Patent ID: 8131354

Claim:
A method of estimating stroke volume of the heart, comprising: acquiring a first set of electrical data of the chest, using electrodes placed on skin around the chest, at a first phase of the cardiac cycle; estimating a first volume of the heart from the first set of electrical data; acquiring a second set of electrical data of the chest, using electrodes placed on skin around the chest, at a second phase of the cardiac cycle; estimating a second volume of the heart from the second set of electrical data; and using the difference between the first and second volumes of the heart to estimate the stroke volume of the heart; wherein estimating the first volume of the heart comprises generating a first impedance image of the chest from the first set of electrical data, and estimating the second volume of the heart comprises generating a second impedance image of the chest from the second set of electrical data, and generating the second impedance image of the chest comprises putting constraints on differences between the second impedance image and the first impedance image, but not constraining the volume of the heart to be the same in the first and second impedance images.