Chemistry: analytical and immunological testing – Oxygen containing – Inorganic carbon compounds
Reexamination Certificate
1999-06-07
2001-07-24
Warden, Jill (Department: 1743)
Chemistry: analytical and immunological testing
Oxygen containing
Inorganic carbon compounds
C422S083000, C422S084000, C422S088000, C436S900000, C430S030000
Reexamination Certificate
active
06265221
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device for use in trapping and assaying
14
CO
2
in air exhaled by a person to which
14
C labelled compound has been administered, in particular
14
C labelled urea, and a corresponding method.
BACKGROUND OF THE INVENTION
Certain conditions and diseases can be indicated by analyzing exhaled air. For instance, air exhaled by persons suspected to be infected by the pathogenic bacteria
Helicobacter pylori
is analyzed by a variety of methods. According to one such method used clinically for a number of years, the patient is made to swallow an isotope-labelled urea preparation, in particular a preparation containing
14
C or
14
C labelled urea.
Helicobacter pylori
present in the gastrointestinal tract produces enzymes degrading the urea to ammonia/carbon dioxide. The gastro-intestinally formed carbon dioxide is transported to the lungs through the normal physiology of the body and exhaled together with other carbon dioxide formed by the body. The exhaled carbon dioxide is trapped by a suitable liquid, for instance, aqueous sodium hydroxide, which is examined with the aid of appropriate measuring instruments, for instance scintillation counters for detecting radioactive decay of
14
C.
The methods known in the art are relatively complicated and time consuming, and require the use of expensive and bulky apparatus. The provision of simple and cheap methods for use in decentralised health care has still not been adequately solved. There is thus a need for such methods and corresponding devices.
OBJECTS OF THE INVENTION
An object of the present invention is to provide a simple device for use in trapping and assaying of
14
C in air exhaled by a person under clinical investigation for a disease characterised by an increased metabolic rate for the transformation of
14
C labelled organic compounds, for instance of
14
C urea, to
14
CO
2
.
Another object of the present invention is to provide a method for clinical use of this device.
Further objects of the invention will become apparent from the following description of the invention and the appended claims.
SUMMARY OF THE INVENTION
According to the present invention is disclosed a device of the aforementioned kind comprising first and second substantially flat oblong duct forming elements joined to each other at their respective edges except for one of their short edges and forming a duct between them, the first duct forming element including a gas permeable matrix element for absorption of CO
2
, the device being provided with indicator means for detection of CO
2
absorption and a film element of low &bgr;-radiation absorptivity interposed or interposable between the matrix element and a &bgr;-radiation measuring instrument.
It is preferred for the film element to have a thickness of less than 0.05 mm, more preferably of less than 0.015 mm.
It is preferred for the matrix element to comprise a matrix, an absorbant for carbon dioxide, and an indicator for indication of carbon dioxide absorption.
It is preferred for the absorbant for carbon dioxide to comprise a strong base such as lithium hydroxide, sodium hydroxide, and calcium hydroxide.
It is preferred for the matrix element to be of such design and have such carbon dioxide absorption capacity as to become saturated with carbon dioxide within about one to two minutes by passage of the air exhaled by an adult person. The proper load of carbon-dioxide absorbant can be easily determined by experiment for matrix elements of various size and physical characteristics as well as chemical properties.
It is preferred for the indicator to be a pH indicator, preferably a pH indicator for visual indication of a pH change above pH 10. It is particularly preferred for the indicator to be selected form colour indicators changing from an uncoloured form at high pH to a coloured form at lower pH. Particularly preferred is the indicator phenolphthalein. Also preferred is the indicator tropaeolin.
The film forming element is advantageously provided with perforations to allow exhaled air to pass through it. The diameter of such perforations is preferably less than 2 mm, more preferably less than 1 mm, most preferably less than 0.5 mm. To balance the air flow through the device, perforations can also be arranged in one or both of the duct forming elements.
According to a first aspect of the invention it is preferred for the second duct forming element to have a through opening disposed opposite to the matrix element and being covered by the film element, the device preferably comprising a flexible flap secured at the closed short end and having a length sufficient for covering, in a first position, the through opening of the second duct forming element and, in a second position, the matrix element of the first duct forming element. The flap should be of a white reflective material. In its first position, the flap enhances the visibility of colour change by forming a standard reflective background to the matrix element. In its second position, it covers the now humid or wet matrix element and provides for hygienic handling of the device. It is preferred for the flap to be removable fixed at the second duct forming element in said first position. It is also preferred for the flap to be adhesively fixable to the first duct forming element in said second position. The means for adhesive fixation of the flap to the first duct forming element preferably are comprised by the means for its removable fixation at the second duct element.
According to a second aspect of the invention, it is preferred for the film element to have the form of a flexible flap secured at the closed short end and having a length sufficient for covering the matrix element of the first duct forming element. It is preferred for the film flap to be removably fixable at the second duct forming element.
According to a third aspect of the invention, the indicator means is disposed separate from the matrix element. The indicator means preferably comprises a pH indicator, in particular a pH indicator indicating by changed of colour a pH change above pH 10 and being disposed in a second matrix element for absorption of CO
2
.
The duct forming elements can be made in one piece, for instance by appropriate punching, folding and sealing of a piece of cardboard. They may also be joined at their edges partially or wholly by intermediate elements. The design of the device according to the invention provides for measurement of &bgr;-radiation from
14
C by comparatively inexpensive equipment, in particular a Geiger-Müller counter into a measuring cavity of which the device may be inserted.
According to the present invention is disclosed a method for trapping and assaying
14
C exhaled by a person under investigation for a disease or condition characterised by increased enzymic activity in the gastro-intestinal tract leading to carbon dioxide formation from an enzymatically degradable agent administered to said person, comprising:
making said person exhale into the one open short end of a device comprising first and second substantially flat oblong duct forming elements joined to each other at their respective edges except for said short end, the first duct forming element having an air-permeable matrix element covered by or coverable by a protective element with low &bgr;-radiation absorptivity, the matrix element including a carbon dioxide absorbant, the device further comprising indicator means for visual detection of CO
2
uptake by change of colour,
observing the indicator means to detect a colour change,
stopping exhalation into the device upon observation of the colour change,
optionally covering the matrix element with a protective element,
measuring &bgr;-radiation originating form the matrix element for a period of time by bringing the device into contact with an apparatus for &bgr;-radiation measurement,
comparing the number of registered decay events with that obtained from healthy persons.
Apparatus for detection of
14
C radiation include in particular Geiger-Müller counters.
Gakh Yelena G.
Noster System AB
Ostrolenk Faber Gerb & Soffen, LLP
Warden Jill
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