Feature 4 | PATROL AND RESCUE BOATS


High-speed boat impact injuries: a new test method


Johan and Carl Magnus Ullman explain the necessity of developing industry- wide parameters for impact exposure and a new test methodology to tackle common high-speed boat-related injuries


(Tis is an edited version of the paper “What impact exposure onboard high-speed boats is dangerous? International Multi-Agency Study”, authored by Johan and Carl Magnus Ullman for the International Symposium on Naval Medicine (ISNM) 2018).


Introduction Operating high-speed boats is dangerous: impact-induced injuries


can cause


permanent disabilities, and exposure to impacts is responsible for more injuries per workday than in most other peacetime work (1,2). However, it is NOT known which levels of impacts are dangerous and which are safe. Te purpose of this forthcoming study is to establish what levels and characteristics of impact exposure cause injuries. Current standards and regulations


lack relevance, because they are based on vibration standards. Vibration standards are based on mean values of vibration and not relevant for exposure to impact. Agencies in several countries, operating


high-speed boats, have expressed a wish to determine the severity of the impacts their personnel are being exposed to, and to what extent this exposure is dangerous. Some of these agencies also need to know what is relevant to measure and how to best collect and analyse the data. A new way of quantifying impact


exposure is needed. A new measuring unit, related to the forces challenging anatomical structures subjected to impact, needs to be defined. Data resulting from the study may lay the basis for a new relevant measuring unit based on the characteristics of impacts and correlated to injury risk. Exposure to whole body impacts has


significant physiological effects which cannot be measured by lab testing. In order to gather relevant data, it is necessary to monitor a large number of subjects, over a sufficient period of time, for exposure


44


It is still largely unknown which level of impacts is safe and which is dangerous


and a physiologic response indicating risk of injury. To achieve this, a joint effort is needed between international agencies operating high-speed boats in all kinds of missions and sea states.


Background In some countries, the EU directive 2002/44/EC (3) is applied to set limits for impact exposure. Tis directive is based on the ISO standard 2631:1 (4), which defines limits for exposure to continuous vibration but was never intended to apply to exposure to impacts. Te ISO standard is based on mean values of continuous vibration and contains


algorithms


quantifying energy transferred to the human body as vibration. Existing rules and standards are hence


not relevant for exposure to impacts onboard high-speed boats. The EU directive 2002/44/EC specifies: “Minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (vibration)” (sic!) Its defined exposure limits are legally


binding but impossible to comply with when performing SAR operations and military training. The exposure limits are defined in terms of mean values of vibration, not in any terms related to forces arising from exposure to severe impacts. In


most countries, this directive is not taken seriously. In some, much effort is focused on trying to comply with it, primarily by reducing exposure to vibration. The consensus within the scientific


community is that the currently applied vibration standards and directives are not relevant for quantifying risks of injury caused by exposure to impact (5,6). As there is no proven correlation between exposure to mean values of vibration and risk of acute injury, this use of the EU directive can potentially increase the risk of injuries caused by impacts (7).


Lab test drawbacks Various lab testing methods are being suggested and even proposed to replace sea trialling. Slamming impact exposure cannot be realistically simulated in a lab test. Real impact exposure is stochastic and multi-directional, reaching levels up to nearly 20g (8). For ethical reasons, humans cannot be exposed to the relevant impact levels in a lab. Suggested lab test methods have severe


limitations, making their results irrelevant for assessing risks of injury. Tese limitations include testing for impact and motion in only one, single axis, while the most dangerous exposure is multidirectional and stochastic, with significant variation


Ship & Boat International November/December 2018


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