Pneumatic tourniquets are widely used in surgery of the extremities to occlude the vessels of the limb, thereby providing a bloodless field for dissection so that the surgeon may operate more quickly and accurately. Over-pressurization of the tourniquet cuff may lead to postoperative complications such as temporary or permanent paralysis of the limb. This motivated the development of adaptive tourniquet systems which could regulate the tourniquet pressure just above the limb occlusion pressure (LOP), or the minimum tourniquet pressure required to prevent blood flow past the cuff for a given duration. Previous adaptive tourniquet systems suffered from several problems which limited their practical utility in the operating room. This thesis describes the adaptation of oscillometry, a technique widely used in the noninvasive estimation of blood pressure, to the estimation of LOP in the surgical environment for application in a clinically practical adaptive tourniquet system. Improved oscillometric LOP estimation performance was obtained through the development of a filter for increasing the signal-to-noise ratio of the oscillometric pulses during periods of limb manipulation, the development of a heuristic real-time pattern recognition algorithm for extracting oscillometric pulses from signal data corrupted by limb movements, and the development of a new method for rapidly estimating the LOP which needs only one-third of the signal data required by a widely-used oscillometric approach to produce an estimate of comparable accuracy. In addition to these contributions, a new tourniquet cuff was developed which achieves an improved fit to the limb, thereby enhancing performance and reliability over that obtained from conventional tourniquets as both an oscillometric occlusion sensor and as a limb-occluding device. An adaptive tourniquet system which integrated these improvements was developed and used in a clinical study involving four orthopaedic surgeons and 16 patients. Clinical trials of the latest system version in which circumstances permitted the use of adaptive control showed that the average limb-applied pressure was reduced by 35%, or from the conventional standard of 250 mm Hg to 162 mm Hg, in the upper limb surgeries, and by 38%, or from the conventional standard of 300 mm Hg to 187 mm Hg, in the lower limb surgeries. These significant reductions in the pressure indicate the potential effectiveness of adaptive tourniquet control and improved cuff design on reducing the risk of patient injuries from excessive tissue compression. Furthermore, unlike all previous implementations, this system is currently being evaluated on a routine basis in orthopaedic surgical procedures performed at Vancouver General Hospital. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The object of this research project is to investigate the base catalyzed reaction of acetic anhydride and isobutyl alcohol reacting to form acetic acid and isobutyl acetate. In this investigation, a high frequency oscillometer is used to observe the progress of the reaction as it proceeds to the formation of products. The chemical oscillometer, in one form or another, has been in existence for over twenty years. During this time it has developed from a laboratory curiosity to a practical instrument with a great number of applications. However, its use in connection with kinetic studies has not been too active because of the fact that it has been used primarily as a purely analytical device. A more detailed description of the instrument as well as a brief background of its use will be presented in the following chapter. Another purpose of this investigation is to determine how the velocity of the reaction in question is dependent upon the temperature of the vessel or environment in which the reaction is taking place. In other words, several rate determinations will be made at various temperatures in order to establish the relationship between these two variables. From the data obtained from this series of rate determinations, it becomes possible to calculate a theoretical term known as the energy of activation, the significance of which will be explained in Chapter IV.

It is the purpose of this investigation to determine the feasibility of using a 120 megacycle oscillometer for kinetic studies in non-aqueous solutions by studying the reaction rate of the base catalyzed esterification of acetic anhydride.