The relationship between the human body and the dissemination of potentially pathogenic particles and droplets is described. Airborne transmission of infection in operating theatres and a burns unit and the part played by the human microclimate and its interaction with ventilating air flows is discussed. The mechanisms by which different garment assemblies used for surgery can enhance particle dispersion are illustrated and the way that floor cleaning can increase the concentration of airborne organisms is described. The development of the successful use of ultra-clean air systems in orthopaedic implant surgery is reviewed. Relationships between contact and airborne transmission of disease are explored and ways by which containment strategies and metrics used in pharmaceutical and electronics manufacturing can be applied to the design and monitoring of healthcare areas is discussed. It is suggested that currently available techniques involving architectural, ventilation and operational aspects of healthcare provision, when properly applied, can markedly improve treatment outcomes that may otherwise be compromised by hospital-acquired infections involving both bacteria and viruses.

SUMMARYInfra-red colour thermography has been used to visualize skin temperatures in two athletes standing and running in an outdoor environment at 200 C and in a climatic chamber at 110 C. Temperature distributions and changes have been recorded on film and analysed. Mean skin temperatures determined by this method have been compared with skin temperatures obtained with a probe thermocouple.During running, skin temperatures were higher over muscles than over other structures and the distribution differed dramatically from that observed before exercise.Regional mean skin temperatures obtained by thermography differed by up to 40 C from those obtained with the thermocouple probe. Overall mean skin temperatures obtained by both methods agreed to within 1.50 C.

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1. Infra-red Colour Thermography was used to visualize skin temperatures over seven neonates nursed in a modified temperature controlled incubator. 2. Temperature distributions were recorded on cine film which was analysed to evaluate mean skin temperatures; these were subsequently compared with values obtained from multiple, weighted measurements from a thermocouple thermometer. In all cases, there was agreement to within +/- 0 . 6 degrees C. 3. Thermograms in thermo-neutral conditions (approximately 32 degrees C) showed a temperature distribution with the warmest skin overlying the central hot 'core' and temperatures falling towards the extremities. Temperature patterns in a cooler environment (approximately 28 degrees C) showed features due to the conductive or thermogenic nature of the structures underlying the skin. 4. Multiple skin temperature recordings made at two environmental temperatures were obtained from a further twelve infants. 5. Linear regression of skin temperature against rectal--environmental difference, performed for each of the measured sites, showed that the upper arm and, to a lesser extent, the upper thigh temperatures represented the mean value most closely. The upper abdomen and head were both warmer and less responsive to environmental change than the mean skin temperature. These findings were supported by the thermographic observations.

The formation of pressure ulcers can be exacerbated by a breakdown in the integrity of the patient's skin caused by poor maintenance of the skin microclimate. Patient support systems (PSSs-specialised beds, mattresses, chairs, cushions and pads) play an important role in the dissipation of heat and moisture away from the skin/support interface which is necessary in order to maintain the physiological skin microclimate. This paper reports a laboratory method and theory for the simultaneous measurement of the heat and water vapour dissipating properties of PSSs. The results demonstrate that the method is extremely selective, exhibiting very significant differences between the PSSs tested. It also shows that assessing PSS covers independently does not necessarily indicate the overall performance of the complete PSS.