System and method of impedance cardiography monitoring
US5443073A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 13, 1993 |
| Grant date | Aug 22, 1995 |
| Priority date | — |
| Expiry date | May 13, 2013 |
Classification
- Technology area (CPC A)Human Necessities
- CPC primaryA61B5/7257
- WIPO fieldMedical technology
- WIPO sectorInstruments
Abstract
Cardiac monitoring is disclosed in which thoracic impedance and EKG signals are gathered and processed for improved resolution and accuracy. EKG signals are adaptively processed by digitizing, filtering, differentiating and raising the resultant differential by a power greater than one to emphasize changes in the slope of the EKG signal. Blocks of the thus processed EKG data are analyzed to identify peak amplitude and to compare spacing between peak amplitudes adaptively to more accurately identify R wave peaks. Stroke volume is determined from a thoracic impedance signal and its time derivative. Preferably, a time-frequency distribution is taken of the time derivative thoracic impedance signal after low- and high-pass filtering to identify B and X wave events in the signal which are used to determine ventricular ejection time and dZ/dt.sub.min for a determination of heart stroke volume by conventional methods. Alternatively, stroke volume is determined by a new relationship between a product of a pair of absolute impedances simultaneously sensed on opposing sides of a patient's heart at the peak of a heartbeat.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.