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Title: The design, construction and application of apparatus for telemetering biological data from the human alimentary tract
Author: Ridgway, Malcolm G.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1962
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A considerable period at the beginning of this work was devoted to the design and construction of the miniaturised electronic and mechanical units required for the capsule part of the telemetering system. The initial difficulties with small components and the micro-manipulation techniques had been almost overcome and the prototype 'probes' were nearing a final state when it was discovered that a similar unit was soon to become available commercially. It did not seem worthwhile continuing work on the capsule at that time, but since I was able to anticipate the appearance of the commercial version, by the time that it appeared on the market, in October 1960, I had built an external detecting system so as to be able to estimate the effects of attenuation through the abdominal wall and movement of the capsule within the bowel; factors which at that time were unknown. As a result of these experiments the original receiving unit was modified and in March 1961, a series of clinical trials was started,in conjunction with a medical colleague, to establish the possible uses of the capsule telemetering method. The instrument, which was developed for measuring pressures within the bowel using a mobile, rather than stationary, transducing system proved quite adequate both for assessing the immediate applications of the system and for estimating its potential for more comprehensive studies. Further refinements, such as a non-directional aerial array, which would have made the routine studies more convenient and a more elaborate receiver with better longterm stability which would have increased the accuracy of the system during extended experiments were put aside in favour of the clinical experiments. This uncertainty in the basal levels was not a serious limitation, however, because we did not attempt to make the complicated computations, involving variations in abdominal pressures and the hydrostatic effects of viscera overlying the bowel, which would have been necessary to deduce absolute pressure levels within the bowel. We devised a method for localising the capsule, using contrast techniques and a series of two or three abdominal radiographs to enable us to make estimates of the long-term movements of the capsule. A method of monitoring the changes in signal intensity was also adopted to enable us to form some idea of the short-term movements of the capsule, as well as making a record of the intra-luminal pressure variations. Neither the method for localising the capsule, nor the monitoring of the short-term movements was sufficiently accurate to make really precise studies, but they allowed us to start the clinical experiments without further delay. The capsule technique proved to be extremely successful in that the clinical procedures involved were simple and from the patient's point of view, completely a traumatic. The uncertain length of the gastric phase presented a practical difficulty which we were not able to solve satisfactorily and sometimes an interesting part of the experiment was missed on this account. The length of the transit periods through the intestine appeared reasonable compared to known rates of transport, although the inertia of the capsule prevented a direct comparison with the more realistic estimates using fluid markers. We were, therefore, satisfied that the capsule did not lead to direct stimulation of the bowel as previous intubation methods have been thought to do, although as 1 have explained earlier, the nature of the method is such that we could not prove this by a direct experimental comparison. The periods of complete quiescence which were recorded on many occasions from all levels of the major organs were also inconsistent with local stimulation. We carried out 40 clinical experiments, each of which involved, on average, 2 or 3 days of recording. The investigations included series of normal controls, a number of patients with abnormal functional conditions and a short series of post-operational studies. The large amount of data collected from each of these experiments was found to be something of a problem because the salient features were sometimes obscure and the records required a careful evaluation which we did not succeed in reducing to a concise, quantitative form. Because of this difficulty, the method did not yield as much information on bowel motility as we had anticipated that it would. The most successful application was found to be the 'all or none' type of experiment, such as the post-operational studies, where we were primarily concerned with showing only that pressure activity was present within a certain period of time and certain of the tests on patients with functional disorders where we were able to show that the affected parts of the bowel still had some muscular ability. The mobility of the capsule sometimes led to uncertainty about the exact site at which it was lying, which was particularly troublesome at times when unusual phenomena were recorded. This uncertainty, which made it virtually impossible to extract meaningful information from motility studies in the stomach could only be removed by tracking the capsule as it moved through the alimentary tract. The simple, qualitative method we adopted to study the short-term movements of the capsule suggested very strongly that a much more comprehensive study of motility could be made if we utilised the mobility of a small capsule with low-inertia to make quantitative recordings of transport along the bowel, as well as the complementary study of intraluminal pressure. It does not seem practicable to reduce the present form of the capsule, but a different approach using an externally energised 'probe' may provide the solution. Also the problems of interpreting the data might be t simplified if a different type of measurement could be made which excludes variations from extra-luminal pressure fluctuations. A lighter capsule of about the same length as the present 'probe* with a differential pressure transducing system which transmitted a measure of relative changes between the ends of the capsule might prove to be a more potent instrument for examining motility, particularly in the small bowel. A differential measurement would also exclude the extra-luminal effects. A few difficulties, therefore, remain to be solved before telemetering from within the human body can become a routine clinical procedure, and in conclusion I would like to express the hope that these studies will form a useful basis for the practical advancement of these 'tubeless' techniques.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available