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 intra¬
luminal 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
