Method and apparatus for noninvasively determining hematocrit
US5526808A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 20, 1995 |
| Grant date | Jun 18, 1996 |
| Priority date | — |
| Expiry date | Apr 20, 2015 |
Classification
- Technology area (CPC A)Human Necessities
- CPC primaryA61B5/4869
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus for noninvasively determining hematocrit utilizing the frequency dependent electrical impedance characteristics of whole blood by electrically stimulating a patient body portion containing a pulsatile vascular compartment with a constant current source at two selected frequencies, one of which is high enough that the capacitive nature of erythrocytes will significantly affect the magnitude of the impedance of the blood. Sensed voltage across the stimulated body portion at the two frequencies is representative of the corresponding magnitudes, and the method further includes detecting the signal envelopes of the sensed voltages, isolating and converting the pulsatile components of the signal envelopes to the digital domain, normalizing each isolated converted pulsatile component against the voltage baseline of its carrier waveform and creating a ratio of the normalized isolated pulsatile components representative of the patient's hematocrit. The ratio is indexed to a look-up table constructed from clinical studies correlating such ratios at the two selected frequencies to hematocrit, and the hematocrit corresponding to the created ratio is displayed. A pluralit…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.