Patent ID: 7806830

Claim:
An apparatus for determining stroke volume by bioimpedance from a patient, comprising: two or more spaced apart alternating current flow electrodes positionable on a patient; two or more spaced apart voltage sensing electrodes positionable on the patient and between the alternating current flow electrodes; an alternating current source electrically connected to the alternating current flow electrodes; a voltmeter electrically connected to the voltage sensing electrodes; a processing unit in communication with the voltage sensing electrodes, wherein the processing unit is capable of using a voltage sensed by the voltage sensing electrodes to calculate a mean value of a second time-derivative of a cardiogenically induced impedance variation of the patient and to determine therefrom a stroke volume of the patient; wherein the processing unit calculates the mean value of the second time-derivative of the cardiogenically induced impedance variation as a peak rate of change of the cardiogenically induced impedance variation divided by a time to peak value of the cardiogenically induced impedance; and wherein the time to peak value is a selected time value at least as great as 0.01 seconds and no greater than 0.1 seconds.