Surgery – Diagnostic testing – Respiratory
Patent
1999-05-14
2000-08-08
O'Connor, Cary
Surgery
Diagnostic testing
Respiratory
73 233, A61B 508
Patent
active
060994800
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates generally to apparatus for measuring the percentage of a chosen gas, a NO-gas or NO.sub.2 -gas, in a gas mixture.
The invention finds suitable application in evaluating the percentage of NO or NO.sub.2 in the expiration air or inspiration air of a living being, preferably a human being.
More particularly, the invention relates to the type of apparatus in which a volume of expiration air or inspiration air suitable for test purposes is led to measuring equipment from an outlet in the immediate vicinity of said being, via a hose or like conduit.
In this application, the measuring equipment may include a measuring chamber which is placed under a sub-pressure and to which ozone gas (O.sub.3) is delivered, wherewith the NO-content will react with the ozone gas to form NO.sub.2 and light, and also a light-measuring unit adapted evaluate the number of photons or the like in the measuring chamber and to calculate in a calculating unit the predominating gas in the expiration air on the basis of said evaluation.
For the sake of simplicity, the following description will be made solely with reference to its application in respect of expiration air.
DESCRIPTION OF THE BACKGROUND ART
Several different designs of apparatus of the kind defined in the introduction are known to the art. Apparatus on which the present invention is based will be described summarily hereinafter with reference to FIGS. 1 and 2.
In this known construction, a chamber window that delimits the measuring chamber is comprised of a clear glass plate and the total chemiluminescence generated in the measuring chamber is measured.
It is also known, by way of an alternative, to incorporate a filter in the chamber window or to provide the window with a filter. The filter used in this respect is one that will extinguish light wave lengths shorter than 620 nm. Such a filter is used in NO/NO.sub.2 analysis processes.
It is therewith known to deliver the gas mixture and the ozone gas continuously to the measuring equipment and particularly to the measuring chamber, through a respective hose-mounted throttle valve. Alternatively, the gas mixture can be delivered discontinuously, by controlling a number of valves in accordance with the expiration cycle.
The International Patent Publication WO 95/02181 (PCT/SE 94/00659) teaches a system of establishing the NO-content of the expiration air from a living being.
Since the present invention is based on the ability to evaluate relatively small amounts of nitrogen oxide (NO) present in a gas mixture, it can be mentioned that it is also known to evaluate the nitrogen oxide content of a gas with the aid of chemiluminescence, with the aid of, for instance, NO/NO.sub.2 -analyzers used by Monitor Labs, 8840, and marketed by Oleico AB, Lidingo, Sweden.
The presence of nitrogen oxide (NO) can also be shown by collection in distilled water to which iron (II) sulphate has been added, freeze-drying the mixture to dryness and thereafter shown as nitrite, either with the Diazo-reaction according to Martin, et al or with a Nitur-test qualitative nitrite stick.
Other known measuring instruments that operate with mass-spectrography can be used for this purpose.
A common feature of all earlier known methods of evaluating the NO-content of a gas mixture is that it is difficult to evaluate the time-wise short variation of the NO-content, for instance during a single expiration cycle.
SUMMARY OF THE PRESENT INVENTION
Technical Problems
When considering the earlier standpoint of techniques as described above, and as described in more detail hereinafter with reference to FIGS. 1 and 2, it will be seen that a technical problem resides in creating conditions that will enable the NO-content or NO.sub.2 -content of a gas mixture to be measured reliably in a measuring chamber, even in the case of very small NO- or NO.sub.2 -concentrations, without the gas to be measured adhering to the material of the sampling tube or channel to any appreciable extent.
It will also be seen that a techn
REFERENCES:
patent: 5447165 (1995-09-01), Gustafsson
patent: 5795787 (1998-08-01), Silkoff et al.
patent: 5922610 (1999-07-01), Alving et al.
Aerocrine AB
Natnithithadha Navin
O'Connor Cary
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