Ear oximetry process and apparatus
First Claim
1. A process for determining the value of oxygen saturation of the blood of a subject, comprising:
- mounting an earpiece on the ear lobe of the subject, said earpiece comprising light directing means and light intensity detecting means and being arranged such that the light directing means is on one side of said ear lobe and the light detecting means is on the other side of said ear lobe;
directing a first ray of light, from a first light source, at a first frequency at said light directing means;
directing a second ray of light, from a second light source, at a second frequency at said light directing means;
whereby said rays are directed, by said light directing means, to said ear lobe and transmitted through said ear lobe, and the light intensities of the light rays transmitted through the ear lobe at said first and second frequencies are detected, by said light detecting means, and converted, in said light detecting means, to electrical signals representative of said light intensities;
differentiating, with a differentiating means, said electrical signals representative of said light intensities of said first and second frequencies respectively;
providing said differentiated signals to a processor means, said processor means comprising a set of predetermined coefficients;
and processing, in said processor means, said differentiated signals in association with said predetermined coefficients to obtain said value of oxygen saturation.
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Accused Products
Abstract
The invention relates to a non-invasive oximetry process for determining the value of oxygen saturation of the blood of a subject. In some ear oximetry processes, light at two or more frequencies is transmitted through the ear lobe or pinna of the ear of a subject, and the intensity of the transmitted light is measured on the other side of the ear lobe. These processes are affected by such variables as depth of blood in the ear lobe or pinna and differences in the total hemoglobin concentration in the blood. Applicant has discovered that inaccuracies caused by these variables can be eliminated or greatly reduced by taking the derivative of the intensity of the transmitted light, and processing the values of these derivatives in association with a set of predetermined pseudo coefficients by applying these to newly developed relationships disclosed in the specification. The result of such processing yields the value of oxygen saturation of the blood of the subject. An apparatus for carrying out the inventive process is also taught.
295 Citations
21 Claims
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1. A process for determining the value of oxygen saturation of the blood of a subject, comprising:
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mounting an earpiece on the ear lobe of the subject, said earpiece comprising light directing means and light intensity detecting means and being arranged such that the light directing means is on one side of said ear lobe and the light detecting means is on the other side of said ear lobe; directing a first ray of light, from a first light source, at a first frequency at said light directing means; directing a second ray of light, from a second light source, at a second frequency at said light directing means; whereby said rays are directed, by said light directing means, to said ear lobe and transmitted through said ear lobe, and the light intensities of the light rays transmitted through the ear lobe at said first and second frequencies are detected, by said light detecting means, and converted, in said light detecting means, to electrical signals representative of said light intensities; differentiating, with a differentiating means, said electrical signals representative of said light intensities of said first and second frequencies respectively; providing said differentiated signals to a processor means, said processor means comprising a set of predetermined coefficients; and processing, in said processor means, said differentiated signals in association with said predetermined coefficients to obtain said value of oxygen saturation. - View Dependent Claims (2, 3)
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4. Apparatus for determining the oxygen saturation of the blood of a subject and used in association with an earpiece for mounting on the ear of the subject, the earpiece comprising light directing means and light intensity detecting means and being arranged such that the light detecting means is mounted on one side of the ear lobe and the light directing means is mounted on the other side of the ear lobe, and means for directing rays of light at a first frequency and rays of light at a second frequency at said light directing means whereby said rays are directed at the ear lobe and transmitted through the ear lobe and the light intensity of the light transmitted through the ear lobe at said first and second frequencies is detected to provide electrical signals representative of said light intensities;
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said apparatus comprising; differentiating means for differentiating said electrical signals representative of said light intensities at said first and second frequencies; processor means, comprising a set of predetermined coefficients and adapted to process said differentiated signals in association with said predetermined coefficients to obtain said value of oxygen saturation. - View Dependent Claims (5, 6, 7)
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8. A process for determining the value of oxygen saturation of the blood of a subject, comprising:
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mounting a source of light adjacent the subject such that light from the source is directed at an area of skin surface on the subject; disposing a light detector means relative to said source of light such that light passing from the source to the light means detector will contact said area; directing a first ray of light, from said source of light, at a first frequency at said area; directing a second ray of light, from said source of light, at a second frequency at said area; detecting, with said light detector means, the light intensity of the rays of light after they contact said area to provide electrical signals representative of the light intensities at said first and second frequencies; differentiating, with a differentiating means;
said electrical signals representative of said light intensities of said first and second frequencies respectively;providing said differentiated signals to a processor means, said processor means comprising a set of predetermined coefficients; and processing, with said processor means, said differentiated signals in association with said predetermined coefficients to obtain said value of oxygen saturation. - View Dependent Claims (9, 10)
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11. A process for determining the value of oxygen saturation of the blood of a subject, comprising:
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mounting a source of light such that light from the source is directed at an area of skin surface on the subject to be reflected by said area of skin surface; disposing a light detector means relative to said area such that light reflected from said area will be directed at said detector means; directing a first ray of light, from said source of light, at a first frequency at said area and, thereby, by reflectance, at said detector means; directing a second ray of light, from said source of light, at a second frequency at said area and, thereby, by reflectance, at said detector means; detecting, with said light detector means, the light intensity of the reflected rays of light to provide electrical signals representative of the light intensities at said first and second frequencies; differentiating, with a differentiating means, said electrical signals representative of said light intensities at said first and second frequencies respectively; providing said differentiated signals to a processor means, said processor means comprising a set of predetermined coefficients; and processing, with said processor means, said differentiated signals in association with said predetermined coefficients to obtain said value of oxygen saturation. - View Dependent Claims (12, 13, 14, 15)
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16. Apparatus for determining the oxygen saturation of the blood of a subject and used in association with a source of light and light intensity detecting means, the source of light being mounted such that it is directed at an area of skin surface of the subject, the source of light and the light intensity detecting means being arranged relative to each other such that light passing from the source to the detecting means will contact said area, and means in said source of light for transmitting the light at a first frequency and at a second frequency, said detecting means providing electrical signals representative of said light intensities;
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said apparatus comprising; differentiating means for differentiating said electrical signals representative of said light intensities at said first and second frequencies; processor means, comprising a set of predetermined coefficients and adapted to process said differentiated signals in association with said predetermined coefficients to obtain said value of oxygen saturation. - View Dependent Claims (17, 18)
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19. Apparatus for determining the oxygen saturation of the blood of a subject and used in association with a source of light, which source of light directs rays of light at an area of skin surface of the subject for reflection from the area, light intensity detecting means being disposed such that light rays reflected from said area will be directed at said detecting means, means in said source of light for transmitting rays of light at a first frequency and at a second frequency, whereby the light intensity of the light rays reflected from said area at said first and second frequencies is detected to provide electrical signals representative of said light intensities;
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said apparatus comprising; differentiating means for differentiating said electrical signals representative of said light intensities at said first and second frequencies; processor means, comprising a set of predetermined coefficients and adapted to process said differentiated signals in association with said predetermined coefficients to obtain said value of oxygen saturation. - View Dependent Claims (20, 21)
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Specification