Measuring and testing – Muscular force
Reexamination Certificate
1995-03-13
2002-04-23
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Muscular force
Reexamination Certificate
active
06374670
ABSTRACT:
TECHNICAL FIELD
This application relates to a non-invasive apparatus for and method of monitoring gut motility. In particular, it relates to such an apparatus and method which utilizes a swallowed magnet which can be monitored externally by an electronic flux-gate compass. Gut motility is indicated by linear and rotational movement of the magnet measured by the external compass.
BACKGROUND OF THE INVENTION
The gut is a hollow organ that extracts nutrients and water from food as it is transported from the mouth to the rectum. The muscles of the gut are arranged as longitudinal and circumferential layers. They contract under mechanical, autonomic and humoral control so as to transport and mix their contents by moving them alternately in a forward and reverse direction. This transport and mixing is generally termed “gut motility.”
Over 22,000,000 patients in the United States have presented physicians with unexplained bowel symptoms, such as constipation, diarrhea or abdominal pain. Chronic gastrointestinal disorders may result from conditions brought on by diabetes or a variety of symptoms generally labeled as “irritable bowel syndrome” (IBS). Patients suffering from IBS are given a series of gastroenterological and radiological tests to diagnose disease and assess gut function. Because the presently-available diagnostics are relatively expensive and uncomfortable, patients usually go through a barrage of tests to rule out other known diseases or disorders prior to undergoing tests that heretofore were best for assessing abnormal gut motility.
The most commonly-used diagnostic tool, orogastric manometry, is usually used only after other less invasive and less costly procedures have been exhausted due to the high cost and patient discomfort/intolerance associated with orogastric manometry. Orogastric manometry has previously provided the most quantitative assessment of upper gastrointestinal muscular function and disorder but can provide information about the action of only the esophagus, stomach, duodenum and perhaps the first six inches of the proximal bowel, known as the duodenojejunal flexure.
Anal manometry provides information about the descending colon, sigmoid colon and rectum. Neither manometry technique provides data about the condition of the ileum (small intestine) or the ascending and transverse colon of the large intestine, which together comprise the major volume of the alimentary canal.
Manometry requires that a long tube be inserted into the digestive tract and remain in place for times which vary from five hours for a routine diagnosis to twenty-four hours for a definitive assessment. Portable manometers have been designed for ambulatory use, but require the application of multiple pressure transducers placed within the gut, and that the orogastric tube be in place during “normal” activity. Stress and discomfort caused to the patient by insertion of the manometric probe can make measurement during “normal” activity difficult. Furthermore, such testing may be virtually intolerable if the patient is even moderately ill. The availability of better non-invasive methods for the diagnosis of disorders of motility and transport would greatly facilitate their management.
Two non-invasive biomagnetic techniques are known to the inventors to have been used to determine gut motility. The first measures the magnetic fields produced when the smooth muscles of the gut contract, producing electrical currents. The other measures the variation in strength of the magnetic fields produced by magnetic particles ingested and moved through the gut naturally. The Superconducting Quantum Interference Device (SQUID) measures minuscule magnetic fields and has been used to monitor both the biomagnetic signals produced by the gut muscles and the changing fields produced by magnetic sources ingested and moving through the gut. Although the SQUID magnetometer is extremely sensitive, it is also quite expensive to purchase and operate. SQUID sensors operate at liquid helium temperatures and must be housed in a liquid helium filled, vacuum-insulated chamber. Most SQUID sensors operate within magnetically-shielded enclosures. While some SQUID sensors are capable of being operated in open rooms, they are still extremely expensive. Multi-sensor devices are even more expensive. Moreover, the need for a magnetically-shielded room would create even greater expense.
SQUID magnetometers have been used in conjunction with ingested slurries of magnetic material to measure gut motility by monitoring the changes in magnetic field strength produced by the moving slurries. This technique requires less sensitivity than the technique of measuring biomagnetic fields produced by the contraction of the smooth muscles. In either case, the SQUID monitor requires that patients remain supine for the duration of the measurements.
The measurement of gut motility frequency is an important component of the diagnosis of gut motility disorders. Specifically, the pattern of frequencies measured is different in normal versus abnormal motility cases. The frequencies measured in normal cases are a function of location along the alimentary canal, ranging from relatively high frequencies (11 per minute) in the duodenum, to low frequencies (6 per minute) in the colon. The frequencies measured are apt to be varied by the feeding state of the patient, as well as other factors.
SUMMARY OF THE INVENTION
This invention provides both an apparatus for and method of measuring gut motility. The apparatus provided is non-invasive and comprises a magnet sized to be ingestible by a patient along with a compass external of the patient directionally sensitive to movement of the magnet in the patient's abdomen for monitoring of gut motility. In preferred form, the compass is an electronic flux-gate compass having an electronic directional output. This output may be stored in either internal or external memory and may be graphically recorded and displayed over a predetermined period of time.
Also in preferred form, use of a sufficiently long, but still ingestible, magnet will cause the device to be sensitive to rotational, as well as linear, movement within the patient's gut. Use of multiple compass detectors will enable location, as well as movement, to be determined, if desired.
The method of the present invention for measuring gut motility in a patient includes the steps of the patient swallowing an ingestible magnet, providing a compass external of the patient's abdomen for directionally sensing movement of the magnet in the patient's abdomen, and monitoring gut motility with the compass by measuring movement of the magnet.
In preferred form, the compass is an electronic flux-gate compass having an electronic output that may be recorded in internal or external memory and graphically displayed over a predetermined period of time. Use of an elongated magnet and the provision of multiple compasses, as described above, is another aspect of the present method.
Close study of the prior art described in the background of the invention section above should be carefully studied in order to put the present invention into proper perspective. Careful reading of the best mode for carrying out the invention and figures of the drawing, all of which are incorporated by reference into the disclosure of this invention, will reveal other aspects and features.
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“Magnetic Markers as a Noninvasive Tool to Monitor Gastrointestinal Transit,” by W. Weitschies et al., IEEE Transactions on Biomedical Engineering, Vo.41, No. 2, Feb. 1994, pp. 192-195.
“Measurement of Gastrointestinal Transit Time
Heitkemper Margaret
Nelson James A.
Pope Charles E.
Prakash N. Mani
Read Page
Bellamy Glenn D.
Fuller Benjamin R.
Thompson Jewel V.
University of Washington
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