Blast injuries are often caused by more than one mechanism, do not occur in isolation, and typically elicit a secondary multi-system response. Research efforts often do not separate blast injuries caused by blast waves from those caused by blunt force trauma and other mechanisms. 15 experts from nine different NATO nations developed in the HFM Research Task Group (RTG; HFM-234 (RTG)) ‘Environmental Toxicology of Blast Exposures: Injury Metrics, Modelling, Methods and Standards’ Guidelines for Conducting Epidemiological Studies of Blast Injury. This paper describes these guidelines, which are intended to provide blast injury researchers and clinicians with a basic set of recommendations for blast injury epidemiological study design and data collection that need to be considered and described when conducting prospective longitudinal studies of blast injury.
- general medicine (see internal medicine)
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Blast injuries are often caused by more than one mechanism, do not occur in isolation, and typically elicit a secondary multisystem response. Research efforts often do not separate blast injuries caused by blast waves from those caused by blunt force trauma and other mechanisms. To add more complexity to elucidating blast injury pathophysiology, symptoms are often not immediately recognised or noticeable by a blast-exposed individual, especially when the individual is exposed to the blast waves but do not sustain blunt force trauma.1 Currently, limited data and evidence-based guidelines exist regarding complex, multisystem injuries associated with blast exposure. Epidemiological studies are critical for obtaining the necessary data to understand the mechanisms of injury caused by explosions, the response of an individual to a blast event as well as long-term effects of blast exposure.2 Data elements required to evaluate an individual’s response to blast exposure are summarised in Figure 1.
Fifteen experts from nine different NATO nations developed in the HFM Research Task Group (RTG; HFM-234 (RTG)) ‘environmental toxicology of blast exposures: injury metrics, modelling, methods and standards’ guidelines for conducting epidemiological studies of blast injury.3 These guidelines are intended to provide blast injury researchers and clinicians with a basic set of recommendations for blast injury epidemiological study design and data collection that need to be considered and described when conducting prospective longitudinal studies of blast injury. The objectives of this document are as follows.
To raise awareness with regard to the complexities and pitfalls of blast injury research.
To standardise and promote good research practices.
To help the community to generate valid and comparable results.
To increase the quality of publications in this field of research.
As per the HFM-234 (RTG) guidelines, a companion comprehensive ‘Dictionary of Blast Injury Research Terms’ has been developed by the NATO HFM-234 (RTG) and a shortened version of this has been published with this current paper.
Requirements for conducting a blast injury epidemiological study
A well-designed blast injury epidemiological study should include an exposure assessment, an exposed population and an unexposed population. Accurate blast exposure information is critical as this information is made part of the study and is used to determine health outcomes.4 The framework requirements for conducting a blast injury epidemiological study are similar to those found in Institute of Medicine (IOM) studies2 and other well-documented epidemiological protocols.
Prospective longitudinal studies for blast injury—study design
A prospective, longitudinal epidemiological study is often the best non-experimental means to confirm and quantify associations between exposure factors and health outcomes, although rigorous planning, coordination and cost factors must be considered. The ultimate goal of conducting blast injury studies is to elucidate the physical, biological and psychosocial mechanisms that cause blast injuries so that control measures can be implemented to prevent or reduce additional illness. A study needs to examine to some extent the progress and development of a potential disease or pathological factor or the response to blast.5
Alternatively, a retrospective study (eg, observational or phenomenological) involving data analysis based on medical history documentation can be used to identify certain components of importance if a full set of well-defined data exists for a focused hypothesis. However, researchers often still need to conduct a prospective study to control for variability in the study population, data collection protocols and data elements of interest to which registry data may not be focused. Accurate blast exposure information is critical; this information is made part of the study and is used to determine health outcomes.4 Efforts should be made to make the response to blast exposure as specific as possible.
The framework requirements for conducting a blast injury study are similar to those found in IOM studies and other well-documented epidemiological protocols. Following elements describe the required framework to conduct an epidemiological study and the specific requirements for executing a blast injury study.6
Well-defined research question.
Well-defined research plan.
Identifying biases and study limitations.
Data analysis plan: defining all variables and sample size requirements.
Documenting survey instruments and operational procedures.
Other potential considerations:
Banking of biological specimens.
Study population and sampling methods
The choice of the study population, including both the exposed and the control (ie, unexposed) groups, is a key factor in the design of a longitudinal study. The choice of study population affects not only operational aspects such as cost, administration and field operations but also may predict how applicable and what the overall impact of results may be. Further, the designation of the study population may lend itself to the choice of the control group, but the choice of the control group also has major ramifications on the aforementioned operational and impact aspects.7
Blast injury data collection
To determine and understand the aetiology associated with blast exposure, researchers should collect both initial exposure data, as well as data related to linking biological health outcomes to blast exposure. Parameters of interest to track initial exposure to blasts are described in Table 1. In addition, three broad categories have been identified as parameters of interest to track initial exposure to blast:
Characterising the threat itself, including the type and size of explosive, the exposure environment, and the distance and orientation of the service member from the threat.
Capturing information related to the individual affected by the threat as well as the scenario (eg, air sentry partly exposed, dismounted personnel kneeling down behind wall, and so on).
Capturing exposure measurements related to the threat.
In addition, researchers should determine the relationship of a pressure sensor to the exposure source. There is an increased emphasis on the need to characterise the side on and face on pressures (both amplitude and duration) of the blast. The shape and impulse of the pressure from a blast is a measure of the energy that can be transported. The first blast wave from an explosion is the only thing that can be measured in a defined way. If the wave is reflected, the origin of the blast really needs to be determined. Accurate measurements are not needed for high explosives that are lethal. For blasts in the 60–120 kPa range, small increases in amplitude can mean the difference between no injury and injury. Knowing the amplitudes and duration of a blast wave is crucial to determine its effect on the body. Furthermore, the distance from the blast is directly related to amplitude of the wave. Overall, the ability to accurately measure the intensity of blast waves in the 60–120 kPa range is needed to obtain quality correlations with the injury.
Data required to link biological health outcomes to blast exposure
Data linking biological outcomes to blast exposure must be captured in order to determine the response of an individual to a blast event, as well as determine what influences that response. To collect these data, researchers should build a predictive system that includes signal analysis and pattern recognition. Data should be captured on both the threat and the surrounding environment.
A chart showing linkages among the various categories of data that need to be collected in association with a blast event was previously presented in Figure 1, while key categories of data required to link biological outcome to blast exposure and whether or not these categories represent data that are intrinsically dynamic or static (or both) are summarised in Table 2.
Blast injury data management
Whether a prospective longitudinal study is implemented or a minimum set of data specifications is agreed on for data sharing between blast injury registries, guidelines for optimising existing databases can be implemented to standardise the quality and content of these databases.
Existing databases which function as blast registries were developed to meet government and other regulatory functions specific to that nation or organisation. Databases such as the Casualty Protective Equipment Analysis and the Joint Theatre Trauma Registry, as well as data collected with forms like the Military Acute Concussion Evaluation7 or data collected by existing programmes such as the Joint Trauma Analysis and Prevention of Injury in Combat may provide additional resources for researches in blast injury to conduct studies. Data in these existing sources range from mental health and personality traits to exposure and injury or casualty information.
Designate a data manager
Epidemiological studies and registries often involve multiple individuals gathering data at multiple sites. Therefore, data management is an important issue. The integrity of the data must be maintained and ensured by a qualified data manager, either the principal investigator or another individual to whom these responsibilities are assigned. The data manager will:
ensure adequate database specifications, security, structure and functionality;
prepare the data for the database (including, but not limited to ensuring adaptation of a protocol for de-identification of protected health information);
assess data quality through periodic review and mitigate all data quality issues;
assemble data for review and analysis.
Blast injury is a significant and complex problem facing military forces. The complexity of the injuries, particularly the multisystem response has made understanding blast injury aetiology very challenging. In addition, limited blast injury data poses a significant challenge for researchers. Development of these guideline represents a significant step forward towards gathering the appropriate data to understand blast injury aetiology and also highlights the value of facilitating a forum where multiple countries can share ideas and work together to solve an important health problem. To completely understand the nuances of blast injury aetiology, continued multinational exchanges of scientific information will be crucial for improving health outcomes associated with blast injuries.
This document provides researchers with a solid epidemiological framework and best practices to collect the appropriate data required to determine the response of an individual to blast exposure. These guidelines will benefit from their application and feedback to serve as a living guideline for future work in blast injury research. Although this document provides guidance on conducting blast injury epidemiological studies to collect and manage blast injury data, there is still a need to have more detailed discussions on the toxicology of blast, particularly toxicological methods and protocols relevant to understanding blast exposure effects. A concerted effort to bridge the fields of epidemiology and toxicology in a way that can impact and hopefully reduce burdens associated with blast injuries is imperative. Ultimately, to elucidate the biological mechanisms that cause blast injury pathophysiology, researchers need to have a solid toxicology framework as well. This framework needs to include at minimum, methods of understanding the dose, mechanism of the dosage and dose response endpoints of blast exposure (toxicology framework).
Lastly, these guidelines provide the minimum requirements to conduct a blast injury epidemiological study and do not represent an exhaustive list. Some of the framework elements may differ by country. Thus, researchers admonished to follow guidance and adhere to rules and regulations provided by their respective nations.
Funding H Orru work was supported by the Estonian Ministry of Defence under the project "Assessment and management of health risks among military personnel" and by the Estonian Ministry of Education and Research grant IUT34-17.
Competing interests The authors know of no known conflict of interest in the production and dissemination of this manuscript.
Patient consent Not required.
Provenance and peer review Commissioned; internally peer reviewed.
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