System for assessing endothelial function

A method of comparing tissue perfusion related values comprising:

• (a) applying thermal energy to the skin surface and the adjacent capillary bed of a subject and detecting the thermal response to the application of thermal energy;
• (b) producing signals functionally related to the thermal energy applied by said applying step and the thermal response to the application of thermal energy;
• (c) calculating a perfusion related value using the signals produced by step (b);
• (d) storing the perfusion related value obtained by step (c);
• (e) challenging blood flow to the skin surface and capillary bed to which thermal energy was applied by step (a);
• (f) repeating steps (a) through (c) for obtaining a perfusion related value affected by step (e);
• and
• (g) comparing the perfusion related value stored by step (d) and perfusion related value obtained by step (f).

A method for comparing tissue perfusion related values comprising:

• (a) locating a thermal transducer on the skin surface of a subject;
• (b) applying to said transducer pressure sufficient to produce thermal contact between said transducer and the skin surface and insufficient to produce substantial collapse of capillaries in the capillary bed adjacent the skin surface;
• (c) energizing said transducer for causing the temperature of the capillary bed to rise in an arbitrarily selected manner as a function of time;
• (d) calculating at least one selected intrinsic thermal property of the capillary bed using thermal data obtained at a first time period;
• (e) calculating a value related to tissue perfusion of the capillary bed using said at least one calculated intrinsic thermal property and thermal data obtained at a second time period, the effects of flow in the capillary bed at said second time period being greater than the effects of flow in the capillary bed at said first time period;
• (f) introducing a change to a selected physiological parameter related to tissue perfusion;
• (g) repeating steps (c) through (e);
• and
• (h) comparing a calculated perfusion related value obtained during a first physiological condition prior to said introducing step to a second calculated perfusion related value resulting from said introducing step.

A method for assessing endothelial function in a living subject comprising the steps of:

• determining an initial tissue perfusion related value at a selected location on the body of a subject;
• constricting the blood flow to the selected location for a time interval;
• releasing the constriction of blood flow to the selected location at the end of the time interval;
• and
• comparing the initial tissue perfusion related value to the tissue perfusion related value resulting from said releasing step.

A method for assessing a physiological parameter related to tissue perfusion comprising the steps of:

• determining a tissue perfusion related value in a capillary bed at a selected location on the body of a subject;
• subsequent to determining the tissue perfusion value at said selected location, challenging blood flow to said capillary bed for a time interval;
• releasing the challenge to blood flow to said capillary bed upon expiration of said time interval;
• determining a tissue perfusion related value in said capillary bed resulting from said releasing step;
• and
• comparing the results of the first said determining step and the second said determining step.

A method for non-invasively assessing endothelial function in a living subject comprising:

• placing a thermistor on the skin surface at a selected location on the body of a subject;
• applying to said thermistor pressure effective to establish thermal contact between said thermistor and the skin surface at the selected location and ineffective to significantly impair blood flow in the capillary bed adjacent the skin surface at the selected location;
• transferring thermal energy from said thermistor to said capillary bed;
• quantifying tissue perfusion in said capillary bed as a function of the dissipation from said capillary bed of thermal energy transferred by said transferring step;
• subsequent to said quantifying step constricting blood flow to said capillary bed for a time interval;
• releasing the constriction of blood flow to said capillary bed upon expiration of said time interval;
• upon said releasing step transferring thermal energy from said thermistor to said capillary bed;
• quantifying tissue perfusion in said capillary bed as a function of the dissipation from said capillary bed of thermal energy transferred by the second said transferring step;
• and
• comparing the results of the first said quantifying step and the second said quantifying step.

A method for assessing a physiological parameter related to tissue perfusion comprising the steps of:

• placing a thermal transducer in contact with the skin surface at a selected location on the body of a subject for facilitating the transmission of thermal energy between the capillary bed adjacent said skin surface and said transducer;
• applying to said transducer pressure effective to establish thermal contact between said transducer and said skin surface and ineffective to significantly impair blood flow in said capillary bed;
• transferring thermal energy from said transducer to said capillary bed;
• quantifying tissue perfusion in said capillary bed as a function of the dissipation from said capillary bed of thermal energy transferred by said transferring step;
• subsequent to said quantifying step constricting blood flow to said capillary bed for a time interval;
• releasing the constriction of blood flow to said capillary bed upon expiration of said time interval;
• upon said releasing step transferring thermal energy from said transducer to said capillary bed;
• quantifying tissue perfusion in said capillary bed as a function of the dissipation from said capillary bed of thermal energy transferred by the second said transferring step;
• and
• comparing the results of the first said quantifying step and the second said quantifying step.

A method of assessing a physiological characteristic of a living subject comprising the steps of;

• assessing peripheral tissue perfusion;
• and
• accessing a model relating peripheral tissue perfusion to the physiological characteristic;
• and
• comparing the results of said assessing step and the model accessed in the accessing step.

A method of assessing a physiological characteristic of a living subject comprising the steps of:

• assessing peripheral tissue perfusion as a proxy for said physiological characteristic;
• challenging the peripheral tissue perfusion assessed;
• assessing the changed peripheral tissue perfusion resulting from said challenging step;
• and
• comparing the results of the first said assessing step and the second said assessing step.

A method of assessing endothelial function of a subject comprising the steps of:

• sensing a peripheral tissue perfusion value at a selected location;
• storing the peripheral tissue perfusion value obtained by said sensing step;
• challenging blood flow to the selected location;
• sensing the changed peripheral tissue perfusion value at the selected location resulting from said challenging step;
• and
• calculating data indicative of systemic endothelial function using the stored peripheral tissue perfusion value and the peripheral tissue perfusion value resulting from the second said sensing step.

Apparatus for assessing endothelial function comprising:

• means for assessing peripheral tissue perfusion at a selected site on the body of a subject;
• a model relating peripheral tissue perfusion values to endothelial function;
• and
• a data processor correlating perfusion values from said assessing means with perfusion values provided by said model for obtaining values relating to endothelial function.

Apparatus for assessing endothelial function comprising:

• means for challenging blood flow at a selected site on the body of a subject for a time interval;
• means for assessing tissue perfusion at said site before and after a challenge to blood flow at said site;
• and
• a data processor for comparing tissue perfusion before and after a challenge to blood flow at said site for obtaining values related to endothelial function of the subject.

A system for comparing perfusion related values comprising:

• thermal transducer means for applying thermal energy to the skin surface of a subject and detecting the thermal response to the application of thermal energy;
• means for applying to said transducer means pressure sufficient to produce thermal contact between said transducer means and the skin surface of a subject and insufficient to produce substantial collapse of capillaries in the capillary bed adjacent the skin surface;
• means for producing signals functionally related to the thermal energy applied by said transducer means and the thermal response to the application of thermal energy;
• data processing. means for calculating a tissue perfusion related value using the signals produced by said signal producing means;
• data storage means for storing perfusion related data obtained during a first physiological condition related to tissue perfusion;
• and
• means for comparing perfusion related data stored by said data storage means and perfusion related data obtained during a second physiological condition related to tissue perfusion.

A system for comparing tissue perfusion related values comprising:

• thermal transducer means for applying thermal energy to the skin surface of a subject and detecting the thermal response to the application of thermal energy;
• means for applying to said transducer means pressure sufficient to produce thermal contact between said transducer means and the skin surface of a subject and insufficient to produce substantial collapse of capillaries in the capillary bed adjacent the skin surface;
• means for causing the temperature of the capillary bed to rise in an arbitrarily selected manner as a function of time;
• means for calculating at least one selected intrinsic thermal property of the capillary bed using data obtained at a first time period;
• means for calculating a value related to tissue perfusion of the capillary bed using data obtained at a second time period and said at least one calculated intrinsic thermal property, the effects of flow in the capillary bed at said second time period being greater than the effects of flow in the capillary bed at said first time period;
• and
• means for comparing a perfusion related value obtained during a first physiological condition related to tissue perfusion to a second perfusion value obtained during a subsequent physiological condition related to tissue perfusion.

A thermal transducer comprising:

• transducing means for applying thermal energy to tissue and detecting the thermal response of tissue to the application of thermal energy;
• a support circumscribing a central space and forming a tissue contacting surface;
• and
• means for mounting said transducing means within said central space in a position for contact with tissue when said surface is in contact with tissue and, when said surface is in contact with tissue, transmitting to said transducing means pressure sufficient to establish effective thermal contact between said transducing means and tissue in contact therewith and insufficient to cause substantial collapse of capillaries and vessels in the tissue in effective thermal contact with said transducing means.

A non-invasive thermal probe comprising;

• transducing means for applying thermal energy to tissue and detecting the thermal response of tissue to the application of thermal energy;
• support means surrounding said transducing means and spaced therefrom outside the direct thermal response zone of said transducing means;
• and
• means for mounting said transducing means within said surrounding support means and positioning an operative surface of said transducing means for contact with tissue when said support means is in contact with tissue;
• said mounting means comprising
• means for pressing said transducing means to the surface of tissue when said support means is in contact with tissue for producing effective thermal contact between said transducing means and the surface of the tissue contacted and producing insufficient contact between said transducing means and the surface of the tissue contacted to cause substantial collapse of capillaries and vessels within the direct thermal response zone of said transducing means.

A non-invasive thermal probe comprising:

• transducer means for contacting subject tissue and facilitating the transmission of thermal energy between the subject tissue and said transducer means;
• means supporting said transducer means defining loci for contacting the surface of said tissue around said transducer means outside the direct thermal response zone of said transducing means when said transducer means is in contact with the subject tissue;
• and
• means on said supporting means for transmitting to said transducing means, when said loci are in contact with the surface of tissue, pressure sufficient to establish effective thermal contact between said transducing means and tissue in contact therewith and insufficient to cause substantial collapse of capillaries and vessels in the tissue in effective thermal contact with said transducing means.