Hyperthermia and Scuba Diving: How to Prevent Overheating


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overheating while diving

Thermal challenges, especially excessive heat loss and hypothermia, are fairly common among divers. After all, water is usually cold in relation to the human body and has a higher thermal conductive capacity than air, so our bodies lose heat faster. This doesn’t mean, however, that the other side of the coin, hyperthermia, is never seen. So, today we will look at how to prevent, recognize and deal with overheating while scuba diving.

What Is Hyperthermia

The word hyperthermia comes from Greek, where hyper means “over” or “above” and therme means “heat”. So hyperthermia is when the body’s core temperature rises above its normal, healthy level. The condition occurs when the body's heat-regulation system becomes overwhelmed by outside factors and is considered separate from issues where internal body sources, such as infection or heat-regulating problems, cause a raised body temperature.

There are a few different phases of hypothermia - heat edema, heat cramps, heat syncope, heat exhaustion, and heat stroke. The lower limit of hyperthermia is poorly defined, while its most severe form - heat stroke occurs when someone's core temperature exceeds 104°F (40°C).

It is worth noting that how an individual’s core temperature responds to heat is strongly influenced by their state of acclimatization (the adaptation to repeated or sustained high temperatures), the arduousness of any physical work they're doing, and the relative humidity of the environment.

Hyperthermia and Diving

When the ambient temperature is too high, the body relies on sweating and, more importantly, the evaporation of sweat to shed excess heat. Although immersion in water prevents evaporative cooling, temperatures high enough to cause discomfort (above 97°F (36°C)) are not typically experienced by recreational scuba divers.

More common stressors are exposure to hot surface conditions, particularly when divers are wearing insulated suits (especially drysuits), and perform strenuous physical work, such as carrying dive equipment on land. Wetsuits and drysuits, in addition to being predominantly black, allow little-to-no airflow against the skin. This inhibits evaporative cooling and causes the body to warm up very quickly. The problem is further exacerbated by warm temperatures and sunny conditions, typical of a lot of dive destinations. Due to this, most hyperthermia cases with scuba divers happen while on the boat or shore and often because of overheating while wearing a wetsuit and waiting to get in the water.

Preventing Hyperthermia

Luckily, hyperthermia can be easily avoided of you follow a few simple rules.

1. Keep hydrated. As it was mentioned before, sweating and having that sweat evaporate on the skin, helps the body to cool itself. In order for this mechanism to continue to work properly, you need to maintain an adequate body fluid volume, which simply means drinking enough. Cool fluids (water or drinks containing electrolytes) help to regulate the body’s temperature and should be consumed frequently. Alcohol and caffeinated beverages are not recommended as these fluids generally increase the risk of dehydration. Hot meals can also heat up the body’s core temperature and should be avoided during particularly hot conditions.

2. Allow your skin to breathe. Wait until the last minute to change into your exposure suit. Wear it only after you’ve put all your gear together and are otherwise ready for the dive. If you’re in your exposure suit and, for some reason, there’s a delay in getting to the water, pour some water over yourself, and inside your suit, to cool off a bit.

3. Stay in the shade. With or without an exposure suit on, try and get out of the sun. Find a shaded, cooler, air-conditioned or well-ventilated area that is not crowded and provides a break from extreme heat.

Signs and Symptoms of Hyperthermia

The signs and symptoms of hyperthermia vary, according to how severe the condition is. A person experiencing hyperthermia may have all or some of the following phases and symptom developments:

Heat edema (swelling) - the accumulation of excess fluid in the body's tissues and cavities. This condition often manifests itself as swelling in the lower legs, ankles, and hands.

Heat cramps - involuntary muscle spasms and aches (usually in the arms, legs, and abdomen) due to the lack of salt in the muscles. Sweating, caused by heat in combination with exercise, effectively depletes salt and moisture levels, leading to electrolyte imbalance, which, in turn results in heat cramps.

Heat syncope - fainting, or a temporary loss of consciousness. When to effectively treated, heat fatigue, cramps, and edema can progress to a state of feeling faint. When this occurs, the body experiences a drop in blood pressure, which results in a lack of sufficient blood flow to the brain. This temporary lack of blood flow can lead to what is known as the heat syncope phase. Other signs which precede a syncopal episode may include:

  • Nausea and or / vomiting;
  • Weak pulse;
  • Slurred speech;
  • Sudden sweating (clamminess – cool and moist skin);
  • Pale complexion;
  • Headache;
  • Vision disturbances (seeing spots, blurry vision, tunnel vision, and dilated pupils);
  • Hearing disturbances (sounds may feel like they are suddenly very far away);
  • Vertigo (sensation of spinning);
  • Body weakness;
  • Shaking.

Heat exhaustion - a condition when the body is almost entirely unable to cool to a normal temperature naturally due to an excessive amount of water and salt lost through perspiration. Similarly to heat syncope, heat exhaustion is characterized by headache, nausea or vomiting, low blood pressure, dizziness, fatigue and temporary loss of consciousness. The victim’s rectal temperature may raise to 104°F (40°C). If left untreated, this condition can fairly quickly progress to heat stroke.

Heat stroke - the most severe phase of hyperthermia that is considered a medical emergency. Once internal body temperature is in excess of 40°C (104°F) and rising rapidly, a person is considered to have reached the stage of heatstroke. At this temperature, the brain and other crucial internal organs are at risk of serious damage or total failure. The severity of the damage depends on the length of time a person has been exposed to intense heat. Heat stroke is characterized by a pronounced change in mental status, severe headache, nausea or vomiting, loss of consciousness and often cessation of sweating.

Dealing With Hyperthermia

A person should immediately stop what they are doing and move to a cool, shaded place with good airflow if they suspect hyperthermia. The greater the magnitude of the malady, the more aggressive the efforts to cool the victim must be.

Heat edema is easily resolved with rest and elevation of the extremities.

Heat cramps can be managed with ice massage (rubbing an ice cube on the affected area for five minutes at a time), stretching, and drinking fluids to rehydrate the body. People should seek medical attention if heat cramps last longer than one hour after they have rested in a cool place.

Additional tips for treating mild to moderate hyperthermia include:

  • sipping cool water or an electrolyte drink;
  • loosening or removing excess clothing;
  • lying down and trying to relax;
  • taking a cool bath or shower;
  • placing a cool, wet cloth on the forehead;
  • running the wrists under cool water for 60 seconds;
  • not resuming activity until symptoms have gone away.

Heat syncope and heat exhaustion require monitoring the victim’s vital signs and core temperature, administering electrolyte-rich fluids, and ensuring rest and cooling. If the victim's signs or symptoms worsen or if they don't improve within 15 minutes, seek emergency medical help.

If you suspect that someone has a heat stroke, immediately call an ambulance as any delay in seeking medical help can be fatal. While waiting for the paramedics to arrive, initiate first aid. Move the person to a cool, shady area and remove any unnecessary clothing. Fan air over the victim while wetting their skin with water from a sponge or garden hose. Apply ice packs to the victim’s armpits, groin, neck, and back. Immerse the victim in a shower or tub of cool water.

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