System and method for in-vivo hematocrit measurement using impedance and pressure plethysmography
US6766191B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | May 16, 2000 |
| Grant date | Jul 20, 2004 |
| Priority date | — |
| Expiry date | May 16, 2020 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B10/2941
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
The hematocrit of blood (i.e., the percentage of whole blood volume occupied by red blood cells) perfusing a finger is determined by stimulating the finger with two current frequencies, one relatively high (e.g., 10 MHZ) and the other relatively low (e.g., 100 KHz). Voltages induced in the finger in response to the two current frequencies are then captured and separated into baseline and pulsatile components. The hematocrit is determined as a function of the ratio of the high frequency pulsatile component to the low frequency pulsatile component, multiplied by the ratio of the square of the low frequency baseline component to the square of the high frequency baseline component. The volume of blood perfusing the body part at which hematocrit is to be measured may be increased on each pulse by the application of external pressure to the finger, such as by applying a pressure cuff to the finger. Assemblages including two pairs of electrodes are used to effect the determination of hematocrit. The assemblages may also include a component for applying pressure to the body part at which hematocrit is measured.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.