Heat Causes More Than Stress

The Problem

The long-term question of effective heat injury prevention as well as post operational rehabilitation has produced many scientific as well as not so scientific answers. The easy answer to heat injury is to cool off the body and the problem goes away. This in itself raises more questions than answers. How do we cool the body? By what means do we cool? At what rate can the body tolerate cooling? Based on severity of the “injury” are there different means of treatment? The U.S. Special Operations Command (USSOCOM) has put a significant amount of money into answering these questions, and has finally gotten some good data. Please keep in mind that while this information is derived from a military/tactical environment, its application is equally relevant to the fire service with regards to firefighter rehab, law enforcement and daily armor wear, as well as EMS and heat injuries in the summer time. More deaths are caused each year by heat stress than by hurricanes, lightning, tornadoes, floods and earthquakes combined, with an average of 1,300 deaths annually. This is a general number, with higher percentages in the public safety and military community.

There are three general classifications of heat injury. While heat rash, edema and tetany exist, for the purposes of this article they will not be explained much further due to the generally minor impact they have on systemic functioning. Heat cramps are the first of the heat related injuries we will look at. This originates most commonly in the calf muscles and is identified by involuntary muscle contractions, after physical activity. This is much like the Vibralert® in an Air-Pak®, it’s the warning sign prior to progression of injury. It is caused by a failure to replace sodium (salt) in the body after sweating. It is an electrolyte imbalance. Heat exhaustion is the progression of heat injuries, and manifests as a somewhat “drunken” appearance. Weakness, unsteady gait (walk), fatigue, dizziness, headache, nausea and even collapse.  This is caused by prolonged factors that also cause heat cramps with the addition of “heat strain” from inadequate water intake. The body’s cardiovascular system can’t keep up with demand and has begun to “strain” the heart. The heart is beating much faster than needed. While this is a compensation mechanism, it has its faults. The heart’s rate and ability to fill completely are directly related. Heart rate increases, this reduces the time for the heart to be able to fill, effectively reducing the amount of output by the heart or (CO, not carbon monoxide, but rather cardiac output). This mixed with blood pooling, because of the ineffective flow, can lead to heat stroke if untreated.

Heat stroke is a potentially life threatening condition, diagnosed by a core temperature greater than 105°F. At this temperature the body is unable to effectively function at the cellular level, much like a large factory where the air conditioning has stopped or the fans turned off. Workers will eventually refuse to work effectively in those conditions and begin to pass out or quit. The hypothalamus often begins to become overwhelmed and is no longer able to effectively regulate temperature within the body. This leads to a runaway train of worsening symptoms. The treatment for this is to apply rapid cooling, and cool the body to less than 102°F, however there is the possibility for cooling too quickly after initial lowering of temperature. Shock must be assessed for and treated.

With the basic understanding of the conditions that can manifest from excess heat, be mindful that the wear of armor has a significant impact on your body’s internal heat regulation mechanisms. The body relies very much on convection to cool; when your core is encapsulated in an armored vest it is unable to use this mechanism to remove heat. It actually retains heat, increasing the incidence of heat related injury. However, coupled with the extreme temperatures of modern conflict areas, rehydration is insufficient. Operators working at even moderate levels produce 2L/hour of sweat as their bodies work to keep core temperature from elevating, while exercise research has shown water intake rates of greater than 0.5L/hour are unsustainable. As dehydration of even two percent of body weight substantially reduces performance, operators naturally reduce their work output. Quartermaster guidelines show that moving from hot to temperate conditions lowers recommended soldier water requirements by up to 50 percent.

The Solution

The holy grail of a “solution” has long been sought after. All of the science that was cited above has generated data that lead to much of the technical innovation in the field. SOCOM has found that 140 watts off cooling was needed to effectively maintain operational capabilities in operators wearing armor. That is correct: watts, like what you see on lightbulb. The watt is a unit that quantifies the transfer of energy; one watt is equivalent to one joule per second.  So the body needs help to maintain its internal cooling efforts, especially in armor. Up until now the millions of dollars of research has led to development of expensive, heavy, powered devices. Many of your departments may own “cooling vests” for rehab, or other forms of powered cooling. These items are great in the setting of rehabilitation where power is readily available. However in an operational setting where mobile power is extremely resource intensive or non-existent, cooling vests are impractical. Additionally, they lack the power and duration desired by end-users. On the fire ground they can be used as a means of rehab that doesn’t need cooling. The Qore Performance IcePlate (pictured) answers the call for the power and duration desired by end-users combined in a lightweight and deployable package.

This novel product has now created a means to reduce the rate of core temperature escalation, as well as offering a hydration-carrying platform as the ice melts. The “generator” of this product is water, or rather ice initially. Water is what is known as a phase change material (PCM). PCMs are substances that have a high heat of fusion, which melting or solidifying at a certain temperature is able to store or release a large amount of energy. With the knowledge from the military of needing a minimum of 140 watts of energy to effect cooling, the IcePlate was developed to answer the call. The low cube of the product, and use of a cost effective and consumable PCM makes for an incredible game changer in the field of heat mitigation for the operator or any public safety professional.

A few of the ways this has changed the game starts with the ability to now reduce weight and cube of the water you carry. Hopefully everyone wears a hydration bladder or carries some water with them on operations. This now takes that and stores 100 ounces of water in a one-inch thick reservoir that serves multiple purposes. It also has been proven to decrease the backface defacement of armor plates when struck by multiple types of rounds. The IcePlate is able to function in multiple capacities for the operator, as well as offer an improvement in armor kit ergonomics. The low profile of the plate is a huge additive to its already attractive capabilities. So the ability to generate 140 plus watts of cooling for a minimum of two hours in warm climates, meets the need for improvement in operator capability. This has been proven to reduce the water intake need by almost 50 percent. The plate itself also creates a layer of condensation in the wearer’s shirt or between the plate and skin. This effectively acts as another mechanism of conductive heat loss mitigation — minimizing water loss through sweat.

Moving into the future there is an absolute need for products like this. With a price point of less than $80 per set it is a no brainer for any operator, and should be considered in the fire service as a cooling vest substitute. These plates can be worn as a standalone “Vest” by routing straps through the top loops of the IcePlate, then allowing the firefighter to wear during rehab. The plates are intentionally designed to be placed into a Pelican Cooler (pictured)

The plate is made to fit a wide variety of plate carriers, armored vests, and “Heavy Vests.”

Photo courtesy of SOARescue

This allows for the plates to be “charged” in the freezer and removed and placed in a cooler for an extended period of time while they remain charged and ready for rehab. This wide adaptability has made this one of the most significant tools developed for the minimization of heat injuries, and should be considered as an incredible addition to your kit, or rehab policy.