The chances of surviving an out-of-hospital cardiopulmonary arrest (CPA) can be increased by the execution of 1 tasks by nonprofessional bystanders: immediate activation of the emergency services, good quality cardiopulmonary resuscitation (CPR), and, when possible, the use of a public-access defribrillator. Execution by bystanders of these first links in the survival chain, without waiting for the ambulance to arrive, can maximize the chances of a successful outcome of subsequent advanced life-support interventions.

The goal of this study was to determine the differences in survival and other epidemiological characteristics between CPA patients who received CPR before ambulance arrival and those who did not.

We report the results of an observational study conducted in the Basque Country. The study population included all CPA patients with an indication for CPR who were attended by the emergency ambulance services between June 2016 and May 2018 (digitized data are not available after this date). The study was approved by the Basque Research Ethics Committee. Informed patient consent was not required because the data were extracted from an anonymized database. This centralized out-of-hospital CPA database is compiled by the emergency services coordination unit of the Basque Health Service (Emergentziak-Osakidetza) from standardized documents provided by the public medical emergency system (Sistema de Emergencias Médicas; SEM).

Information was collected on patient sex and age; the place, date, and time of the CPA; the presence of witnesses; whether a nonprofessional bystander performed CPR; and if so whether CPR was initiated with or without telephone support. The study examined in-ambulance electrocardiography data and patient outcome, defined in terms of patient death, immediate survival, and survival to hospital discharge. Outcomes were related to neurological status, assessed according to the Glasgow-Pittsburgh Cerebral Performance Categories (CPC), and to the time elapsed between activation of the SEM and ambulance arrival.

Patient characteristics are presented as absolute numbers and percentages for qualitative variables and as the median [interquartile range] for quantitative variables. Median values were compared by the Kruskal-Wallis test, and associations between qualitative variables were assessed by the chi-square test; differences were considered significant at a 2-sided P value<.05.

During the study period, 1603 out-of-hospital CPA patient events requiring CPR were recorded. Of the patients, 923 (57.6%) did not receive CPR before ambulance arrival. Of the remaining patients, 407 (25.4%) were given CPR by a bystander who did not require telephone support, and 273 (17%) received bystander-initiated CPR with telephone support from the SEM.

Bystander CPR was more frequent among patients younger than 65 years (52.7% vs 35.5%; P <.001) (table 1). Patients receiving bystander CPR had a higher prevalence of defibrillation rhythms (33.7% vs 19.1%; P<.001). Public-access semiautomatic external defibrillators (SAED) were more frequently used by bystanders who did not require telephone support than by those who did (6.8% vs 2.4%; P<.001).

Telephone support for CPR was more frequent when the CPA was witnessed (25.6%; P<.002) or when the event occurred in the patient's home (71.1%; P<.001). In these situations, there was a longer interval between SEM activation and ambulance arrival.

Bystander CPR initiated without the need for telephone support was associated with better immediate patient survival (35.1%; P<.001) and a better clinical condition at discharge (CPC 1-2 in 13% of patients in this category; P<.001). There was no difference in survival between patients who received unguided out-of-hospital CPR and those not receiving CPR before ambulance arrival (24.2% vs 26.4% for immediate survival; P<.45, 7.8% vs 6.2% for survival to discharge; P<.39).

These results demonstrate that the simple act of starting CPR before ambulance arrival does not ensure survival after CPA. Survival after bystander CPR was significantly improved if there was no need for telephone support (probably because the intervening bystander was already familiar with the procedure); however, CPR performed with telephone support did not have the same effect.

To our knowledge, this is the first study published in Spain to stratify survival according to the type of bystander CPR (with or without telephone support). The results contrast with those of another recent study conducted in a different national setting,1 and indicate that the quality of resuscitation maneuvers performed by bystanders receiving telephone support may not be sufficient to generate cerebral circulation. The insufficient quality of CPR performed by bystanders with no life-support training has been reported previously,2 and there is also documented evidence of significant room for improvement in the telephone instructions provided by medical emergency systems.3 A further point of interest is the low rate of SAED use in bystander CPR, despite current legislation authorizing SAED use by members of the public and the mandatory installation of SAED devices at strategic locations4; in the Basque Country, there are currently 104 public-access SAED devices per 100 000 inhabitants.

With the aim of improving survival after CPA, Spanish medical authorities have prioritized the installation of public-access defibrillators and the adoption of recommended practice for the telephone support of bystander CPR by emergency call centers.5 Further efforts are needed, however, to increase skills in CPR technique among members of the general public.