Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
198 words
Apparatus for continuously monitoring a cardiac output of a heart, comprising: (a) a catheter having a plurality of lumens that extend generally between a proximal end and a distal end of the catheter, the distal end of the catheter being insertable into a heart through a cardiovascular system; (b) means for supplying a periodically varying, temperature modifying input signal to a portion of the catheter that is spaced apart from its distal end; (c) a blood temperature sensor disposed adjacent the distal end of the catheter, said temperature sensor being provided to produce a blood temperature signal that is indicative of a temperature of blood flowing from the heart; (d) means for determining power transferred by the temperature modifying input signal, said means for determining producing a corresponding periodically varying power signal that is indicative of said power transferred, which corresponds to the input signal; (e) a phase comparator for determining a difference in phase between the periodically varying power signal and the periodically varying temperature signal; and (f) control means for determining the cardiac output of the heart as a function of the power signal, the blood temperature signal, and the difference in phase between said signals.
Claim 2
Dependent Claim
198 words
Apparatus for continuously monitoring a cardiac output of a heart, comprising: (a) a catheter having a plurality of lumens that extend generally between a proximal end and a distal end of the catheter, the distal end of the catheter being insertable into a heart through a cardiovascular system; (b) means for supplying a periodically varying, temperature modifying input signal to a portion of the catheter that is spaced apart from its distal end; (c) a blood temperature sensor disposed adjacent the distal end of the catheter, said temperature sensor being provided to produce a blood temperature signal that is indicative of a temperature of blood flowing from the heart; (d) means for determining power transferred by the temperature modifying input signal, said means for determining producing a corresponding periodically varying power signal that is indicative of said power transferred, which corresponds to the input signal; (e) a phase comparator for determining a difference in phase between the periodically varying power signal and the periodically varying temperature signal; and (f) control means for determining the cardiac output of the heart as a function of the power signal, the blood temperature signal, and the difference in phase between said signals.
Claim 3
Dependent Claim
61 words
The apparatus of claim 1, wherein the means for supplying comprise a source of an electrical current connected by a plurality of leads to a resistor disposed in the portion of the catheter spaced apart from its distal end, said input signal comprising a periodically varying electrical current that is applied to heat the resistor and any blood around the resistor.
Claim 4
Dependent Claim
40 words
The apparatus of claim 2, wherein the electrical current flowing through the resistor dissipates power and wherein the means for determining power transferred comprise means for determining the power dissipated in the resistor by the electrical current flowing through it.
Claim 5
Dependent Claim
43 words
The apparatus of claim 1, wherein the means for supplying comprise a pump that delivers a temperature-conditioned fluid through a closed loop fluid flow path defined by the lumens of the catheter, said pump cycling on and off periodically at a predefined frequency.
Claim 6
Dependent Claim
99 words
The apparatus of claim 4, wherein the means for determining power transferred comprise a first temperature sensor that monitors a temperature of the temperature-conditioned fluid pumped into the catheter, a second temperature sensor that monitors a temperature of the temperature-conditioned fluid as it returns from the heart, and means for determining a rate of flow of said fluid, the control means determining the power transferred as a function of the difference in temperature of the temperature-conditioned fluid monitored by the first and the second temperature sensors, and of the rate of flow of the temperature-conditioned fluid in the catheter.
Claim 7
Dependent Claim
30 words
The apparatus of claim 4, wherein the means for supplying further comprise a fluid chiller that cools the temperature conditioned fluid substantially below a temperature of blood entering the heart.
Claim 8
Dependent Claim
20 words
The apparatus of claim 4, wherein the fluid is heated substantially above a normal temperature of blood entering the heart.
Claim 9
Dependent Claim
74 words
The apparatus of claim 1, wherein the cardiac output is defined by an equation as follows: CO=|P(ω)|*COSΔΦ/(|T(ω).vertline.*Cb) where: CO=the cardiac output; P(ω)=the power transferred by the input signal, which varies at an angular frequency ω; ΔΦ=the difference in phase between the power signal and the blood temperature signal; T(ω)=the blood temperature indicated by the blood temperature signal, which varies at the angular frequency ω; and Cb=a specific heat times density constant for the blood.
Claim 10
Dependent Claim
35 words
The apparatus of claim 1, further comprising bandpass filter means for filtering the power signal and the blood temperature signal to filter out frequencies different from a frequency at which the input signal periodically varies.
Claim 11
Dependent Claim
32 words
The apparatus of claim 1, further comprising means for compensating for a phase shift error in the blood temperature signal due at least in part to a thermal mass of the catheter.
Claim 12
Dependent Claim
31 words
The apparatus of claim 1, wherein the control means compensate for an attenuation of the blood temperature signal by the catheter and the blood temperature sensor, in determining the cardiac output.