelihood of treatment by EMS, stratified by arrest aetiology. Cardiac aetiology OR (95% CI) Traumatic Aetiology OR (95% CI) Other Aetiology OR (95% CI) n =29752 Not treated, No. (%) (55.4) Treated, No. (%) (44.6) Called other n = (63.3) Abbreviations: EMS, emergency medical service; OR, odds ratio; CI, confidence interval. Statistically significant result (p < 0.05). n = 3117 Called other n = ( ) 2491 (79.9) 94 (84.7) 1.39 ( ) n = 8442 Called other, n = (66.6) 439 (76.6) 791 (36.7) 626 (20.1) 17 (15.3) 2823 (33.4) 134 (23.4) 1.65 ( ) Z. Nehme et al. / Resuscitation 85 (2013)

7 48 Z. Nehme et al. / Resuscitation 85 (2013) education for the included population. 24 Finally, we acknowledge that an interaction between call delay and outcome may naturally exist in our population. Older, and less informed individuals are both at increased risk of delaying calls to EMS and poorer outcomes following OHCA. In addition, while our survival models were limited to patient s receiving EMS-treatment, we cannot exclude that an imbalance of do-not-resuscitate (DNR) orders between each group contributed to the observed outcomes. 6. Conclusion The frequency of inappropriate bystander calls for help following OHCA is low in a large Australian community, but associated with a reduced likelihood of treatment by EMS and survival from OHCA. Future studies should focus on identifying communities at risk of such actions and improve the dissemination of educational programmes that aim to reduce preventable bystander delays following OHCA. Conflicts of interest None declared. 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