Hallstrom 2000.
| Methods | Randomized controlled trial | |
| Participants | Inclusion criteria: Participants who were recognized to be unconscious and not breathing normally by callers who willing to undertake CPR with the dispatcher's assistance Exclusion criteria: Cases in which there was no cardiac arrest; cases of drug overdose, alcohol intoxication, or carbon monoxide poisoning; cases in which advanced cardiac life support was not carried out; and cases due to trauma. And the caller was not at the scene, or cardiac arrest occurred after the call 520 participants were included |
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| Interventions | Intervention group: the bystander was instructed to perform chest compressions alone Contral group: the bystander was instructed to perform chest compressions plus rescue breathing, with 2 initial rescue breaths followed by 15 chest compressions and subsequent cycles continuing the pattern in a ratio of 2 to 15 |
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| Outcomes | The primary end point was survival to hospital discharge. Secondary end points included admission to the hospital and estimated neurologic status in the survivors | |
| Notes | The study started before the guidelines for CPR changed the recommendation from 2 ventilations alternating with 15 compressions to 30 compressions alternating with 2 ventilations.The instructions in this study of 2 ventilations alternating with 15 compressions were maintained | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | Randomization was assigned by a microcomputer located at the dispatcher's console |
| Allocation concealment (selection bias) | Unclear risk | If the caller was willing to be instructed, the caller was given instructions for performing either continuous chest compression alone or interrupted chest compression plus mouth‐to‐mouth ventilation, as randomly assigned by a microcomputer located at the dispatcher's console |
| Blinding of participants and personnel (performance bias) All outcomes | Low risk | The bystanders were not blinded, but they did not know that they were recruited in this study, so we considered it having minimal effects on the rescue treatment. Performance bias is unlikely to affect the primary outcomes of interest in the review |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | In the study, emergency medical services personnel other than those in the dispatch office were generally unaware that an episode might be part of a trial. The paramedics who completed the field reports typically arrived after the first responding personnel and thus had limited knowledge of the type or quality of bystander CPR that may have been performed. Hospitalization data and functional status after discharge from the hospital were obtained through an existing follow‐up programme whose personnel were unaware of the treatment assignments |
| Incomplete outcome data (attrition bias) All outcomes | Low risk | Data on discharge were not available for two participants who were admitted to the hospital, one in each treatment group |
| Selective reporting (reporting bias) | Low risk | Main outcomes of out‐of‐hospital cardiac arrest were reported in full |
| Other bias | Low risk | We did not identify other sources of bias |