Tonometry system for monitoring blood pressure

Claims

What is claimed is:

1. A method of noninvasively monitoring a patient's arterial blood pressure using a tissue stress sensor having a continuous diaphragm, comprising the steps of:

(A) placing the sensor against tissue adjacent a preselected artery;

(B) applanating the preselected artery, using the sensor to bear against the tissue adjacent the preselected artery;

(C) determining a monitoring portion on the sensor, said monitoring portion being a portion of the sensor that is best suited for acquiring blood pressure information given the location of the sensor relative to the preselected artery achieved in step (A); and

(D) determining a stress communicated to the sensor at said monitoring portion, said stress being caused by arterial pulsations; whereby the arterial blood pressure is determined based on said stress communicated to the sensor.

2. The method of claim 1, wherein step (A) is performed by the substeps of:

palpating the tissue adjacent the preselected artery to thereby approximate the location of the artery relative to the patient's anatomy; and

placing a mounting apparatus on the patient proximate said location of the artery, said mounting apparatus being adapted to maintain the sensor in a relatively fixed position relative to the patient's anatomy.

3. The method of claim 1, wherein step (A) is performed by the substeps of

removably securing a mounting apparatus to a preselected portion of the patient's anatomy that includes the preselected artery and surrounding tissue;

compressing the surrounding tissue using the sensor;

determining a set of stress contour data within the surrounding tissue caused by arterial pulsations within the artery; and

determining the location of the preselected artery relative to the sensor, using said set of stress contour data.

4. The method of claim 1, wherein step (B) is performed by the substep of moving the sensor such that the sensor bears against the tissue adjacent the artery until the pressure exerted upon the tissue and the arterial wall is sufficient to flatten at least a predetermined portion of the arterial wall.

5. The method of claim 1, wherein step (B) is performed by the substeps of determining optimum arterial compression by determining the stress in the tissue adjacent the preselected artery.

6. The method of claim 5, wherein step (B) is performed by the further substeps of:

varyingly compressing the preselected artery using the sensor to thereby applanate the preselected artery through a plurality of applanation stages, and at each said applanation stage;

determining a set of stress data indicative of stress communicated to a preselected portion of the sensor from the tissue adjacent the preselected artery, and for each said applanation stage,

selecting and computing an applanation optimization para meter, using said set of stress data, wherein the optimization parameter is selected from the group of parameters comprising a pulse parameter, distribution breadth parameter, pulse spread parameter, spatially averaged stress parameter, stress spatial curvature parameter, stress variation parameter;

determining an applanation state parameter;

determining a relationship between the selected applanation optimization parameter and the applanation state parameter; and

determining a value associated with a characteristic feature of said selected applanation optimization parameter relative to said artery applanation state parameter, said characteristic feature being indicative of said optimum arterial compression; whereby the optimum arterial compression is determined to be that degree of arterial applanation which produces the applanation optimization parameter value.

7. The method of claim 1, wherein step (B) is performed by the substeps of determining an off-optimum applanation state and applanating the preselected artery at said off-optimum applanation state.

8. The method of claim 7, wherein step (B) is performed by the further substeps of:

determining a first set of stress data, using the sensor, said first set of stress data being indicative of stress communicated to the sensor from the tissue adjacent the preselected artery;

determining which datum from said first set of stress data corresponds to an optimum artery applanation state;

applanating the preselected artery, using the sensor, at said off-optimum applanation state; and

determining a second set of stress data, using the sensor, said second set of data being indicative of stress communicated to the sensor from the tissue adjacent the preselected artery while the artery is in said off-optimum applanation state.

9. The method of claim 8 wherein step (D) is performed by the substeps of

determining a set of correction data, using said first and second sets of stress data; and

combining said second set of stress data with said set of correction data to thereby determine corrected stress data used to estimate the arterial blood pressure.

10. The method of claim 1, further comprising the step of calibrating the sensor.

11. The method of claim 10, wherein said calibrating is performed by the substeps of

heating a stress sensitive portion of the sensor;

displacing the stress sensitive portion of the sensor;

determining a response of the stress sensitive portion of the sensor to said heating and displacing; and

generating a set of calibration data for calibrating an output signal generated by the sensor; whereby the effects of temperature on the output of the sensor are eliminated.

12. The method of claim 1, wherein step (C) is performed by the substeps of:

orienting the sensor relative to the tissue adjacent th