The 2011 Defence and Security Winner - Frontline Oxygen

Frontline Oxygen: a portable concentrated oxygen source for injured soldiers

Cambridge Design Partnership, Centre for Defence Enterprise

When a soldier is injured in action, one of the first things he or she needs is oxygen. An injured soldier suffering from blood loss, shallow breathing or a weak pulse needs to be assisted with this valuable gas as quickly as possible in order to prevent hypoxia, which can lead to unconsciousness, coma or even death.

The period immediately following injury is known as the ’golden hour’, but getting concentrated oxygen to injured soldiers within this time has proved notoriously problematic for combat medics due to the size and weight of oxygen generators.

The demand for portable oxygen generators for the army has risen steeply since the UK’s involvement in Afghanistan and Iraq. The MoD would undoubtedly agree that improvised explosive devices (IEDs) have become one of the most significant threats to soldiers in these countries. The blast injuries they inflict can result in significant blood loss and, in addition, IED shockwaves can cause a condition known as blast lung, which inhibits a soldier’s oxygen uptake.

’Portable’ is the key word here. Getting concentrated oxygen to wounded soldiers in what are often hostile and inaccessible environments, such as half way up a craggy mountain or at the bottom of a muddy trench, presents a challenge that can’t be accomplished with large, heavy equipment.

Medics and doctors working on the frontline often have to evacuate the injured by helicopter, and these can take up to 30-60 minutes to arrive. Unfortunately, these are 30-60 minutes an IED victim might not be able to afford.

The need for highly portable oxygen concentrators on the frontline is clear and current systems aren’t adequate. This led Cambridge Design Partnership (CDP) to team up with the Centre for Defence Enterprise (CDE) and work on an alternative device.

The collaboration effort has led to the creation of an oxygen supply that to an injured soldier

Prof Stephen Lamb, the project leader at CDP, told The Engineer: ’Pressurised oxygen cylinders are too heavy and dangerous to use, while current oxygen concentrators are safe but rely on heavy batteries. As a result, there are obvious benefits to be achieved from designing a handheld, lightweight oxygen concentrator.’

The portable system can provide oxygen for several hours and weighs a mere 3kg; whereas the lightest cylinders weigh 4kg and only provide 20-30 minutes of oxygen and the largest cylinders can weigh up to 40kg. The weight of the batteries needed to power an equivalent system is roughly 11kg, Lamb claimed.

Moreover, the ballistic risk presented by cylinders is a major problem. The oxygen is pressurised to around 200 bar, which is a lethal amount of energy to be released if hit by shrapnel. Oxygen concentrators, by comparison, have a very low working pressure of approximately 1 bar, or atmospheric pressure.

The collaboration effort has led to the creation of a lightweight, portable and concentrated oxygen supply, which could be easily carried to an injured soldier.

So, how does an oxygen concentrator work? Most use a pressure-swing adsorption (PSA) principle. They contain two canisters of sand-like mineral called zeolite, whose particles are highly porous and can adsorb gases onto their very large surface area. The first canister is filled with pressurised air and the zeolite adsorbs the nitrogen while letting the oxygen pass through. After a few seconds, it becomes saturated with nitrogen; heating it up forces the nitrogen to desorb and regenerates the zeolite. While this happens, the second canister goes into adsorption mode. The pair of zeolite capsules continue to alternate and produce a constant flow of oxygen.

An innovative micro-diesel engine powers the oxygen generator and relies on the high energy density of diesel. Lamb told The Engineer earlier this year that a small amount of diesel could provide oxygen for four to five hours. He said batteries could have been used to deliver the required 100W to power the system, but they would not be able to provide the necessary longevity for the right weight.

To improve efficiency and reduce weight, the energy-intensive pump was linked directly to the micro-diesel engine, thus removing the need and weight of intermediate motors that are found in traditional oxygen concentrators. The engine also powers a relatively compact and lightweight generator, which provides the small amount of electrical power required by the system.

Through these cunning integration techniques, the micro-diesel engine allows the concentrator to take air from the atmosphere and strip out the nitrogen to produce 95 per cent pure oxygen.

In addition to the military setting, there is a need for portable oxygen concentrators in other areas where power is unreliable or deliveries of oxygen cylinders are not possible. For example, disaster-relief zones (such as those following earthquakes) and in countries where aid relief is needed.

Lamb claimed such a system also has the potential to support people who rely on oxygen on a daily basis as a result of a medical issue. He said: ’Portable oxygen concentrators for the civilian market are equally as limited by the weight of batteries so a lightweight alternative could provide benefits here as well.’

“Oxygen cylinders are dangerous to use, while current concentrators rely on heavy batteries”

PROF STEPHEN LAMB, CDP

This project has clearly demonstrated the CDE’s ability to act as a bridge between the MoD and industry, in order to help companies understand and tackle key defence challenges.

Since CDP had little experience of working with frontline soldiers, this relationship is central to the product development process. The £70,000 funding CDE contributed has also given the CDP engineers the financial backing they needed to produce the product.

The partnership also allowed CDP to access military personnel and equipment that were crucial to the development of the product.

Lamb explained: ’Access to the right people, such as medics, doctors, evacuation helicopter pilots and frontline soldiers was vital in order to understand their current equipment and working practices.’

The prototype version has been successfully tested in a lab environment and the next step is UK field trials to simulate the real-world environment.

So far, 7,500 coalition troops have been killed during the wars in Afghanistan and Iraq. IEDs are a growing threat and providing oxygen in hostile and challenging conditions where there is no power would be a fantastic step forward.