The use of infrared radiation to reduce heat loss in burned patients: experiments with a phantom

Can Wound Desiccation Be Averted During Cardiac Surgery? An Experimental Study

During cardiac surgery the wound is exposed to desiccation, especially as a result of operating room ventilation and the insufflation of dry carbon dioxide (CO(2)) for de-airing. We compared the gas humidity and desiccation rates in an in vitro model of a cardiothoracic wound during these conditions and during insufflation of humidified CO(2). To assess the influence of flow velocity, CO(2) was insufflated at 10 L/min via two devices, a standard open-ended tube and a low-velocity gas diffuser. The treatment arms were compared with a control without insufflation. When insufflated via the open-ended tube the humidity in the model was almost equal to the control, both with dry and humidified CO(2). However, the total desiccation rate was more rapid than the control (P < 0.001), especially in the area exposed to the gas jet where the desiccation rate was three times more rapid (P < 0.001). With the gas diffuser, dry CO(2) caused almost zero humidity and a desiccation rate that was almost equal to the control. Humidified CO(2) increased humidity in comparison with the control (P < 0.001) and decreased the desiccation rate by >90% (P < 0.001). Humidified CO(2) may be used to avert desiccation of the cardiothoracic wound. The humidified gas is effective only when delivered via a low-velocity outlet device.

Exposure treatment of the burned patient--a computer simulation of the thermal environment and its effect on evaporation and heat loss

The influence of the thermal environment on evaporation and heat loss from burned tissue has been studied in order to optimise conditions for treatment of severely burned patients. Diffusion resistances have been defined to describe movement of water vapour through the skin and away from the body surface. These have been evaluated from experiments on a water phantom and from data on evaporation rates from burned tissue and normal skin. Results show that the diffusion resistance for burned tissue is less than one tenth of that for normal skin, but changes substantially during the development of an eschar. Evaporation is promoted by a high skin temperature and a low relative humidity, but not by raising the ambient air temperature. Blowing warm dry air over a burn wound will enhance evaporation and reduce heat loss, encouraging the rapid formation of a dry eschar to provide a barrier against infection. Selective irradiation of burned tissue with low levels of radiant energy can be used to compensate for local heat losses, and allow the air temperature in the treatment room to be kept at a level comfortable for the patient and nursing staff.

The influence of environmental factors on evaporation and heat loss from burned tissue

Destruction of skin by severe burning leads to substantial loss of fluid. Increased evaporative heat loss in addition to energy demands for tissue repair causes hypermetabolism in a severely burned patient, placing a large stress on the body. The dependence of evaporation rate and energy supply on environmental variables has been studied using a phantom in which a free water surface simulated burned tissue. Vapour diffusion resistances have been derived from the experiments, and compared with values calculated from data obtained from other studies of burned tissue. These can be used to predict rates of evaporation and heat loss for burned tissue, and their dependence on different environmental factors. Experiments have shown that energy in the form of radiant heat or warm air blown over the water surface can be supplied to reduce heat losses without significantly affecting evaporation rate.