Norbert J Christman

US Patent:

51781549, Jan 12, 1993

Filed:

Sep 18, 1990

Appl. No.:

7/584319

Inventors:

James J. Ackmann - Wauwatosa WI
Norbert T. Christman - Wauwatosa WI
Thomas J. Ebert - Glendale WI

Assignee:

Sorba Medical Systems, Inc. - Milwaukee WI

International Classification:

A61B 50295

US Classification:

128713

Abstract:

Parameters of cardiac activity can be derived from detecting thoracic impedance changes in a patient. An excitation signal is applied between a first pair electrodes located on the patient's forehead and torso. The voltage across another pair of electrodes positioned between the first pair is sensed to provide a first signal representing the impedance. The derivative of the first signal produces a second signal. Samples of the second signal taken during a number of cardiac cycles are ensemble averaged to minimized respiratory artifacts. Different criteria, such as the relationship between the second signal and an electrocardiographic signal, are employed to accept segments of the second signal which occur during different cardiac cycles. Samples of the accepted second signal segments for a number of cardiac cycles are ensemble averaged to minimize respiratory artifacts. The ensemble averaged data is employed to calculate cardiac stroke volume and cardiac output.