US 4,380,237 A · Apparatus for making cardiac output conductivity measurements

Abstract

An improved catheter probe includes a conductivity sensor comprising four electrodes configured and spaced to be electrically coupled together by vascular fluids. A current source is provided for driving current through the vascular fluid between one pair of electrodes, and voltage sensing means is provided for measuring the voltage between the other pair of electrodes. In the preferred embodiment, the electrodes are closely spaced, substantially parallel electrodes oriented along the longitudinal direction of the catheter and transversely spaced apart by a distance which is small compared to the diameter of the catheter. The longitudinal length of the electrodes is chosen to be large as compared to the transverse spacing. The preferred current source is an isolated AC source, and the preferred voltage detection means is a phase sensitive voltage detector selectively responsive to the frequency and phase of the current source.

Claims12

Dependent claims

Apparatus for measuring the conductivity of vascular fluids within a vessel comprising:

a catheter having a predetermined diameter to fit within said vessel;
conductivity sensing means comprising at least two pairs of electrodes disposed on said catheter for contacting vascular fluids;
said electrodes comprising elongated conductive elements spaced apart by a predetermined distance which is both smaller than the diameter of the catheter and sufficiently small to reduce measurement fluctuations due to the fluid boundaries at the vascular walls, said conductive elements further having a length which is both larger than said predetermined distance and sufficiently large to reduce measurement fluctuations due to red blood cell density fluctuations;
means for supplying a known AC current between the electrodes of a first pair of electrodes;
and
means for measuring the voltage between the electrodes of the second pair in order to provide a measure of the conductivity of nearby vascular fluids.

3 more elements

Dependencies are inferred from the claim text.

Apparatus for making cardiac output conductivity measurements

Life of this patent

Apparatus for making cardiac output conductivity measurements

Life of this patent

Abstract

Claims12