The study aims to investigate bystanders' emotional stress state in out-of-hospital cardiac arrest (OHCA) emergency calls and the association with the quality of dispatcher-assisted cardiopulmonary resuscitation (DA-CPR).

Delayed CPR is believed to be an important factor in the outcome of out-of-hospital cardiac arrest (OHCA). Bystanders' emotional stress state might affect recognition of cardiac arrest and the resuscitation attempt. The study aims to investigate the association between a bystander's emotional stress state at the beginning of the emergency call in out-of-hospital cardiac arrest (OHCA) and dispatcher-assisted cardiopulmonary resuscitation (DA-CPR).

Method

The study is a retrospective and observational study of OHCA emergency calls from the capital region of Denmark from 01.09.2018 - 01.11.2019. The audio recordings of the emergency calls will be obtained from the emergency medical service database. A code catalogue with standardised default descriptions to each variable will be used. The study will only include the first person whom the medical dispatcher talk to. The rating of the calls will be performed by five observers outside of the research group, who have no conflict of interest.

The primary outcome of the present study will be to investigate an association between a bystander's emotional stress state in the beginning of the emergency call of OHCA and the time until first chest compression. Secondarily, the study investigated the association between the bystander's emotional stress and:

Outcome variables:

1. Time to recognition of OHCA, time to initiate CPR, and time to first compression.

2. Assessment of OHCA by the medical dispatcher (Does the dispatcher address patient breathing status and consciousness) (Yes/No)

3. The quality of DA-CPR instructions:

   1. Was the medical dispatcher motivating and encouraging when giving instructions (Yes/No)
   2. Was the medical dispatcher assertive or passive when giving instructions (Yes/No)
   3. Did the medical dispatcher instruct on depth and speed of compressions (Yes/No) Information about caller such as gender and relationship to the patient will also be included in the analyse.

Descriptive analysis of baseline characteristics of emergency calls and dispatchers will be performed by frequency distributions (N %) stratified by emotional stress.

Investigators will use logistic regression on categorical variables to analyse differences in the quality of DA-CPR based on the emotional stress state.

Wilcoxon rank-sum test will be used on non-normally distributed continuous variables to analyse differences in time until first chest compression. Two-way ANOVA will be used to analyse the mean of quantitative variables according to the levels of categorical variables. Furthermore, failure analysis was used to analyse and visualise differences in time until chest compressions based on the emotional stress state.

Kappa statistics were used to assess inter-rater variability and agreement between the reviewers. A Kappa score of overall agreement of 0.72% was found, which provides a substantial agreement between the raters.

Inclusion Criteria:

• All emergency call recordings involving OHCA in the capital region of Denmark in the time period 01.09.2018 - 01.11.2019

Exclusion Criteria:

• Emergency medical services (EMS)-witnessed OHCA
• Missing emergency call recording
• Caller not physically by patient's site

Bystander who call the emergency number in case of OHCA