Instrument design, application and investigational analysis of the external factors, pressure, humidity, and temperature in the pathogenesis of decubitus ulcers

Trandel, Richard Samuel, Mechanical Engineering, University of Virginia
Trandel, Richard S., School of Engineering and Applied Science, University of Virginia
Lewis, David W., Physics, University of Virginia
Gibson, John E., School of Engineering and Applied Science, University of Virginia

Ever since the conceptual introduction of externally applied tissue pressure as a causative factor in the generation of tissual necrosis, researchers have made great contributions in defining pressure as a primary factor causing decubitus ulcers.
In the past half century many investigators such as Brooks and Duncan, Husain, Kosiak, and Lindan, all working with animals, have definitely proven that a time-pressure relationship for the formation of decubitus ulcers does exist. The greater the pressure applied to the tissue, expecially over bony prominences such as the occiput, the scapula, the sacrum, greater trochanter, and the calcaneum, the shorter the time necessary to produce necrosis of the affected tissue.
In the last two decades Schell, Reichel, Lowthian, Baker, Wildnauer, Sacha, and others have shown that the causation of decubitus ulcers is not only related to
external pressure but also to factors such as local skin temperature, relative humidity, shear stresses, and friction forces.
The intent or this dissertation is to concern itself with conceptual design, fabrication, implementation, and evaluation or instrumentation and apparatus needed to clinically measure body pressure, relative humidity, and skin temperature that exists between the patient and his supporting surface.
Specifically, two pressure transducers and a humidity sensor have been designed and fabricated. Both are small in size, soft and pliable, easily used and read, and relatively inexpensive. A portable pressure calibration chamber and a portable pressure measuring system have been developed to adjuvant the pressure transducer. A unique patient lift bed with a transparent supporting surface has been created for making visual and photographic observations, thermographic infrared radiation, pressure and humidity measurements of the integument during body loading.
An investigational and statistical analysis has been conducted upon the sacrum of 21 healthy male and female subjects. The experiment basically consisted of measuring the maximum sacral pressure, relative humidity, and skin and body temperature subjected to body load. Thermograms indicating the reactive hyperemic response were taken with respect to time after relinquishment of body load.
The pressure transducers, relative humidity sensor, supporting equipment, lift bed, and experimental data (statistical and thermographical) are discussed, evaluated, and conclusions presented.

PHD (Doctor of Philosophy)
Pressure--Measurement, Bedsores

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