GB2131195A

GB2131195A - A fitter holder for a haemoglobin density comparator

Info

Publication number: GB2131195A
Application number: GB08230545A
Authority: GB
Inventors: Raymond Leonard Crutcher
Original assignee: DELPHI IND Ltd
Current assignee: DELPHI IND Ltd
Priority date: 1982-10-26
Filing date: 1982-10-26
Publication date: 1984-06-13

Abstract

Photometric haemoglobinometer is calibrated using a neutral density filter (6) held within a holder (4) of identical dimensions to the standard cuvette normally used with the meter. The holder has non-reflective internal surfaces. This enables the meter to be calibrated outside laboratory conditions. <IMAGE>

Description

SPECIFICATION Haemoglobin density comparator This invention relates to a method and apparatus for determining the haemoglobin value in a blood sample.

It is often useful to be able to determine quickly with some accuracy what the haemoglobin value of a blood sample is. There is therefore a demand for a reliable, portable haemoglobinometer suitable for use in the field by paramedics or other medical workers remote from a hospital. Such meters are already in use and generally work by measuring the amount of light of a specific wavelength passing through a sample of the blood in a standard cuvette.

However, there may be some difficulty in calibration of a portable, photometric haemoglobinometer.

The object of the present invention is to provide a simple means of calibrating a portable photometric haemoglobinometer.

In a first aspect, the present invention broadly consists in a holder for an optical filter, the holder comprising opaque walls of standard dimensions, defining a space within it for containing an optical filter.

In a second aspect the present invention broadly consists in a method of calibrating a photometric haemoglobinometer of the type arranged to take a standard cuvette of blood and to measure the amount of light from a standard light source passing through the cuvette, the method comprising the steps of placing a holder containing, not blood, but an optical filter into the haemoglobinometer, measuring the amount of light passing through the filter and comparing the reading with the standard haemoglobin density equivalent of the cuvette and filter.

The above gives a broad description of the present invention, a preferred form of which will now be described by way of example with reference to the accompanying drawings in which: Figure 1 illustrates a cuvette for use in haemoglobinometer; Figure 2 illustrates a holder of the present invention; and Figure 3 is a sectional view through the holder of Figure 2.

In its preferred form the present invention consists in a holder of the same external dimensions as a standard cuvette. The standard cuvette 1 is typically one centimeter square, with two clear polished, substantially parallel sides 2. The other two sides 3 are parallel, but have matt surfaces to prevent internal reflection and light scattering.

The holder 4, as illustrated in Figures 2 and 3, has the same external shape, but is opaque. It does, however, have an opening 5 in each side, preferably frusto-conical as shown to eliminate internal reflections. The opening 5 exposes the interior of the holder Light can therefore pass through the openings and through the interior of the holder. Within the interior of the holder is placed a strip of neutral density filter material 6.

The filter 6 may be formed of plastic, glass or other suitable light-transmitting material. However, glass or light-stabilised acrylic is preferred because of its resistance to degradation. The filter may comprise a strip of glass, vacuum coated by metal deposition, or stable dyed glass, or strips of gelatin wafers impregnated with carbon or colloidal silver.

When the filter 6 is placed in the holder, it is secured in place by an epoxy or other bonding or sealing material 7. The material is preferably black, or provided with a black coating, to eliminate any stray light reflections.

A series of standard filters may be supplied for use with the haemoglobinometer, each filter having been calibrated against a cyanmethaemoglobin standard. A suitable standard would be that provided by the Diagnostic Laboratories Limited of Oxford, England, who supply a cyanmethaemoglobin standard approved by the International Commitee for Haematology. The filter standard would normally be calibrated using a narrow band spectrophotometer, the preferred wave length being 540 nm.

The haemoglobinometer should use a light source of the same wavelength, although a wavelength of between 540 and 550 nm may be used for cyanmethaemoglobin. Wavelengths to either side of these figures may also be used, although they are less preferred. 450 nm is moving too far out of the green and into the yellow, however. 575 nm is suitable for oxyhaemoglobin.

A series of standard filters would be used to calibrate over a range of haemoglobin concentrations. Typically a filter with a transmissivity of 0.5 D would correspond to a cyanmethaemoglobin of 195 grams per litre, whereas a transmissivity of 0.4 D would correspond to a cyanmethaemoglobin density of 1.68 grams per litre.

Using a haemoglobinometer as supplied by Delphi Industries Ltd of Auckland, New Zealand, would mean that two standard filters would be sufficient to calibrate the instrument, since its characteristics do not vary significantly from linear.

Thus, the present invention provides means whereby an operator in isolated or adverse conditions can use a portable photometric haemoglobinometer and, with a supply of standard reference filters to coverthe range of normal blood densities, maintain the accuracy of the meter. The haemoglobinometer can thus be used just as readily in a jungle or desert or by a roving paramedic, as in an ordinary medical clinic.

Various modifications to the above may be used without departing from the scope of the present invention as broadly defined.

1. A holder for an optical filter, the holder comprising opaque walls ofstandard dimensions, defining a space within it for containing an optical filter.

2. A holder as claimed in claim 1 wherein the internal surfaces of the holder are matt.

3. A holder as claimed in claim 1 or 2, containing a neutral density filter.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Haemoglobin density comparator This invention relates to a method and apparatus for determining the haemoglobin value in a blood sample. It is often useful to be able to determine quickly with some accuracy what the haemoglobin value of a blood sample is. There is therefore a demand for a reliable, portable haemoglobinometer suitable for use in the field by paramedics or other medical workers remote from a hospital. Such meters are already in use and generally work by measuring the amount of light of a specific wavelength passing through a sample of the blood in a standard cuvette. However, there may be some difficulty in calibration of a portable, photometric haemoglobinometer. The object of the present invention is to provide a simple means of calibrating a portable photometric haemoglobinometer. In a first aspect, the present invention broadly consists in a holder for an optical filter, the holder comprising opaque walls of standard dimensions, defining a space within it for containing an optical filter. In a second aspect the present invention broadly consists in a method of calibrating a photometric haemoglobinometer of the type arranged to take a standard cuvette of blood and to measure the amount of light from a standard light source passing through the cuvette, the method comprising the steps of placing a holder containing, not blood, but an optical filter into the haemoglobinometer, measuring the amount of light passing through the filter and comparing the reading with the standard haemoglobin density equivalent of the cuvette and filter. The above gives a broad description of the present invention, a preferred form of which will now be described by way of example with reference to the accompanying drawings in which: Figure 1 illustrates a cuvette for use in haemoglobinometer; Figure 2 illustrates a holder of the present invention; and Figure 3 is a sectional view through the holder of Figure 2. In its preferred form the present invention consists in a holder of the same external dimensions as a standard cuvette. The standard cuvette 1 is typically one centimeter square, with two clear polished, substantially parallel sides 2. The other two sides 3 are parallel, but have matt surfaces to prevent internal reflection and light scattering. The holder 4, as illustrated in Figures 2 and 3, has the same external shape, but is opaque. It does, however, have an opening 5 in each side, preferably frusto-conical as shown to eliminate internal reflections. The opening 5 exposes the interior of the holder Light can therefore pass through the openings and through the interior of the holder. Within the interior of the holder is placed a strip of neutral density filter material 6. The filter 6 may be formed of plastic, glass or other suitable light-transmitting material. However, glass or light-stabilised acrylic is preferred because of its resistance to degradation. The filter may comprise a strip of glass, vacuum coated by metal deposition, or stable dyed glass, or strips of gelatin wafers impregnated with carbon or colloidal silver. When the filter 6 is placed in the holder, it is secured in place by an epoxy or other bonding or sealing material 7. The material is preferably black, or provided with a black coating, to eliminate any stray light reflections. A series of standard filters may be supplied for use with the haemoglobinometer, each filter having been calibrated against a cyanmethaemoglobin standard. A suitable standard would be that provided by the Diagnostic Laboratories Limited of Oxford, England, who supply a cyanmethaemoglobin standard approved by the International Commitee for Haematology. The filter standard would normally be calibrated using a narrow band spectrophotometer, the preferred wave length being 540 nm. The haemoglobinometer should use a light source of the same wavelength, although a wavelength of between 540 and 550 nm may be used for cyanmethaemoglobin. Wavelengths to either side of these figures may also be used, although they are less preferred. 450 nm is moving too far out of the green and into the yellow, however. 575 nm is suitable for oxyhaemoglobin. A series of standard filters would be used to calibrate over a range of haemoglobin concentrations. Typically a filter with a transmissivity of 0.5 D would correspond to a cyanmethaemoglobin of 195 grams per litre, whereas a transmissivity of 0.4 D would correspond to a cyanmethaemoglobin density of 1.68 grams per litre. Using a haemoglobinometer as supplied by Delphi Industries Ltd of Auckland, New Zealand, would mean that two standard filters would be sufficient to calibrate the instrument, since its characteristics do not vary significantly from linear. Thus, the present invention provides means whereby an operator in isolated or adverse conditions can use a portable photometric haemoglobinometer and, with a supply of standard reference filters to coverthe range of normal blood densities, maintain the accuracy of the meter. The haemoglobinometer can thus be used just as readily in a jungle or desert or by a roving paramedic, as in an ordinary medical clinic. Various modifications to the above may be used without departing from the scope of the present invention as broadly defined. CLAIMS

3. A holder as claimed in claim 1 or 2, containing a neutral density filter.

4. A holder for an optical filter, substantially as herein described with reference to Figures 2 and 3 of the accompanying drawings.

5. A method of calibrating a photometric haemoglobinometer of the type arranged to take a standard cuvette of blood and to measure the amount of light from a standard light source passing through the cuvette, the method comprising the steps of placing a holder containing, not blood, but an optical filter into the haemoglobinometer, measuring the amount of light passing through the filter and comparing the reading with the standard haemoglobin density equivalent of the cuvette and filter.

6. A method of calibrating a photometric haemoglobinometer, substantially as herein described with reference to Figures 2 and 3 of the accompanying drawings.