Defence Codex - The journal for defence engineering & science

Fire and ice

Survival put to the test

Military operations frequently take place in harsh environments, pushing the human body to the limits of endurance. Extreme heat and cold are faced by troops deployed to areas around the globe – as part of operations, in pursuit of peace, or providing humanitarian aid – and climatic injuries continue to account for a significant proportion of non-battle injuries reported in theatre. Codex investigates the research that is being done to understand the stress and mitigate the effects of surviving harsh environmental conditions.

The human body is only able to tolerate small variations in its temperature and through a complex mechanism of thermoregulation maintains core body temperature by releasing or retaining heat. If the balance is disrupted by external factors (such as exposure to extreme heat or cold) then injury, illness or death may result.

When the body is cold, heat is conserved by vascular adjustments which draw the blood away from the skin to the body’s core. This is followed by shivering – which contributes metabolic heat – and the release of hormones which elevate resting metabolism. Hypothermia occurs when the body core temperature drops to 35°C or below.

Severe hypothermia may be caused by prolonged exposure in freezing conditions due to a fall, avalanche, entrapment or submersion in water. Conditions resulting from exposure to freezing cold include frostnip and frostbite.

In heat stress, warm blood is sent from the core to the skin where heat is lost through radiation, conduction, convection and evaporation. At high temperatures and during exercise evaporation is the major physiological defence against overheating. Humidity greatly reduces the effects of evaporation and there is greater risk of dehydration and heat related illness. With severe heat stress an unchecked rise in temperature (hyperthermia) can result in organ failure and death.

Heat illness also has a wide range of other symptoms, ranging from cramps to heat stroke and typically affects young athletes or military personnel who are unable to lose the heat quickly enough that is built up in physical exertion in extreme heat.

For over 50 years defence scientists in research establishments, and more recently Dstl and QinetiQ, have been researching the impact of thermal stress on members of the Armed Forces. Current operations have required field and laboratory based studies concentrating on the problems created by heat stress and searching for ways to help protect and maintain operational effectiveness.

QinetiQ, Human Protection & Performance Enhancement Operations Manager, Simon Wickes is stimulated by the challenge of Human Science and its application: “Human Science is an area that is constantly changing; the environment, the equipment, the application and the human, all contribute to changing requirements and challenges. It is this that makes the work so interesting. The range and variety of work we do means that the programmes and projects we undertake can change from one week to the next. Also, the opportunity to work with different subject populations, from top sportsmen and women to helping the people who protect our country gives a sense of achievement.”

MOD funded research has resulted in proposals for heat stress limits, in terms of temperature and humidity, which are used to inform risk assessments for heat illness. QinetiQ scientists have also been trying to find out how much acclimatisation UK personnel need when deployed, or returning to, hot-weather operations after rest periods at home. One outcome of this work is to question whether optimal heat acclimatisation could be obtained by using ‘staging camps’ such as Cyprus which is typically warmer than the UK, but not as hot as the continental Middle East.

In the air domain, QinetiQ qualified the liquid conditioned garments worn by Eurofighter Typhoon pilots and have evaluated the requirements and potential solutions for personal cooling solutions for helicopter crews operating in the Middle East.

Most of the research takes place in QinetiQ’s four Environmental Chambers at Farnborough and Boscombe Down where they are able to accommodate an aircraft, several vehicles or even a complete rail carriage. The climatic chambers at Farnborough are able to simulate environments between -20ºC and 50ºC, with controlled humidity, solar radiation up to 1000 Wm-2 and air speeds up to 10ms-1 whereas the Environmental Test Facility at Boscombe can extend these parameters to between -70ºC and 80ºC.

Wickes believes that the chambers are key tools in managing the risk of exposure as they offer flexible test facilities for human studies and the assessment of personal protection equipment in a wide range of controlled environments.

Whilst used primarily for defence work, the chamber has also undertaken work for the England Women’s Hockey Team, who used the facility to acclimatise their players for Southern Europe for the World Championships; Formula One driver and commentator, Martin Brundle who wanted to educate television viewers on thermal load relating to motor racing, and recently for assessing thermal characteristics of new protective clothing.

MOD and QinetiQ are also looking at other areas that affects troops in meeting the demands of harsh environments including:

• laboratory and field testing to help determine the next generation of clothing and equipment for UK land forces;
• working alongside the Defence Food Services team to review the Operational Ration Packs to provide components that meet the nutritional requirements needed in theatre including hot weather supplements as ell as palatability to reduce wastage;
• investigating the problem of how individuals react differently to thermal stress and whether the basis for these differences include any genetic links;
• smaller, lighter sources of energy to support new technological cooling solutions; and
• improving equipment efficiency and protection to meet the needs of aircrew.

Dstl – experts in human performance

MOD research has for many decades advanced scientific knowledge in human survivability and performance in environmental extremes. Today, Defence Science and Technology Laboratory (Dstl) continues to investigate and provide advice on every aspect of human performance, including the effects of climatic injuries such as hyper (heat strain) and hypothermia (cold strain).

Dstl uses a climatic chamber to recreate heat and cold stress and wind to test equipment, clothing and behavioural strategies. Their aim is to understand and to mitigate climatic stress and research novel ideas to protect the UK Armed Forces.

Human volunteers and mannequins that mimic human responses are used to validate predictions derived from mathematical modelling. The results of Dstl research inform MOD policies and contribute to saving lives in theatre.

Dstl Principal Scientist, Human Systems Group, Rene Nevola is a biomechanist and physiologist based at Porton Down. He was the author of “The Commander’s Guide to Potable Fluid Intake” and he investigates environmental stress and advises MOD and the British Olympic Association on acclimatisation strategies and physical training in hot environments.

“The chamber provides excellent testing facilities and in addition means we can assess the performance effects of novel strategies that may have military value during extremes of heat and exercise,” explains Nevola.

Nevola has certainly pushed himself to extremes; in 1993 he became the first Briton to run across the Sahara desert and in 2002 the first to run unaided along the length of Qatar. The view in the chamber may not be as inspiring, but he is able to understand how visitors to the chamber feel during testing and is keen to emphasise that they have the approval of MOD’s Research Ethics Committee (which is required for research involving human participants undertaken that is funded, or sponsored by the MOD): “We make sure that the physiological responses of volunteers are safely monitored and the data enables scientists to provide accurate and timely advice responding to Urgent Operational Requirements (UORs) as well as reach-back requests for information from Dstl’s Scientific Advisers based in front line operations.”

As an exercise physiologist, his earlier work concentrated on the effects of cold stress on military performance helping to shape operational advice and equipment requirements for personnel operating in Arctic climates. “Volunteers dressed in arctic combat clothing were exposed for six hours to dry-bulb air temperatures of 5°C. They were sprayed with water every 40 minutes during a slow walk into a head wind.”

Follow on studies have looked at nutritional status and its relationship to shivering which produces body heat. Another study looked at the consumption of a combined dose of caffeine and ephedrine (a stimulant) in order to investigate any potential benefits in delaying hypothermia. Nevola fully understands the demands of testing and admires those who support their work in this way: “As a volunteer myself, I have gained a healthy respect for my military colleagues and the stress to which they are often subjected to in training and operations.”

Today, military operations are increasingly conducted in hot environments and require research into equipment as well as into heat illness and injury. Nevola has done his share of research in the field and has visited the deserts of the Sahara and Qatar as well as Kenya and Sabah. He has also been involved in NATO task groups which have led to collaboration in remote physiological monitoring of personnel in extreme environments.

Dstl’s recent work has looked at combat body armour and the cooling systems and protective garments for aircrew. Their research into textiles, which is an important part of thermal regulation, has informed the development of military clothing and equipment including sleeping bags. Another area where Dstl facilities have value is in training and updating military skills to deal with injuries in these areas.

Nevola is keen to stress that their work covers all environmental factors, not just heat and cold: “Past military campaigns have been impacted by heat, cold, altitude, as well as the changes in barometric pressure that divers face in special operations. Cold stress poses considerable threat to the well-being and physical and cognitive performance of military personnel who serve in climates with low environmental temperatures. The effects of altitude as experienced in mountain terrain also needs to be investigated in combination with exposure to extreme ambient temperatures.”

The customer driven work that Dstl undertakes makes a real difference to operations and other customers. Summing up, Nevola concludes:” The requirements are genuine. An Urgent Operational Requirement may suddenly arrive, requiring team effort to deliver results. Dstl enables me to be part of the solution that saves lives. That excites me,”

The UK Armed Forces, explorers and adventurers can be assured that Dstl will continue to support them in operations, explorations and adventures.

See also: Journals P66 Water Intake and Urine Output by joint author Rene Nevola.

www.dstl.gov.uk