Article Text
PDF
Abstract
Objectives This study aimed to determine whether the association between conventional bystander cardiopulmonary resuscitation (BCPR) and better outcomes in drowning-associated out-of-hospital cardiac arrest (OHCA) differs between young and older people or between non-medical and medical drowning in Japan.
Design Observational study.
Setting This study used data from the Japanese Fire and Disaster Management Agency databases.
Participant Of the 504 561 OHCA cases recorded in the nationwide database between 2016 and 2019, 16 376 (3.2%) were presumably caused by drowning.
Main outcome measure The main outcomes were a 1-month neurological prognosis defined as cerebral performance category 1 or 2 and 1-month survival as measures.
Result The incidence of drowning as a presumed cause of OHCA was high in the winter and the middle-aged and older generations in Japan. However, OHCA caused by drowning in the younger generation frequently occurs in the summer. Furthermore, younger patients had higher incidences of bystander-witnessed cardiac arrest (22.0%), BCPR provision (59.3%) and arrest in outdoor settings (54.0%) than middle-aged and older generations (5.9%, 46.1% and 18.7% respectively). If the patient was younger or the arrest was accidental, the conventional BCPR group had better neurological outcomes than the compression-only BCPR group (95% CI of adjusted OR, 1.22 to 12.2 and 1.80 to 5.57, respectively). However, in the case of middle-aged and older generations and medical categories, there was no significant difference in outcomes between the two types of BCPR. This conventional group’s advantage was maintained even after matching.
Conclusion Conventional bystander CPR yielded a higher neurologically favourable survival rate than compression-only BCPR for OHCA caused by drowning if the patient was younger or the arrest was non-medical. Conventional CPR education for citizens who have the chance to witness drownings should be maintained.
- out-of-hospital cardiac arrest
- accident & emergency medicine
- public health
Data availability statement
Data are available in a public, open access repository. The data analysed in this study were subject to restrictions imposed by the Japanese Fire and Disaster Management Agency. Requests to access these datasets should be directed to the Fire and Disaster Management Agency, 1-2 Kasumigaseki 2-chome, Chiyoda-ku. Tokyo 100-8926, Japan (phone: +81-3-5253-5111; https://www.fdma.go.jp/en/post1.html).
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
Statistics from Altmetric.com
STRENGTHS AND LIMITATIONS OF THIS STUDY
This study specifically examined out-of-hospital cardiac arrest by drowning using a comprehensive database created by combining two databases from the Fire and Disaster Management Agency of Japan.
The difference in the 1 month neurological prognosis between compression-only cardiopulmonary resuscitation (CPR) and conventional CPR was studied while considering the cause of drowning and the age of the drowning patient.
Analyses might have been limited because of insufficient information from bystanders before emergency medical services were contacted.
Introduction
Globally, a high number of drowning-related deaths occur each year. In 2019, an estimated 236 000 people drowned, making it a significant public health problem worldwide.1 To improve the outcomes of out-of-hospital cardiac arrests (OHCAs) caused by drowning, the epidemiological features of OHCAs and the modifiable factors related to their outcomes should be clearly understood.
The majority of drowning victims worldwide are children during the summer. However, in Japan, most drowning victims are older adults during the winter. This is because most houses in Japan have bathtubs, and the Japanese style of bathing involves soaking in hot water in deep bathtubs. Additionally, most Japanese houses have separate toilets and bathtubs. In winter, the temperature difference between the outside and inside of a bathroom causes acute illness, neuromodulated syncope and ultimately drowning.2 This tendency occurs more frequently in middle-aged and older individuals with a history of hypertension than in the younger population.
Older guidelines also consider ventilation essential for bystander cardiopulmonary resuscitation (BCPR) when drowning causes OHCA.3 However, the 2010 Cardiopulmonary Resuscitation Guidelines recommended the performance of compression-only BCPR (BCPR without ventilation) instead of conventional BCPR (a combination of chest compression and ventilation) for the untrained lay rescuer.4
In the case of adult OHCAs, the current guidelines recommend compression-only BCPR over conventional BCPR for untrained bystanders. Therefore, in this study, we evaluated the prognostic value of compression-only BCPR and conventional BCPR when drowning is the cause of cardiac arrest. We compared the differences in prognosis between patients with OHCA in Japan who received compression-only CPR and those who received conventional CPR between the older and younger generations, as well as between non-medical and medical OHCA.
Methods
Patient and public involvement
Patients or the public were not involved in our study’s design, conduct, reporting or dissemination plans.
Population and setting
As of 2016, Japan had a total population of 126.93 million (gender ratio: 61.77 million males and 65.16 million females; age groups: 15.78 million people aged 0–14 years, 76.56 million people aged 15–64 years and 34.59 million people aged≥65 years).5 Emergency medical service (EMS) personnel operate according to the protocols established by the Regional Medical Management Council based on the Japan Resuscitation Council Guidelines6; however, no established regulations have recommended the termination of resuscitation in the prehospital setting. Unless a patient with OHCA is dead (eg, decapitated) or shows postmortem changes, the EMS personnel continue resuscitation until arrival at the hospital. Paramedics are authorised to perform the following resuscitation procedures: use of airway adjuncts, including suprapharyngeal or laryngeal-mask airways, and peripheral venous infusion of Ringer’s lactate. Furthermore, authorised and specially trained paramedics are permitted to insert tracheal tubes and administer intravenous epinephrine.
Drowning is a process resulting in primary respiratory impairment from submersion/immersion in a liquid medium.7 Physicians, in collaboration with EMS personnel, judged whether drowning was a cause of OHCA in the cases reviewed in our study.
Data selection
The All-Japan Utstein-style OHCA Registry and the EMS transportation databases were obtained from the Fire and Disaster Management Agency (FDMA) with permission to analyse. Of the 504 561 OHCA cases whose data were collected by FDMA from 1 January 2016 to 31 December 2019, 16 376 (3.2%) were due to drowning. These cases were studied for epidemiologic analyses.
The FDMA’s All-Japan Utstein Registry contains data8 in the Utstein format. These data included patients’ sex, age, witness status, initial ECG rhythm, prehospital defibrillation status, prehospital physician involvement, critical time recording, 1-month survival after return of spontaneous circulation and cerebral performance category (CPC).9 To build a comprehensive database, the FDMA registry data were combined and coordinated with another EMS transportation database containing detailed information on the locations, time records and suspected drowning causes. Moreover, 268 participants with missing time records or discrepancies in data integration were excluded (online supplemental figure 1).
Supplemental material
Subgroups
The following two sets of subgroups were considered in this study: middle-aged and older (≥35 years) and younger generations (<35 years) and medical and non-medical. Age 35 years was considered the cut-off point when creating subgroups because the incidence of endogenous diseases such as cardiovascular disease increases at age 35 and above, known as the ‘coronary age’ worldwide.10 Non-medical drawing refers to obviously traumatic or struggling events leading to submersion in victims with no previous history of or in-hospital examination suggesting cardiovascular diseases. The exclusion of non-medical drowning was based on a diagnosis of medical drowning.
Outcome measures
The primary outcome was neurologically favourable 1-month survival, defined as a CPC score of 1 (good recovery) or 2 (moderate disability).
Statistical analysis
Patients who received BCPR were classified into no BCPR, compression-only BCPR and conventional BCPR groups. The epidemiological characteristics such as witness status, sex, season (summer, winter or others), age (≥35 years or <35 years), place (home or outdoor), shockable initial rhythm and prehospital defibrillation status were evaluated. Comparisons were made among the three BCPR groups. Nominal differences were assessed using the χ2 test. The crude and adjusted OR and 95% CIs were calculated. The null hypothesis was evaluated in each analysis at a two-sided significance level of p<0.05. Univariate analysis was performed to compare the epidemiology and characteristics of OHCA among patients who did not undergo BCPR, those who underwent compression-only BCPR and those who underwent conventional BCPR.
The outcomes of OHCA were compared using univariate and multivariate logistic regression analyses that included year term, age groups, gender, bystander-witnessed, shockable initial rhythm, any prehospital defibrillation and EMS response time interval. A repeat comparison of the most important characteristics of the compression-only and conventional BCPR groups was carried out after propensity score matching for several influencing factors, such as season, age groups, gender (sex), bystander-witnessed, dispatcher-assisted CPR instruction, shockable initial rhythm, any prehospital defibrillation and EMS response time interval, prehospital epinephrine administration, advance airway management and classification of the cause of drowning (non-medical or not). For propensity score matching, the calliper value and maximum allowable difference between matched individuals were set to 0.05. Subgroup analyses of the non-medical and medical, as well as middle-aged and older (>35 years) and younger generations’ cases, were performed before and after matching. All statistical analyses were performed using the JMP Pro V.17 software (SAS Institute, Cary, North Carolina, USA).
Results
Case selection
A comprehensive database of 16 376 OHCA cases presumably caused by drowning during the study period was subjected to epidemiologic analyses and then merged with the national and EMS transportation databases. After excluding those with unsuccessful binding or coordination (268) and whose arrest was witnessed by the EMS or physician (97), the remaining 16 108 patients were analysed to compare the epidemiology and characteristics of OHCA between middle-aged and older generations and younger generations. Additionally, after excluding those who received no prehospital resuscitation (100), 15 911 cases were subjected to the primary analyses. In total, 8507 patients (53.5%) had not undergone BCPR, whereas 7404 (46.5%) had undergone BCPR, including 6560 who received compression-only BCPR and 844 who received conventional BCPR. The patients receiving BCPR were subjected to propensity score matching (online supplemental figure 1).
Epidemiology of drowning-related OHCA
Drowning-related OHCA incidence was 3.1 and 3.3/100 000 population/year during 2016–2017 and 2018–2019, respectively. It occurred most frequently in the winter and least frequently in the summer. Most OHCAs occurred during the evening and night-time (17:00–0:59). The proportion of OHCAs due to drowning out of all OHCAs was higher during the weekend than during weekdays (p<0.01). It was also higher in females than in males (p<0.01). However, the incidence in the 100 000 population/year was higher in males than in females. The distributions of patients by age group were as follows: newborns, preschool children, schoolchildren, young adults, older adults and others. Most OHCAs due to drowning were older adults (>65 years) in Japan. In the southern area of Japan, unwitnessed OHCAs, non-shockable initial rhythms and no prehospital defibrillation were associated with higher incidences of drowning OHCAs across all OHCA incidences (online supplemental table 1).
Supplemental material
Comparisons of the epidemiology and characteristics of OHCA between younger and middle-aged and older generations
The epidemiology of OHCAs owing to drowning differed widely between younger and older generations. OHCA in younger generations occurred less frequently in bathrooms in the winter and more frequently in outdoor spaces in the summer. Moreover, its occurrence was more non-medical, and it was witnessed more by bystanders than that in middle-aged and older-generation OHCA. Furthermore, the incidences of BCPR, shockable rhythms and prehospital defibrillation were higher in young generation OHCA than in middle-aged and older-generation OHCA (online supplemental table 2).
Supplemental material
Comparisons of the characteristics and outcomes of OHCA between both groups with and without bystander CPR
The proportion of middle-aged and older-generation OHCA in the BCPR group was higher than that in the no BCPR group. Additionally, those of male OHCA, shockable initial rhythms, any prehospital defibrillation, prehospital epinephrine administration and advanced airway management in the BCPR group were higher than those in the no BCPR group. Furthermore, the EMS’ response time interval in the BCPR group was shorter than that in the no BCPR group. The BCPR group had better outcomes than did the no BCPR group (table 1). We confirmed the benefit of BCPR by applying multivariate logistic regression analysis including year term, age groups, gender, bystander-witnessed, shockable initial rhythm, any prehospital defibrillation and EMS response time interval: adjusted OR (95% CI) for 1-month survival and neurologically favourable survival with no bystander CPR as reference: 1.97 (1.39 to 2.79) and 3.28 (1.93 to 5.59), respectively.
Difference in characteristics and outcomes between two groups with and without bystander CPR
Comparisons of the epidemiology, characteristics and outcomes of OHCA between the compression-only and conventional BCPR groups before propensity score matching
Conventional BCPR was provided on drowning-related OHCA less frequently than compression-only BCPR (844 vs 6560 cases). Furthermore, the epidemiology, characteristics and outcomes of OHCA, including the season, age classification, sex, witness status, dispatcher-assisted CPR (DA-CPR) attempt, initial ECG rhythm and prehospital defibrillation varied widely between these two types of BCPR. The results were significant over the compression-only CPR group by focusing on bystander CPR, DA-CPR, initial ECG rhythm and prehospital defibrillation, with the following crude ORs (95% CI) based on compression alone: 1.56 (1.21 to 2.02), 1.61 (1.36 to 1.91), 2.84 (1.87 to 4.30) and 2.28 (1.67 to 3.10), respectively. Furthermore, OHCA cases receiving conventional BCPR were characterised by a lower incidence of DA-CPR attempts and higher incidences of arrest witnesses, shockable initial rhythms and prehospital defibrillation. Cases in the conventional BCPR group received prehospital epinephrine administration less frequently than did those in the no BCPR group: 0.80 (0.67 to 0.97). Outcomes of the conventional BCPR group were significantly better than those of the compression-only BCPR group (table 2). This superiority of conventional BCPR was confirmed by applying multivariate logistic regression analyses including year term, age groups, gender, bystander-witnessed, shockable initial rhythm any prehospital defibrillation, and EMS response time interval: adjusted OR (95% CI) for 1-month survival and neurologically favourable survival with conventional BCPR as a reference, 1.96 (1.31 to 2.92) and 3.17 (1.87 to 5.36), respectively.
Difference in characteristics and outcomes of two bystander CPR groups receiving compression-only and conventional BCPR: Before propensity score matching
The rate of neurologically favourable 1-month survival outcomes was compared between the subgroups using univariate analyses. It was significantly higher in the conventional BCPR group than in the compression-only BPR across all the subgroups. In multivariate logistic regression analyses, the differences between the two groups were significant in the younger generation and non-medical subgroups: 3.85 (1.22–12.2) and 3.20 (1.80–5.57), respectively. However, we could not prove the superiority of conventional BCPR in the middle and older generation or medical groups (table 3).
Subgroup comparisons of neurologically favourable survival between two bystander CPR groups before propensity score matching
Comparisons of the epidemiology, characteristics and neurologically favourable 1-month survival between the compression-only and conventional BCPR groups after propensity score matching
After propensity score matching, there were no significant differences in the epidemiology or characteristics of OHCA between the two groups, except in prehospital epinephrine administration. Its incidence was lower in the conventional BCPR group than in the compression-only group (online supplemental table 3). The neurologically favourable rates of the conventional BCPR were higher than those of the compression-only BCPR in terms of age (younger group) and cause of drowning (non-medical). However, there was no significant difference in the survival rate between conventional and compression-only groups (table 4).
Supplemental material
Subgroup comparisons of neurologically favourable survival between two bystander CPR groups after propensity score matching
Discussion
According to the WHO, drowning mainly affects children between the ages of 1 and 4 years, followed by children aged 5–9 years globally. Rivers and oceans are the most common locations for drowning.1 According to a survey on drowning in Japan, younger people are more likely to drown in the summer and have a higher incidence of drowning outdoors. By contrast, middle-aged and older people are more likely to drown in the winter and have a higher incidence of drowning indoors. The high incidence of drowning among the younger generation during the summer is attributed to their regular visits to bodies of water for leisure and other purposes during the season. However, the high number of indoor drownings in the winter among the middle-aged and older generation is thought to be because of the difference in temperature between the inside and outside of bathrooms, which causes a drop in blood pressure and increases the risks of strokes.11 12 This study was conducted considering these characteristics of drowning in Japan.
Previous studies have suggested that bystander-performed rescue breathing can be beneficial for OHCA of non-cardiac origin.13 However, a study by Fukuda et al reported no difference in good neurological survival within 1 month between the conventional and compression-only BCPR groups in patients who experienced drowning-related OHCA.14 It is important to note that this study did not provide data on the age groups and locations considered in the present study. Moreover, Fukuda et al found that BCPR for OHCA in children did not differ between conventional BCPR and compression-only BCPR.15 Conversely, Tobin et al reported that conventional CPR had a better neurological prognosis in paediatric drowning patients.16
The European Resuscitation Council Guidelines 2021 recommend the 15:2 ABC algorithm for paediatric basic life support providers.17 However, to date, studies have not considered the causes of drownings, which are the potential reasons for the relatively large number of matched older patients in this study. Therefore, this study examined the causes of drowning (non-medical or medical) besides the age classification.
Both multivariate logistic regression analysis before propensity score matching and univariate analysis after the matching disclosed no significant differences in the neurological favourable prognosis of OHCA in the middle-aged and older generation between the compression-only and conventional BCPR groups, while conventional BCPR improved neurological favourable prognosis in the younger generation. Furthermore, conventional BCPR showed an improved neurological favourable prognosis in the non-medical group; however, no difference was found for the medical group between compression-only and conventional BCPR. Based on these results, conventional BCPR should be performed in incidences of non-medical drowning in the young generation.
As part of the drowning process, the patient begins by holding his breath in the water. Laryngospasm might also be caused by fluid in the upper airway. As a result, the patient is unable to exchange air, and severe tissue hypoxemia develops.7 Furthermore, oxygen in the alveoli is wholly depleted during drowning. The patient suffers from hypoxic cardiac arrest in response. Conventional BCPR may be more effective for hypoxic cardiac arrest than compression-only BCPR. It is known that younger individuals who experience non-medical drowning suffer from hypoxic cardiac arrest. In such cases, conventional BCPR may have resulted in better neurological prognosis and 1-month survival results than that with compression-only BCPR. Conversely, middle-aged and older individuals may have underlying cardiovascular conditions that can lead to impaired consciousness and drowning, which could result in no significant advantage between conventional BCPR and compression-only BCPR.
It can be challenging to determine whether drowning is non-medical or medical if it occurs outside of the hospital; therefore, if possible, conventional BCPR should be performed on all patients. However, learning and maintaining ventilatory techniques can be difficult,18 and there are concerns regarding the risk of acquiring infections.19 20 Those reasons can be barriers to its practice. By contrast, compression-only BCPR is relatively easy to perform and allows civilians with no training experience to follow the dispatcher’s verbal instructions. Moreover, because of the current risk of acquiring infectious diseases, such as the coronavirus disease 2019 (COVID-19), most first-aid courses for the general public in Japan are now focused on teaching the practical method of delivering chest compressions and AED handling. However, ventilation procedures are not actively instructed.
The International Resuscitation Coordinating Committee recommends that trained civilians perform chest compressions and ventilation.21 Moreover, conventional BCPR is associated with better neurological outcomes for OHCA cases associated with younger generations and non-medical drownings. Based on these findings, it is recommended to enhance the availability of ventilation courses provided by fire departments and other organisations, the availability of which has currently decreased. This can allow an increased number of people in this patient group to receive appropriate ventilation, thus improving their neurological prognosis.
Study limitations
Among the OHCA cases in this study, data on cases presumed to be due to drowning were collected; however, the possibility that we included cases that were not caused by drowning cannot be ruled out. Moreover, similar seasonally focused studies are limited, and this field requires further exploration. Furthermore, EMS personnel interviewed bystanders to determine the factors associated with OHCA and performed the appropriate resuscitative efforts. However, reports from bystanders before EMS arrival and their contact with the patients could be potentially inaccurate. No established regulations have recommended the termination of resuscitation in the prehospital setting. Unless a patient with OHCA is dead or shows postmortem changes, the EMS personnel continue resuscitation until arrival at the hospital. Therefore, collecting data from other countries might provide different results. Additionally, the study did not examine the amounts of epinephrine administered or the time from OHCA onset to the initiation of resuscitation; these data might have affected our findings. Experience with BCPR training, social status, educational level and other extrinsic factors are factors that we did not examine, which may influence the association between BCPR type and favourable neurological outcomes. Moreover, the final outcome was determined at 1 month, but a longer follow-up (6 months or more) could have been performed.22 Finally, the current study was concluded at the end of 2019. Therefore, it did not examine the effects of the COVID-19 pandemic on the current BCPR standards about OHCA outcomes. This may be explored further in future studies.
Conclusion
Conventional BCPR yields a higher neurologically favourable survival rate than compression-only BCPR in patients with OHCA caused by drowning, especially if the patient is young or the case was non-medical. Conventional BCPR education should be provided to citizens who have the chance to witness drownings.
Data availability statement
Data are available in a public, open access repository. The data analysed in this study were subject to restrictions imposed by the Japanese Fire and Disaster Management Agency. Requests to access these datasets should be directed to the Fire and Disaster Management Agency, 1-2 Kasumigaseki 2-chome, Chiyoda-ku. Tokyo 100-8926, Japan (phone: +81-3-5253-5111; https://www.fdma.go.jp/en/post1.html).
Ethics statements
Patient consent for publication
Ethics approval
This study was approved by the ethics review committee of the Kanazawa Medical University (No. 1729). The requirement for written informed consent was waived owing to the anonymous nature of the data used.
Acknowledgments
We would like to thank the Fire and Disaster Management Agency of Japan for providing the necessary data. We would also like to thank Dr Masaru Sakurai from Kanazawa Medical University Hygiene for his guidance regarding the statistical evaluation performed in this study.
References
Supplementary materials
Supplementary Data
This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.
Footnotes
Contributors The corresponding author attests that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted. YK and HO had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. YK and HO had full responsibility for this paper and controlled the decision to publish. YK and HO equally contributed to this article as first authors. Study concept and design: YK, HO and HI. Acquisition, analysis and interpretation of data: All authors. Drafting of the manuscript: HI, TU, KN, TK, HO and YK. Clinical revision of the manuscript for important intellectual content: YK, HO and HI. Statistical analysis: YK, HO and HI. Obtained funding: None. Administrative, technical or material support: HI. Study supervision: HI.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.
Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.