Why Does a Diver Need a Heater?

Unless the water temperature is greater than 90º F, you will lose heat. The human body must maintain a constant core temperature for efficient metabolism. Even a minor drop of only a degree or two can cause some adverse effects. Our body’s response to decreased core temperature is a complex process. A diver experiencing “mild” hypothermia will feel cold, most noticeably in the extremities. Also common is an accelerated heart rate and increased urge to urinate.

Vasoconstriction (narrowing of the blood vessels) will shift the blood from the periphery into the core, which is interpreted by the body as a state of over-hydration. The brain shuts off production of antidiuretic hormones, causing the diver urinate frequently. As the urine is at body temperature, significant heat is lost along with the fluid output. Shivering usually occurs as an early symptom only if the diver isn’t vigorously swimming or is not engaged in other physical activity. That means the diver can delay shivering or completely suppress it depending on activity.

When we’re exposed to cold on land, an effective way to warm up is by exercising. As you know, even on the coldest days, you can exercise to a point where you perspire. Some assume that these techniques can work well underwater. Unfortunately, that’s not the case. While increased exercise may make you feel warmer, it masks what’s actually happening to your body. Increased exercise does increase heat production, but the water drains the heat away faster than you can produce it. So the net effect of trying to warm up by vigorous swimming is merely to increase the amount of heat lost. The inevitable outcome of this practice is a cold and tired diver with shorter than otherwise bottom time.

Scientists have demonstrated that nitrogen narcosis can inhibit the shivering response, eliminating an important warning sign of hypothermia.

Most divers assume that only “northern divers” need to worry about heat loss; tropical divers have nothing to worry about. In reality, understanding heat loss is critical to all divers, because of a phenomenon known as warm-water or undetected hypothermia. Unlike in cold water, heat loss in warm water is slow and gradual. This long, slow cooling of the body can significantly lower core temperature. The phenomenon has been documented in divers engaging in diving for several days in temperatures as high as 81º F without long periods of rest between dives ---a typical scenario for a diving vacation. Under these circumstances, the skin temperature remains within comfort range, while the core temperature slowly and insidiously drops over time. The most common symptoms of undetected hypothermia are fatigue, loss of motivation and impaired mental ability. The research has indicated that this form of cooling may not stimulate shivering until the diver is significantly hypothermic.

Upon immersion, a diver begins loosing heat by conduction. Even in the full 7mm wet suit, heat loss can be accelerated by water flushing trough the suit due to vigorous swimming or improper fit. On descend, the wet suit compresses and loses its effectiveness. On a deep dive, the 7mm wet suit might only provide the protection of a 3mm suit. A dry suit offers better protection; however, it also has its limitations. It uses air as an insulator, which is trapped in the undergarment. The otherwise fluffy undergarment will be also compressed by the water pressure, thus losing its full effectiveness. Adding more air into the suit to increase the airspace between the suit and the skin will only create a bubble at the highest point of the suit. If the diver could wear a more rigid undergarment, which would not compress as easily, he would then be excessively buoyant, requiring enormous weight to descend. The wet suit diver could increase the suit thickness, but besides losing his mobility he would face the same dilemma trying to descent.

The diving suit manufacturers have reached a dead end in the development of PASSIVE THERMAL PROTECTION SYSTEMS. Regardless of the effectiveness of any exposure suit, no suit used by sport divers can stop heat loss. At best, even the most expensive suit can only slow the process. With the introduction of rebreathers, mixed gases, underwater propulsion vehicles etc. our bottom times have increased. However, the bottom time, until now, has always been limited by the EXPOSURE TIME. Not anymore!

A big breakthrough in diving:
ACTIVE THERMAL PROTECTION SYSTEM

PATCO Inc. is the leader and innovator in wet and dry suit heaters. As you now know, the only way to keep warm while diving is with supplemental heat. The diver simply takes the heat with him on the dive. All he will do is basically remove a portion of the lead weight from his weight belt (which only provides gravity) and substitute it with an energy source. The lead weight is in the form of a battery pack. The only difference is that instead putting it back on the weight belt, it is attached to a scuba tank. It provides an energy, which keeps the diver warm in all diving conditions. Supplemental heat is the future of diving. AQUA HEAT was designed not only for diving, but other sport activities as well, such as hunting, motorcycle riding, snowmobiling, camping and even skiing. You can take it to the ball game or use it while working on your car. Its use is limited only by your imagination.

The future is even more exciting. As the battery packs decrease in size and increase in capacity with newly emerging technology, diving will be changed forever. Can you imagine a 3mm fully heated suit, powered by an energy pack that fits inside the BCD pocket, with a dial to select a comfort level for the entire dive trip? You won’t have to worry about cold water, wind or thermo clines. We are not there yet but such wonders may be available in the near future.

The conclusion from this discussion is clear. Unless the water temperature is above 90ºF, the question isn’t whether or not you are losing heat; it’s how much you are losing. We rate the core temperature on a scale from zero to ten. At ten you are fully regenerated. One more point and you will start sweating. If you reach zero, you have lost so much heat that you will start shivering. As you learned previously, the shivering point will be delayed unless the diver is motionless. If the diver’s core temperature is anywhere between one and ten, he will not have any symptoms of being cold.

If you are ten before jumping into water, you will have a great advantage over divers who are, let’s say, five or even three. Your core temperature will drop, but hopefully, you will finish your dive before it drops to zero. So the next time someone tells you they dive in cold water but don’t get cold, you’ll know better. Just because they don’t feel it, doesn’t mean their body isn’t cold. They are either delaying the shivering point or they just don’t have enough bottom time.

Scuba diving is a beautiful and exciting sport. We need to be warm to maximize our enjoyment. There are sometimes rough seas, cold water, strong currents, bad visibility, gloomy weather and sometimes you get cold. There is not much we can do about the diving conditions, but you can always dive warm. The new technology is here and it is for everyone.

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