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Wheelchair sitters with insensitive skin have a high risk of developing pressure sores. Prolonged pressure produces ischaemic conditions in the underlying tissues which may lead to cellular death and necrosis. Properly designed seating may reduce this risk and prevent the onset of pressure sores. To achieve the best protection possible a method of objective evaluation is required which will account for variations in tissue quality, sitting behaviour and sitting biomechanics. This thesis reports on the application of thermography into a tissue trauma seating programme and the quantification of isotherm areas for statistical comparisons of skin temperature response to experimental parameters. The thermographic research is presented in three phases of analysis: Chapter 4, a retrospective study of thermograms based on maximum temperatures; Chapter 5 both maximum temperatures from the real-time thermograph display and automatically collected areameter isotherm area data; and Chapter 6, a prospective patient study based on isotherm area data. During the preliminary stages of research, patients were followed with thermographic examinations at various stages of fitting and trial sitting on wheelchair cushions. There followed a series of tests with able-bodied subjects on experimental seats in an environmental chamber to determine the minimum conditions required for quantitative measurement of thermographic data. The examination room at the Ontario Crippled Children's Centre was then modified accordingly for patient studies and quantitative techniques were tested further. The results of these three phases of reseach are presented with recommendations for continuing studies. The acquired information supports the use of thermography in tissue trauma programmes. Sites of accumulated stress were found to be identifiable and approaches tor the quantitative comparison of thermal response to sate and unsafe loading conditions presented. Maximum temperatures were the most sensitive measures of hyperthermic response and mean imaged temperatures, the most readily characterized for cooling. Detailed discrimination of differences in skin cooling were found to be enhanced when the area of examination was minimized.

Changes in heart rate; oral temperature; mean skin temperature; urinary pH, volume, sodium, potassium, chloride, urea and creatinine; salivary pH, sodium, potassium and urea; expired air and oxygen consumption have been monitored in young men doing ( 1) exercise on an ergometer for 4 min at 10C, 20C, 30C and 40C dry bulb 50% rh at 120-320 W; (2) 20 min at 30C dry bulb at 50% rh, 60% rh, and 85% rh at 120W, 145W and 170W; and (3) 60 min at 20C, 30C and 40C dry bulb and 50% rh at 170w. Changes in work rate, environmental temperature, relative humidity and exposure time were found to correlate well with the urinary and salivary changes and in most cases changes in both work rate and ambient temperature produced simple summation effects. The increase in salivary components correlated well with the decrease in urinary components. Salivary sodium, potassium and Na+/K+ ratio increased significantly when work intensity, exposure time and environmental temperature were increased. Salivary urea correlates significantly with increased exposure time. The elevated values for salivary components may be explained on the basis of volatilization caused by forced ventilation during exercise; increased penetration of plasma components into saliva; increased water reabsorption, decreased sodium reabsorption, and increased potassium secretion in the ductile system of the salivary glands due to increased sympathetic activity. The results show that changes in saliva give a valid indication of the body's response to work and environmental stress and suggest that saliva could be used to study the combined effects of work and heat in places where it is impracticable to obtain samples of blood or urine.