Cryoglobulinemia and the cold.
Avoiding body heat loss is a vital tactic in living with Cryo as cold exposure triggers Cryo flares. The body loses heat in 4 ways….Conduction, Convection, Evaporation and Radiation.
Because, by definition a draught is slow moving, it has maximum opportunity to wick heat away from exposed skin. The more exposed skin available and the greater the temperature difference between air and skin, the more dangerous the situation. Duration of exposure would also be a factor.
Fabrics and Your Body
Cotton “flashes off” (dries out) very quickly. More woolen fabrics have much longer flash off times. As it is body heat driving the evaporation a wet cotton fabric will use your heat shockingly rapidly. A woolen fabric retains moisture much longer, losing your body heat more gently. It may be that a sweat heavy wooly jumper layer might be the best option in some circumstances. It also looks like swimming is off the agenda. Along with breathing too deeply of cold air.
Conduction
Conduction is the loss of heat through direct contact with a cooler object. Heat loss is greatest if the body is in direct contact with cold water. The body can lose 25 to 30 times more heat when in contact with cold wet objects than in dry conditions or with dry clothing. Generally, conductive heat loss accounts for only about 2% of overall loss. However, with wet clothes the loss is increased 5 times.
Convection
Convection is the loss of heat from the body to the surrounding air as the air moves across the surface of the body. The rate of heat loss from the skin by contact with cold air depends on the air speed and the temperature difference between the skin and the surrounding air. At a given air temperature, heat loss increases with wind speed. However, the effect of wind speed does not increase at speeds above 64 km/h or 50 mph since the air is not in contact with the body long enough for more body heat to be transferred to the air.
Evaporation
Evaporation is the loss of heat due to the conversion of water from a liquid to a gas. In terms of human physiology, it is:
Perspiration/Sweating – evaporation of water to remove excess heat.
“Insensible” Perspiration – body sweats to maintain humidity level of 70% next to skin. Particularly in a cold, dry environment, you can lose a great deal of moisture this way and not notice that you have been sweating.
Respiration – air is heated as it enters the lungs and is exhaled with an extremely high moisture content.
It is important to recognize the strong connection between fluid levels, fluid loss, and heat loss. As body moisture is lost through the various processes, the overall circulating volume is reduced which can lead to dehydration. This decrease in fluid level makes the body more susceptible to hypothermia and other cold injuries.
Radiation
Radiation is the loss of heat to the environment due to the temperature gradient. In this case, it is the difference between the temperature of the air and the temperature of the body (your body’s core temperature is +37°C). Another factor important in radiant heat loss is the size of the surface area exposed to cold.
