Drowning in Denmark: A Six-year Registry-based Study of Fatal and Non-fatal Drowning

Study Overview
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Brief Summary
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Within a six-year period from 2016-2021, this retrospective cohort study aims to report: 1) the national incidence of non-fatal drowning accidents attended by the Danish Emergency Medical Services (EMS), 2) 48-hours and 30-day mortality, 3) Duration of hospitalization, 4) Neurological outcome at hospital discharge Furthermore, the investigators will follow the recommended guidelines for uniform reporting of data from drowning the Utstein style and investigate aspects associated with better outcome. Finally, the investigators wish to report spatial distribution of non-fatal drowning accidents. This can potentially result in recommendations towards certain educative, preventative, rescue, or treatment strategies to reduce OHCA from drowning.

Detailed Description
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Introduction Preventing drowning accidents is of great interest, as a large proportion of drowning events can be avoided by proper educative and targeted preventative measures. Yet, effective educative, preventative, rescue, and treatment interventions to reduce drowning events require accurate, reliable, and sufficient data to be scientifically analysed. However, the complexity of the disease, various drowning terminology, definitions, and an inappropriate classification of drowning events even in high-income countries possess a great challenge when trying to gather sufficient data. Currently, drowning is a major cause of mortality worldwide, and a leading cause of cardiac arrest in children and adolescents. Even in highly developed countries, the incidence of drowning is highest among children less than 5 years of age and in young adults between 15 and 24 years of age. The duration of submersion plays a key role in determining the outcome from drowning, as submersion exceeding 10 minutes is associated with poor outcome. Furthermore, drowning leading to hypoxic cardiac arrest is a reversible cause that can be treated. Therefore, bystanders, trained rescuers (e.g., trained lifeguards) and EMS personnel play a critical role in the initial attempts at rescue and resuscitation to prioritise oxygenation and ventilation. Yet, research on drowning accidents is limited, and under-reporting contributes significantly to misunderstanding of the process of drowning. This leads to a potential for improvement, which requires first and foremost clarification of the most obvious causes and risk factors associated with drowning following recommended guidelines for uniform reporting of data. Data on non-fatal drowning accidents are not routinely collected in many countries, hence non-fatal drowning statistics are not readily available or are unreliable in many countries. However, analysing non-fatal drowning accidents is equally important to fatal drowning accidents to better understand the process of drowning and to design intervention strategies to decrease the mortality, morbidity, and the total number of drowning accidents worldwide. Thus, within a six-year period from 2016-2021, this retrospective cohort study aims to report: 1) the national incidence of non-fatal drowning accidents attended by the Danish Emergency Medical Services (EMS), 2) 48-hours and 30-day mortality, 3) Duration of hospitalisation, 4) Neurological outcome at hospital discharge. Furthermore, the investigators will follow the recommended guidelines for uniform reporting of data from drowning the Utstein style and investigate aspects associated with better outcome. Finally, the investigators wish to report spatial distribution of non-fatal drowning accidents. Aim The aim of this study is to report baseline characteristics for drowning following the recommended guidelines for uniform reporting of data from drowning the Utstein style and investigate aspects associated with better outcome. The results of this study can be used to establish recommendations towards certain educational, preventative, rescue, or treatment strategies to reduce the number of drowning accidents. Methods Terminology: Drowning is defined by the WHO in 2002 as the process of experiencing respiratory impairment from submersion or immersion in liquid. Submersion is the situation where the victim's entire body, including the airway, goes below the surface of the liquid. Immersion is to be covered in water, and for drowning to occur, usually at least the face and airway are immersed. The internationally accepted clarification statement for non-fatal drowning is: Drowning outcomes are fatal or non-fatal. In non-fatal drowning, the process of respiratory impairment is stopped before death. Implicitly, a case should be categorised as a non-fatal drowning if the person experienced respiratory impairment from submersion/immersion in liquid but did not die. According to the Clarification and Categorization of Non-fatal Drowning if a person was drowning and can be ascertained to have been experiencing either mild, moderate, or severe respiratory impairment immediately after the drowning process ended, the case should be categorised as a non-fatal drowning case regardless of morbidity. However, if the person did not experience respiratory impairment from submersion/immersion in liquid, it should not be categorised as non-fatal drowning (e.g., a person who were swimming and accidentally inhaled some water and as a result voluntarily coughed to clear their airway, or if a rescue intervention occurs to assist an apparently distressed person in the water, but there was no sign of respiratory impairment). If the person dies because of drowning, this is termed a fatal drowning. Any submersion or immersion event without evidence of respiratory impairment is considered a water rescue and not a drowning. Setting: In an on-going study the investigators have created a text search string to be used in advanced text searching in the entire pre-hospital electronic medical records system since 2016 for cases with OHCA following drowning (the protocol is available in English from the corresponding author upon request). This enables the possibility for advanced text searching in the entire nationwide electronic medical reporting system used by the Danish EMS to identify drowning accidents attended by the EMS, based on identification of trigger-words in the electronic medical record. Identification of non-fatal drowning accidents: During an on-going study of drowning-related OHCA's Breindahl N et al. developed a text search-string to identify potential cases of drowning from the Danish Cardiac Arrest Registry using data from the pre-hospital electronic medical records. However, to ensure high sensitivity and specificity of a text search-string to identify non-fatal drowning accidents, revised search-strings, manual verification across EMS regions and further data cleansing are needed. Initially, the investigators will apply the original text search-string on the entire nationwide electronic medical reporting system used by the Danish EMS. The investigators will identify true positives and add relevant trigger-words to the text search-string by manually reading through the medical records until no more true positives are identified, thereby increasing sensitivity. Meanwhile, the investigators will add relevant rule-out-words to minimise the number of false positives, thereby increasing specificity. This iterative process will be performed until a minimal number of new reports appear, and the investigators will have identified the final number of non-fatal drowning accidents. The remaining four regions have all pledged data permission and agreed to initiate the study when funding has been acquired. The result will be a text-string which can be used prospectively to search note-fields within the electronic medical records and identify drowning accidents. The identified text string will be used both for the EMS as well as the HEMS data. The two cohorts will be separated as fatal vs non-fatal if the patient dies because of drowning or as a consequence of his/her injuries.

Official Title
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Drowning in Denmark: A Danish Nationwide Six-year Registry-based Study on Aetiology, Incidence, Survival, and Spatial Distribution of Fatal and Non-fatal Drowning Accidents

Conditions
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Drowning

Intervention / Treatment
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* Other: Drowning accident


Participation Criteria
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Eligibility Criteria
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Inclusion criteria: The patient must have been experiencing respiratory impairment from submersion or immersion in liquid on land/in coastal/lake/river areas AND The patient must have been in contact with the Danish EMS (ambulance or Helicopter Emergency Medical Service/HEMS). Exclusion criteria: Patients with a valid Do-Not-Attempt-Resuscitation (DNAR) code OR Patients with obvious clinical signs of irreversible death (decapitation, decomposition, postmortem lividity, postmortem rigidity).
Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Fatal drowning accident<br>Fatal drowning accident where the patient died because of the drowning process or as a consequence of his/her injuries. | Other: Drowning accident<br>* Drowning is defined by the WHO in 2002 as the process of experiencing respiratory impairment from submersion or immersion in liquid<br>|
| Non-fatal drowning accident<br>Non-fatal drowning accident where the patient was drowning and can be ascertained to have been experiencing either mild, moderate, or severe respiratory impairment immediately after the drowning process ended but did not die. | Other: Drowning accident<br>* Drowning is defined by the WHO in 2002 as the process of experiencing respiratory impairment from submersion or immersion in liquid<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Fatal vs. non-fatal incidence ratios per 100,000 from 2016-2021 | Stratified by the most obvious causes and risk factors following recommended guidelines for uniform reporting of data from drowning including age, sex, precipitating event, geographical localization, and type of activity | Counts of fatal and non-fatal drowning accidents will be obtained between 2016-2021 to calculate the incidence ratios | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Map of fatal and non-fatal drowning accidents in Denmark from 2016-2021 | Showing a map of geographical localization of drowning in Denmark in the study period indicating 30-day mortality and survival | 5-year period from 2016-2021 | 
| Annual survival rates of drowning per 100,000 from 2016-2021 | Stratified by the most obvious causes and risk factors following recommended guidelines for uniform reporting of data from drowning including precipitating event, geographical localization, and type of activity | Annually from 2016-2021 (at the end of the year) | 
| Duration of hospitalisation | Duration of hospitalisation from admission to discharge measured in days | From hospital admission to discharge (up to 30 days) | 
| Duration of ICU stay | Duration of intensive care unit (ICU) stay from admission to discharge measured in days | From ICU admission to discharge (up to 30 days) | 
| Duration of mechanical ventilation | Duration of mechanical ventilation from intubation to extubation measured in hours | From intubation to extubation (up to 30 days) | 
| Neurological outcome at discharge | Neurological outcome was calculated using the Cerebral Performance Categories (CPC) scale | At hospital discharge (up to 30 days) | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Drowning, Non-fatal, Utstein style, Register study, Retrospective