Skin temperature

Subcutaneous injection of 100—750 mg/kg sulfolane at an ambient temperature of 10°C also caused a dose-dependent decrease in colonic temperature of rabbits. MetaboHc rate remained unchanged during the initial phase of the hypothermia for all dose groups but peripheral vasodilatation, as indicated by an increase in ear skin temperature, was seen at the higher dose levels (29). 

Skin. The skin may become contaminated accidentally or, in some cases, materials may be deHberately appHed. Skin is a principal route of exposure in the industrial environment. Local effects that are produced include acute or chronic inflammation, allergic reactions, and neoplasia. The skin may also act as a significant route for the absorption of systemicaHy toxic materials. Eactors influencing the amount of material absorbed include the site of contamination, integrity of the skin, temperature, formulation of the material, and physicochemical characteristics, including charge, molecular weight, and hydrophilic and lipophilic characteristics. Determinants of percutaneous absorption and toxicity have been reviewed (32—35,42,43,46—49). 

The skin receives heat from the core by passive conduction and active skin blood flow (Table 5.3). It transfers this heat to the surroundings by convection, radiation, and evaporative (perspiration and diffusion) mechanisms. All of these mechanisms are unregulated or passive except evaporation from sweating. The sweating process is actively controlled by the humarrs thermoregulatory center where the rate of sweat secretion is proportional to eleva tions in core and skin temperature from respective set point temperatures (Table 5.3). 

When the energy flows in and out of a compartment do not balance, the energy difference accumulates and the temperature increases or decreases. The changes in core and skin temperature then in turn alter the physiological control signals to restore balance and thermal stability. 

The consequence of the relationships of Table 5.3 and Fig. 5.2 is that for a neutral thermal sensation, at steady state, the core temperature increases while the skin temperature decreases with increased metabolic activity (Fig. 5.3). The increase in metabolism causes sweating which decreases skin tem-perature. 

The thermal parameters for comfort should be relatively uniform both spatially and temporally. Variations in heat flow from the body make the physiological temperature regulation more difficult. Nonuniform thermal conditions can lead to nonuniform skin temperatures. The active elements of the regulatory system may need to make more adjustments and work harder in order to keep thermal skin and body temperatures stable. To avoid discomfort from environmental nonuniformities, the temperature difference between feet and head should be less than about 3 °C (Fig. 5.9) and the mean surface temperature or radiant difference from one side of the body to the other should not he greater then about 10 °C. 

Local air motion is another thermal nonuniformity that can cause a local cooling of the skin and the feeling of a draft. Draft discomfort from local air motion increases as the air temperature decreases below skin temperature. Fluctuations in the local air motion increase the perception of drafts and should be avoided. The unsteadiness of air motion is often described in terms of its turbulence intensity (Tu) ... 

ISO EN 9886 presents the principles, methods, and interpretation of measurements of relevant human physiological responses to hot, moderate, and cold environments. The standard can be used independently or to complement other standards. Four physiological measures are considered body core temperature, skin temperature, heart rate, and body mass loss. Comments are also provided on the technical requirements, relevance, convenience, annoyance to the subject, and cost of each of the physiological measurements. The use of ISO 9886 is mainly for extreme cases, where individuals are exposed to severe environments, or in laboratory investigations into the influence of the thermal environment on humans. 

Mean skin temperature The average temperature of the skin exposed to a given environment. 

The dewpoint for the flue products from gas is a maximum of 60°C and will, in most cases, be lower because of excess air. There is no acid dewpoint because the sulfur content is negligible. It would be thought that condensation would be most unlikely, and this is so for the bulk flue gases. However, the temperature gradient across the flue wall can be such that the skin temperature at the inside wall can be considerably less than the bulk temperature, and condensation will take place. 

The main corrosion processes that occur in these items arise from condensing liquids on the internal surface. Although often lagged, heat loss frequently causes internal skin temperatures to fall below the dewpoint of one or more components of the gas stream, albeit locally, such as at support points. Even at temperatures above its dewpoint a gas can dissolve in condensed water. Rapid corrosion can then occur in this thin film of corrosive liquid. 

It has been concluded from data reported in these studies that the skin temperature is the major controlling factor in corrosion, not the rate of heat flow through the metal . It has also been concluded, however, that corrosion rates at a given mid-specimen temperature do depend on the presence or absence of thermal flux . The difference between temperatures at skin and mid-specimen positions may account for this discrepancy. 

Solar radiation may fall on outside walls or roofs, raising the skin temperature, and this must he taken into account. Most cold stores are huilt within an outer envelope which protects them from the elements and from direct sunshine. In cases where the insulation itself is subject to solar radiation, an allowance of 5 K higher outside temperature should he taken. Heat load must he estimated through all surfaces including piping, ducts, fan casings, tank walls, etc., where heat flows inwards towards the cooled system. 

Insufficient water leads to locally elevated metal skin temperatures ... 

Short-term overheating may take place when the metal temperature exceeds 850 to 900 °F (454-482 °C). Where dry firing occurs, the skin temperature may quickly rise to 1,200 to 1,500 °F (684-815 °C) or higher. 

If the patient has a DVT, it usually occurs in a lower extremity. The nurse examines the extremity for color and skin temperature The nurse also checks for a pedal pulse, noting the rate and strength of the pulse. It is important to record any difference between the affected extremity and the unaffected extremity. The nurse notes areas of redness or tenderness and asks the patient to describe current symptoms. The affected extremity may appear edematous and exhibit a positive Homans sign (pain in the calf when the foot is dorsiflexed). A positive Homans sign is suggestive of DVT. 

The nurse examines die skin temperature and color in die patient with a DVT for signs of improvement. The nurse takes and records vital signs every 4 hours or more frequently, if needed. 

External conditions can also cause a decrease in arousal that may also affect cognitive/psychomotor performance. An interesting stimulation study conducted by Suedfield and Eich136 showed how arousal can be reduced. They used Restricted Environmental Stimulation Technique (REST), in which a subject floats in a dense solution of skin temperature water and Epsom salts. This technique was shown to decrease subjective reports of arousal. Similar reports come from studies of meditation137-138 and systematic relaxation.139... 

In addition, the use of biological monitoring has the advantage that skin penetration under particular conditions of protective clothing is included as well in the approach. The results of a dose-excretion study of propoxur by Meuling et al. (1991) using volunteers indicate a significant increase of the dermal uptake of the compound under conditions of occlusion, where there is increased blood flow, skin temperature, and skin moisture. 

---