Wearable sensors for monitoring heat stress

Wearable sensors hold much promise as a way to better manage first-responders’ health and comfort while working in hot or dangerous environments
Wearable sensors for monitoring heat stress

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The invaluable work done by first-responders can put great demand on their bodies and can often require them to trade their own safety for that of the general public. While training, equipment and procedures help to reduce the dangers, the element of risk cannot be completely removed. At the same time, the weight and heat-retaining nature of personal protective equipment (PPE) means that many first-responders can easily overheat. For these reasons, there is growing interest in systems that can report wearers’ vital signs both in real time and for post-incident analysis.

Two companies that are active in this area are Equivital and Bodytrak. Anmol Sood, CEO of Equivital, says a recent study reported that prolonged long-term exposure to heat could lead to cardiac issues, when previously it was thought that immediate exposure to heat stress was the risk factor. “The safety argument is similar to American Football. While the collisions that players have in a single game may not lead to an injury, the result of impacts over many years can cause cumulative neurological damage and even mental health problems. We believe firefighters need to have their heat risk monitored on every exposure and this should be managed over time by the occupational health and safety team.”

Turning to police forces, Alec Creighton, head of business development at Bodytrak, says at a recent Home Office Centre for Applied Science and Technology (CAST) event, the centre “put forward very clear requirements for wearable technology for monitoring and it gave two examples. One was Notting Hill Carnival, where police officers work 12-hour shifts while kitted out in full PPE, so understanding which are suffering from heat stress, dehydration or fatigue would be critical. “The Police Service of Northern Ireland also spoke at that event, specifically around when its police officers are in full riot gear. During the summer months it’s extremely hot. Even if the police officers aren’t on the street they’ll be sitting in a van up to an hour.”

Steve Beach, sales director, EMEA software enterprise at Motorola Solutions, says wearable sensors could help improve response times and the handling of incidents when first-responders are in harm’s way. For example, if an officer’s heart rate becomes elevated, sensors could be linked to a body-worn camera and programmed to automatically activate recording or streaming from the device and/or activate the emergency button on their two-way radio. This approach would allow the officer to focus on dealing with the issue at hand.

Creighton adds that one other role that wearable sensors could play is in aiding medical personnel in remote diagnosis so they can provide advice to someone near the casualty during “the golden hour” – the time between receiving the injury and getting into hospital. “We’ve started some pilot medical trials, so the later editions of Bodytrak would allow medical professionals to look at those vital signs and be able to make initial diagnosis in an emergency situation and perhaps also with long-term chronic diseases.”

Another sector where it might make sense to monitor vital signs is transport, given that in the UK, the most common cause of fatal industrial accidents is being struck by a vehicle.

The nuts and bolts 

Equivital’s main offering in this area is Black Ghost, a system that focuses on heat stress, safety and performance monitoring; it uses the company’s EQ02+ LifeMonitor wearable sensor, which has an 8Gb SD card for data storage and a Bluetooth module that allows data to be sent in real time to a communications device such as a smartphone or TETRA radio, which can send the data back to either a cloud-hosted server or the organisation’s own server.

“Our systems are integrated with certain public safety radios already. We work with TETRA manufacturers to deploy dedicated TETRA networks at customer sites so that our data can be transmitted in real time,” says Sood.

Bodytrak has taken a similar approach: “We don’t have the radio capability in our device, we connect to another device that does that,” says Richard Collins, Bodytrak’s head of product. “We want to work across the big manufacturers of those devices, we act as a peripheral to them. They can use the Bodytrak earpiece to support and control two-way communications while the earpiece is running as a physiological sensor solution.” The Bodytrak device also has onboard flash storage and the data it generates is sufficiently small for it to be transmitted over a DMR network.

When firefighters are kitted out in full PPE and in hot environments, Collins says that this “makes it difficult to wear things such as chest-worn devices or wrist straps, mainly because they’re measuring skin temperature and not referencing core body temperature”.

Equivital’s Black Ghost system allows users to set upper and lower thresholds for body temperature, heart and breathing rate and combines this with a red/amber/green alert index. Sood says the system can also help quantify optimal work/rest cycles for those professional teams who depend on this. In addition, “we are looking at monitoring both physical and emotional stress in the future”.

Similarly, Bodytrak’s Collins says: “We’re able to process the data and provide red, amber and green alerts that are very easy to understand and see and [allow incident commanders to] make very easy interventions without having to have a medical person present to help them with [interpreting the data]. If someone were to show clear signs of heat stress, we would portray that as an orange marker and then the commanding officer could allocate his resources appropriately.”

Sood adds that Equivital Black Ghost is being used by HARTs (hazardous area response teams) – paramedics and first-responders working with the NHS who are sent to incidents that may involve hazardous or toxic material. “We’re [also] in use by various divisions within the US DoD and other public safety organisations. In addition we work with a number of oil and gas companies and nuclear safety organisations. We’re currently conducting multiple pilots and research studies with firefighters and fire and rescue services.”

Comfort versus accuracy 

Sood notes that one of Equivital’s focuses over the past 10 years has been to eliminate the trade-off between sensor accuracy and user comfort ­– “we’ve come up with a good basis to have an accurate reliable sensor that is still comfortable to wear for long periods of intensive use” – and this has been underpinned by trials and testing.

Equivital has also worked hard to make the system as accurate as possible. “With a lot of sensors out there, if they have any poor-quality data, they don’t do anything intelligent with it, they just throw it away and try and look at the next good data point. We have some very smart signal and noise filtering algorithms and intelligence within our system that allows us to get the maximum amount of accurate data during periods of noise. We have confidence levels within our system – every sensor at some point is not going to give you accurate data, especially in an ambulatory environment. Confidence intervals are overall indicators for the data accuracy.

“One of the big things that we have to overcome is that in the environments we work in, people get very hot and perspire and the saline in the sweat can interfere with some of the noise and some of the signals that we’re trying to acquire. So we have had to develop technologies within the platform that can protect the system from human perspiration.”

Sood adds: “We have evidence-based data to back up [our claims on accuracy] as well as regulatory clearances. The EQ02+ LifeMonitor is FDA510K-cleared, so we’ve had to monitor and measure ourselves against clinical-grade, gold-standard data. We’re also the world’s only ATEX and intrinsically approved wearable sensor.”

Bodytrak’s Collins says: “Our product is designed with high grade materials to ensure it is physically robust and to prevent saline in sweat from degrading the casing or compromising the circuitry and the device’s inner workings, all of which could lead to inaccurate measurements. It’s about making sure we manufacture with materials that underpin and protect the mechanical design, and which will stand up to the type of use we expect from our users who will largely be working in fairly extreme environments. We will also be certifying the device as ATEX compliant.

Equivital’s Black Ghost has an interface that allows it to “easily” integrate with external sensors, and Sood says this allows environmental data such as pollution, noise, gas detection, video and weather data to be added, and these external sensors don’t have to come from Equivital. “We will partner with companies who already have sensor technology out there, but we can bring it into our platform, aggregate it with Black Ghost data and then provide complete situational awareness for human heat stress, safety and performance monitoring.”

Collins says Bodytrak has designed its offering for easy integration in the form of “a range of cloud capabilities and API specifications” so that the relevant data can be directly relayed to the customer’s incident management centre in whatever format they require. “That takes our development slightly away from just being an embedded wearable to something that needs to be very cloud-centric.”

I was blind but now I see 

One piece of wearable technology that has recently made a splash in the public safety space is Qwake Technologies’ C-Thru, a real-time augmented thermal computer vision system that makes it easier for firefighters to see in smoke-filled zero-visibility environments. It can also wirelessly stream the footage back to incident command together with the user’s location.

Qwake Technologies performed a field study in February with the aid of four engine units from the Menlo Park Fire Department in California. The firefighters were tasked with finding a hidden ‘victim’ – a fire cadet with an oxygen tank – using either C-Thru, a handheld thermal camera, or some in-mask thermal displays from other manufacturers. According to John Long, Qwake Technologies’ co-founder, the latter are hands-free “but the display is down towards the bridge of the nose, requiring that you divert your visual attention”. The eight firefighters ran three routes, each using a different technology. According to the company, the firefighters using C-Thru found the target in 1.6 minutes, 267 per cent faster than the 4.5 minutes required when using its closest equivalent, and there was a three-fold increase in consistency, despite the firefighters having “zero training” with C-Thru.

Long adds: “The next test and validations we need to do require hardening the equipment so that it can be durable in a range of fire scenarios – that’s what requires us to partner with an OEM [original equipment manufacturer] in this space that already makes firefighter masks. We’re in talks with two [such companies], which are interested in C-Thru, and we’re also raising some outside capital to basically keep [body] and soul together over the probably two-year period that it will take to produce the final product.”

He says biometric capabilities are on C-Thru’s product roadmap and this is one of the areas where it is seeking to collaborate with OEMs, and “one big difference between C-Thru and the existing products on the fire protection market is we intend to use essentially a small form factor but fairly powerful computer on the first-responder, which makes biometrics integration fairly straightforward”.

Qwake Technologies is particularly interested in combining this with Wi-Fi so that if multiple firefighters are on the scene, they could be aware of each other’s readings when they are close to each other, so that, for example, if one of them fails to notice that their O2 tank is running low, one of their colleagues can alert them to the issue.

One synergy between thermal cameras and biometrics would be to aid the prediction of heat stress. Long says “you can get a sense of the ambient air temperature from a thermal camera – it can tell you if you’re walking into an oven, where the ambient thermal radiation exceeds what is safe for a first-responder”. He adds that there are a lot of caveats in this regard, particularly when trying to use thermal imaging to determine whether or not surfaces

are safe to touch. He says some firefighters have died while relying on the readings from thermal cameras due to the problem of emissivity – the relationship between an object’s heat and the amount of infrared it emits depends on a number of factors and can be significantly less than 1:1.

He says: “We’re examining this point, particularly with radiometric thermal cameras that give you absolute temperature measurements, but our emphasis has been on using the capabilities of thermal cameras to see through particulates [and in the dark] to aid in navigation. Beyond that, we’re looking into it but we’re taking very cautious steps, because the history of using thermal for navigation purposes has been pretty much all positive, but using it for actual temperature gauges has been quite mixed.

“My approach as a neuroscientist would be to maybe have a set of learnt thresholds where the processing on the system gives you some colour coding and basic warnings – you never want to take the judgement of the first-responder out of the scenario.”

We have seen that there are clear use-cases for wearable sensors in a public safety context, the technology is mature and is well tested, while innovation in related areas offers significant synergies. Where the technology goes from here is anybody’s guess, but it’s certainly one we’ll be watching with interest.

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