When you understand the effects of cold water on the body, and how the body responds, you are far more prepared to make life-saving decisions, either for yourself or in a rescue situation. The body loses about 2% of its heat through air conduction. However, water causes more heat loss from the body than air does, so heat can be lost from the body very quickly when it is placed in cold water. Convection (similar to sitting in front of a fan or having the wind blow on you). Mechanisms of Heat Loss or Transfer. Heat escapes (or transfers) from inside to outside (high temperature to low temperature) by three mechanisms (either individually or in combination) from a home or environment: Conduction. Convection. As in other mammals, thermoregulation in humans is an important aspect of homeostasis. In thermoregulation, body heat is generated mostly in the deep organs, especially the liver, brain, and heart, and in contraction of skeletal muscles.
In cold conditions Sweat production is decreased.
· The minute muscles under the surface of the skin called arrector pili muscles (attached to an individual hair follicle) contract (piloerection), lifting the hair follicle upright. This makes the hairs stand on end, which acts as an insulating layer, trapping heat. This is what also causes goose bumps since humans do not have very much hair and the contracted muscles can easily be seen. Osmoregulation is the active regulation of the osmotic pressure of an organism’s body fluids to maintain the homeostasis of the organism’s water content; that is, it maintains the fluid balance and the concentration of electrolytes (salts in solution) to keep the fluids from becoming too diluted or too concentrated.
· Arterioles carrying blood to superficial capillaries under the surface of the skin can shrink (constrict), thereby rerouting blood away from the skin and towards the warmer core of the body. This prevents blood from losing heat to the surroundings and also prevents the core temperature dropping further. This process is called vasoconstriction. It is impossible to prevent all heat loss from the blood, only to reduce it. In extremely cold conditions, excessive vasoconstriction leads to numbness and pale skin. Frostbite occurs only when water within the cells begins to freeze. This destroys the cell causing damage.
· Muscles can also receive messages from the thermoregulatory center of the brain (the hypothalamus) to cause shivering. This increases heat production as respiration is an exothermic reaction in muscle cells. Shivering is more effective than exercise at producing heat because the animal (includes humans) remains still. This means that less heat is lost to the environment through convection. There are two types of shivering: low-intensity and high-intensity. During low-intensity shivering, animals shiver constantly at a low level for months during cold conditions. During high-intensity shivering, animals shiver violently for a relatively short time. Both processes consume energy, however high-intensity shivering uses glucose as a fuel source and low-intensity tends to use fats. This is a primary reason why animals store up food in the winter. In addition to heat production by shivering, mitochondria can metabolize brown fat and produce heat energy via the thermogenin protein, in turn increasing the temperature of all cells in the body. Brown fat is specialized for this purpose, and is abundant in newborns and animals that hibernate.
Temperature is an indicator of the amount of heat contained in a system and in the human body our temperature is an extension of basic body metabolism and a host of other factors. Heat is a form of energy and every reaction in a human body occurs at a certain energy or temperature level thus tracking well with cell voltage and pH.
It is essential for the normal functioning of the human body, that this internal temperature be maintained, that pH be regulated and cell voltage optimized. The core body temperature of a human body is an important factor, which is always why it should be considered while evaluating the health condition in a checkup.
An important difference between mammals, including humans and other organisms like a reptile are that we are warm blooded creatures. The body temperature of mammals is maintained at a constant level, despite the changes in environmental temperature.
Hypothermia is a potentially dangerous drop in body temperature, usually caused by prolonged exposure to cold temperatures. The risk of cold exposure increases as the winter months arrive. But if you’re exposed to cold temperatures on a spring hike or capsized on a summer sail, you can also be at risk of hypothermia.
Normal body temperature averages 98.6 degrees. With hypothermia, core temperature drops below 95 degrees. In severe hypothermia, core body temperature can drop to 82 degrees or lower.
What Causes Hypothermia?
Possible causes of hypothermia include:
Cold exposure. When the balance between the body’s heat production and heat loss tips toward heat loss for a prolonged period, hypothermia can occur. Accidental hypothermia usually happens after cold temperature exposure without enough warm, dry clothing for protection. Mountain climbers on Mount Everest avoid hypothermia by wearing specialized, high-tech gear designed for that windy, icy environment.
However, much milder environments can also lead to hypothermia, depending on a person’s age, body mass, body fat, overall health, and length of time exposed to cold temperatures. A frail, older adult in a 60-degree house after a power outage can develop mild hypothermia overnight. Infants and babies sleeping in cold bedrooms are also at risk.
Normal core temperatures are at the exact temperature at which all the functions of the human body can operate with optimal efficiency. The same can be said about pH because all physiological processes are pH sensitive.
Normally the rectal temperature or vaginal temperature is considered as the core temperature. The ideal core temperature is considered to be around 98.6° Degree Fahrenheit or 37° degree Celsius. This temperature is however, the average body temperature and the overall normal temperature varies from a minimum of 97.7° Fahrenheit (36.5° Celsius) to a maximum of almost 99.5° Fahrenheit (37.5° Celsius). Any temperature above or below this range is abnormal. At the ideal temperature, all human body systems function with maximum efficiency with oxygen being supplied in ample amounts because CO2 levels are optimized.
Thermoregulation is the term for the body’s ability to maintain its core temperature (i.e., heart, lungs and brain) within specified boundaries. Normal core temperature ranges between 36.5° C and 37.5°C. This control is primarily provided by a portion of the brain called the hypothalamus which initiates a variety of responses to temperature fluctuations signaled by temperature receptors in the skin and core.
When the body is too warm, one cooling response is vasodilation which expands the blood vessels to increase blood flow to the periphery. This process may also be accompanied by sweating (another cooling response).
When the body is too cool, body heat is preserved: vasoconstriction narrows blood vessels to decrease blood flow to the extremities (hands/feet) and therefore decrease heat loss.
The brain may also initiate shivering thermogenesis to generate more heat. Shivering is an extremely effective means of creating body heat. At rest, we normally generate approximately 100 watts of heat. But when vigorous shivering occurs in the early stages of cold exposure and mild hypothermia, it can increase heat production up to 500 watts. Shivering is a good thing—it not only slows the onset of hypothermia but can also be an important aid in post-rescue rewarming.
When attempting to aid a potentially hypothermic victim, given the choice of drink, it would be better to offer a cold drink with sugar (to fuel shivering) than give them a warm drink that relies only on heat for rewarming (like warm water). The best possible option would be a warm chocolate drink that provides both heat and energy. Note: Be careful, however. Fluids should only be provided in cases of mild hypothermia where the victim is conscious, alert and won’t choke.
It’s actually quite simple: the body attempts to maintain a constant core temperature (Homeostasis) through a balance of heat loss and heat gain. Body heat is normally gained through activities such as exercise and shivering, and also with the application of external heat sources such as heat packs.
Body heat is lost in several ways, and there are four major mechanisms at work:
The heat generated from within the body is given-off to the surrounding atmosphere.
When you sweat or when your skin or clothing gets wet, the evaporation of that liquid (i.e., the change from liquid to vapour form) promotes heat loss, and the natural result is a cooling effect.
Convection is the process of air or water flowing by the skin and carrying away body heat. It’s convective heat loss that you try to prevent by staying as still as possible in the water. Staying still, the boundary layer of water next to the skin is heated by the body and remains undisturbed. If you move around in the water, you disrupt that boundary layer of warmer water, and that increases heat loss.
The body conducts heat to whatever the skin is in direct contact with. Conductive heat loss occurs when the skin is subjected to either cold air or water, but it is especially critical in water, as your body loses heat about 25 times faster in water than in air of the same temperature.
Once a body has been in cold water for an extended period of time, most of the skin is cool with little blood flow. However, there are critical areas that are lighter (warmer) than the surrounding tissue. This is because blood is flowing through major blood vessels, which are near the skin surface. These areas in the neck, armpits and groin are areas of high heat transfer. That means that these areas have high heat loss in the cold but allow heat gain in the heat. This is why, in a rescue scenario, the most effective rewarming often consists of applying external heat directly to the armpits as well as the chest.
Shivering is one of the most obvious and easily recognizable symptoms. Shivering is accompanied with chattering of teeth and goose bumps. Apart from this the following symptoms are observed:
· Slow heartbeat
· Shallow breathing
· Purple fingers and toes
· Lack of coordination
· Difficulty in making decisions
· Slurred speech
· Dilated pupils
· Weak pulse
One important factor that decides this temperature is the base metabolic rate of a body, which is the rate at which we burn calories and use up our energy stores. Other factors like administration of medications can also affect it, usually in a negative sense.
The control center for body temperature lies in the brain and it is known as the hypothalamus. The hypothalamus is alerted to either extreme cold or hot conditions reducing or opening blood flow towards the external layers of skin. Stress interferes with body temperature regulation driving down body temperature and its interesting the color green is warm and relates to the heart’s emotional center and the hypothalamus.
Changes in hand/foot temperature are a reflection of blood flow – a measure of the stress response. For example, while talking about an upsetting incident involving your parents, an employer/employee, or friend your temperature may drop 5_ to 20_. In contrast, when recalling a minor misunderstanding your temperature may only drop one degree. And yet, when you recall the warm sun on a recent vacation, your temperature may increase a full 10 %.
What is most surprising is how quickly the changes occur. People often comment, “I never had any idea that a little finger could show so much!”
The basic rule for interpreting temperature change is simple, Warmer hands/feet indicate Relaxation while Colder hands/feet reflect Activation or Tension. When the body’s fight/ flight system is activated the muscles tense, heart rate and the vital organs speed up. As a result, blood flow is shunted from the extremities and directed to the vital organs to facilitate the increased level of arousal. As a result, changes of 5, 10 or 15% can occur within just a few minutes.
Every process that goes on inside our bodies requires energy – specifically, metabolic energy. When the body does not have enough energy to function properly, each component of the body will malfunction in its own unique way. For example, if the brain has too little energy, thought processes such as memory and focus become impaired. The body needs energy to keep itself warm – a low body temperature, therefore, usually accompanies low metabolic energy.
As a final note, it’s important to realize that the activity of swimming (which is naturally thought of as producing a heat GAIN), in cold water conditions will result in increasing the blood flow to blood vessels close to the skin, and because of Conduction and Convection, can actually increase the rate of heat LOSS and expedite the onset of hypothermia.