Apparatus and method for initiating cardiac output computations

In an apparatus for measuring cardiac output flow rate by introducing into the bloodstream of a subject a predetermined quantity of an indicator dye having a known detectable absorption characteristic different from that of said blood and monitoring the changes in light absorption of the blood at a location downstream from the point of introduction, including blood light absorption sampling means for generating time dependent signals representative of the varying blood light absorption at said location as said indicator travels through the bloodstream relative to said location, said signals defining a luminous transmission curve, computing means for estimating the area bounded by said luminous transmission curve and a baseline of light absoprtion subsequent to a first point in time, the improvement comprising:

• (a) comparing means for comparing successive signals;
• (b) means responsive to said comparing means for designating as said baseline, the light absorption corresponding to the first signal that is followed by a predetermined plurality of signals each representing a successively decreasing level of light detection, said first signal representing light absorption at said first time;
• and
• (c) means for initiating said computing means in response to designating said baseline of light absorption.

A method of measuring cardiac output comprising:

• (a) introducing a known volume of an indicator at a known temperature into the blood stream of a subject;
• (b) sensing blood temperature at a specified location within said subject;
• (c) sampling said blood temperature at predetermined intervals to form a blood temperature profile;
• (d) comparing successive blood temperature values;
• (e) designating as a baseline temperature the first temperature sampled subsequent to introducing the indicator which is followed by a predetermined plurality of successively decreasing blood temperatures, wherein said first temperature corresponds to a first time;
• and
• (f) estimating cardiac output by steps including integrating the area between said baseline temperature and said blood temperature profile over a specified period commencing with said first time.

A method of measuring cardiac output comprising:

• (a) introducing into the bloodstream of a subject a known volume of an indicator dye having a detectable light absorption characteristic different from that of the subject's blood;
• (b) detecting blood light absorption at a specified location within said subject;
• (c) sampling said blood light detection at predetermined intervals to form a luminous transmission curve;
• (d) designating as a baseline the first blood light absorption value sampled subsequent to introducing the dye which is followed by a predetermined plurality of successively decreasing light absorption detection signals, wherein said first light absorption signal corresponds to a first time;
• and
• (e) estimating cardiac output by steps including estimating the area between said baseline and said luminous transmission curve over a specified period commencing with said first time.