Method and apparatus for improved photoplethysmographic monitoring of oxyhemoglobin, deoxyhemoglobin, carboxyhemoglobin and methemoglobin
US5842979A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 14, 1997 |
| Grant date | Dec 1, 1998 |
| Priority date | — |
| Expiry date | Feb 14, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/314
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An improved method and apparatus for the photoplethysmographic monitoring of blood analyte parameters, specifically oxyhemoglobin, deoxyhemoglobin (reduced hemoglobin), carboxyhemoglobin and methemoglobin, uses a plurality of beams of light having different spectral contents to trans-illuminate the tissue of a patient. Received light is measured and the normalized differential absorption is used in a forward calibration equation to generate estimated relative blood analyte concentration values. Error in the blood analyte concentration values is minimized by applying constraints to the estimated analytes. Specifically, the constraints require that all relative analyte concentration values are greater than or equal to zero and sum to one hundred percent. An alternate method of applying constraints to the determination of the stabilized analyte concentration values reduces computation time by using an inverse calibration equation and substituting the inverse equation for the forward equation in the minimization process.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.