System and method for noninvasive hematocrit monitoring
US5372136A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 1, 1993 |
| Grant date | Dec 13, 1994 |
| Priority date | — |
| Expiry date | Feb 1, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/036
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A system for determining the hematocrit transcutaneously and noninvasively. Disclosed are a finger clip assembly and an earlobe clip assembly, each including at least a pair of emitters and a photodiode in appropriate alignment to enable operation in either a transmissive mode or a reflectance mode. At least two, and preferably three, predetermined wavelengths of light are passed onto or through body tissues such as the finger, earlobe, or scalp, etc. and the extinction of each wavelength is detected. Mathematical manipulation of the detected values compensates for the effects of body tissue and fluid and determines the hematocrit value. If a fourth wavelength of light is used which is extinguished substantially differently by oxyhemoglobin and reduced hemoglobin and which is not substantially extinguished by plasma, then the blood oxygen saturation value, independent of hematocrit, may be determined. It is also disclosed how to detect and analyze multiple wavelengths using a logarithmic DC analysis technique. Then a pulse wave is not required so, this method may be utilized in states of low blood pressure or low blood flow.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.