Breath test analyzer

Details Breath test analyzer Breath test analyzer

1998-09-10

2001-02-13

O'Connor, Cary (Department: 3736)

Surgery

Diagnostic testing

Respiratory

C600S529000, C436S811000, C424S084000, C128S898000

Reexamination Certificate

active

06186958

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to the field of analyzers of the breath of patients to detect the gastric by-products of various diseases and infections.
BACKGROUND OF THE INVENTION
Since the early 1950's, it has been known that the presence of bacterial organisms in the gastro-intestinal tract is accompanied by a high concentration of urease, which hydrolyses urea to form carbon dioxide and ammonia. These gases are detected in the subject's blood stream and ultimately, in the subject's breath, if he had been administered isotopically labeled urea. Such early results appear in reviews published by R. W. VonKorff et al. in Am. J. Physiol., Vol. 165, pp. 688-694, 1951, and by H. L. Kornberg and R. E. Davies in Physiol. Rev., Vol. 35, pp. 169-177, 1955.
Since these early experiments, it has been found that there exist, in addition to the bacterial infections initially studied, a significant number of medical conditions associated with disorders of the gastro-intestinal tract or metabolic or organ malfunctions, which are capable of detection by means of such simple breath tests. These breath tests are based on the ingestion of an isotopically labeled sample, which is cleaved by the specific bacteria or enzymic action being sought, or as a result of the metabolic function being tested, to produce labeled gaseous by-products. These by-products are absorbed in the blood stream, and are exhaled in the patient's breath, where they are detected by means of external instrumentation.
Though the early experiments were performed using the radioactive carbon-14 atom, the most commonly used atom in such test procedures today is the carbon-13 atom, which is a stable, non-radioactive isotope, present in a proportion of about 1.1% of naturally occurring carbon. The labeled substance contains the functional compound to be used in the test, with almost all of its
12
C atoms replaced by
13
C atoms. Enrichments of up to 99% of
13
C are typically used. This compound is cleaved enzymatically under the specific conditions being tested for, either during gastric absorption, or during gastro-intestinal transit, or during its metabolisation in other organs of the body. The cleavage product produced is
13
CO
2
, which is absorbed in the bloodstream and exhaled in the patient's breath together with the CO
2
naturally present. The breath sample is then analyzed, usually in a mass spectrometer or a non-dispersive infra-red spectrometer. The increased presence of
13
CO
2
is determined, as compared with the expected 1.1% of total CO
2
in healthy patient's breath, resulting from the metabolism of carbon compounds with the naturally occurring level of approximately 1.1% of carbon-13.
Though carbon-13 is the most commonly used isotopic replacement atom in such breath tests, other atoms which have been used include nitrogen-15 and oxygen-18. In addition, carbon-14 is still used in some procedures, but being radioactive, there are severe disadvantages both to its ingestion by the patient, and because of the storage, handling and disposal precautions required at the test site.
There are an increasing number of metabolic disorders, bacterial infections and organ malfunctions which can be diagnosed using such labeled substances for enabling breath tests. New applications are being proposed continuously, but among the more common currently in use are:
(a) The detection of
Helicobacter pylori
infections in the gastric and duodenal tracts, by means of the ingestion of
13
C-labeled urea and breath detection of an increased level of
13
CO
2
. It is also feasible to use
15
N-labeled urea, and to detect nitrogen-15 ammonia
15
NH
3
in the breath, but this test format is not currently in use. Gastric and duodenal ulcers, non-ulcer dyspepsia and gastritis have been shown to be related to the presence of
Helicobacter pylori
infections.
(b) The detection of fat malabsorption, such as is present in steatorrhea and Crohn's disease, by means of the ingestion of
13
C-labeled triolein or tripalmitin, and breath detection of an increased level of
13
CO
2
.
(c) Liver function evaluation (by monitoring the P450 enzyme activity), liver disease severity and detoxification activity by means of the ingestion of
13
C-labeled aminopyrin, methacitin or caffeine citrate (depending on the specific function being tested) and breath detection of an increased level of
13
CO
2
.
(d) The measurement of hepatic mitochondrial activity by means of the ingestion of
13
C-labeled octanoic acid, and breath detection of an increased level of
13
CO
2
.
(e) A check of hepatic mitochondrial function efficiency by means of the ingestion of
13
C-labeled ketoisocaproic acid, and breath detection of an increased level of
13
CO
2
.
(f) The quantification of functional liver mass by means of the ingestion of
13
C-labeled galactose, and breath detection of an increased level of
13
CO
2
.
(g) The testing of gastric emptying function by means of the ingestion of
13
C-labeled octanoic acid for the emptying rate of solids, or
13
C-labeled sodium acetate for the emptying rate of liquids, and breath detection of an increased level of
13
CO
2
(h) The determination of exocrine pancreatic insufficiency by means of the ingestion of a
13
C-labeled mixed triglyceride sample such as octanoil-1,3-distearin for checking the lipase function, or a
13
C-labeled sample of corn starch for checking the amylase function, and breath detection of an increased level of
13
CO
2
. The mixed triglyceride test is one of the tests used for detecting cystic fibrosis. For the evaluation of the digestion and absorption of medium-chain fatty acid triglycerides,
13
C-labeled trioctanoin is used in preference to the mixed triglyceride.
(i) The detection of bacterial overgrowth in the small intestine by means of the ingestion of
13
C-labeled glycolic acid or xylose, and breath detection of an increased level of
13
CO
2
.
(j) The testing of lactose or glucose intolerance, by means of the ingestion of
13
C-labeled lactose or glucose, and measurement of the speed of appearance of an increased level of
13
CO
2
in the breath.
Previously available tests for these illnesses generally involve drastically more invasive procedures, and are therefore much less patient compliant than the simple breath tests described above. Such procedures include gastro-endoscopy, with or without the removal of a tissue biopsy, biopsies of organs suspected of malfunction, blood tests to detect antibodies to suspected bacteria, blood biochemistry tests following ingestion of suitable compounds, and radiological tests, whether by gamma imaging of the organ function following ingestion or injection of a suitable gamma emitter, or by direct X-ray imaging or CT scanning. Furthermore, there are other disadvantages to the previously used tests, such as the fact that they rarely give real time information about the organ function or status being observed. In some cases, such as in the case of blood tests for antibodies of bacterial infections, they give historic results which may have no therapeutic relevance currently, since antibodies to a particular bacterium can remain in the body for up to 2 years from the date that the infection has been eradicated.
The above mentioned breath tests are completely non-invasive, and are executed in comparative real time, so that they have a great advantage over previously available tests, and their use is gaining popularity in the medical community, as evidenced by the fact that suitable isotopically labeled substances are currently available commercially from a number of sources.
However, in spite of the advantages of isotopically labeled breath tests, current instrumentation and procedures for performing it still have a number of serious drawbacks, which continue to limit its usefulness. The major disadvantage, which becomes apparent when a review of prior art breath test performance techniques and instrumentation is performed, is that none of the currently used techniques are sufficiently rapid to permit immediate

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