Method and apparatus for control of non-invasive parameter measurements

• US 20040059234A1
• Filed: 03/20/2003
• Published: 03/25/2004
• Est. Priority Date: 08/01/2002
• Status: Active Grant

• Current Assignee: United States GTM Medical Devices
• Original Assignee: Tensys Medical Inc. (Recorders & Medicare Systems Pvt Ltd.)
• Inventors: Voss, Gregory I., Gallant, Stuart L., Martin, Gregory J., Craycroft, Warren, Goharlaee, Manouchehr
• Granted Patent: US 7,291,112 B2
• Time in Patent Office: Days
• US Class Current: 600/500
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/684 Indicating the position of the sensor on the body
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00

Abstract

Improved methods and apparatus for non-invasively assessing one or more parameters associated with fluidic systems such as the circulatory system of a living organism, when such parameters are potentially affected by other concurrent events. In one exemplary embodiment, apparatus and methods for compensating for occlusive events (e.g., pressure cuff inflation) occurring ipsilateral to the location of parameter measurement are disclosed. Upon passive detection of signal degradation resulting from the event, the apparatus selectively enters a “wait state” wherein further processing of the hemodynamic data is suspended until the degrading event subsides. This behavior mitigates any adverse effects the event might have on the accuracy of the representation of the measured hemodynamic parameter generated by the system. In another exemplary embodiment, the measured data is analyzed in order to classify the type of event (e.g., occlusive or other), such classification allowing the system to appropriately tailor its response to the event.

Claims

1. A method of measuring blood pressure in a living subject, comprising:

measuring pressure from a blood vessel at a first location on said subject;

at least partly occluding a blood vessel at a second location on said subject, said act of occluding having at least some effect on said act of measuring; and

adjusting said act of measuring based at least in part on said effect.

2. The method of claim 1, wherein said act of measuring comprises measuring pressure tonometrically from an artery, said second location being ipsilateral thereto.

3. The method of claim 2, wherein said act of at least partly occluding comprises at least partly occluding said blood vessel using an inflatable cuff.

4. The method of claim 1, wherein said act of adjusting comprises ceasing ongoing adjustment of applanation pressure to said first location for at least a first period.

5. The method of claim 4, wherein said act of adjusting applanation pressure comprises varying the pressure applied to the surface of the skin overlying the blood vessel at said first location by a pressure sensor.

6. The method of claim 1, wherein said act of adjusting comprises:

identifying a lack of useful pressure data obtained from said act of measuring; and

delaying subsequent corrective measures for reacquiring useful data for at least a first period.

7. A method of mitigating the effects of a blood vessel occlusion on a blood pressure measurement, comprising:

passively determining a change in at least one parameter associated with data generated from said measurement of blood pressure; and

adjusting processing of said data based on said determining, said adjusting at least in part mitigating said effects.

8. The method of claim 7, wherein said act of passively determining a change comprises:

detecting the absence of one or more cardiac beats in said data; and

detecting a reduction in the magnitude of the pulse pressure.

9. Blood pressure measuring apparatus, comprising:

a non-invasive pressure sensor adapted for sensing the pressure applied thereto by a blood vessel at a first location on the body of a subject and generating a signal relating thereto;

a processor operatively coupled to said sensor; and

a computer program running on said processor, said computer program adapted to process said signal to produce a representation of said blood pressure;

wherein said computer program is further adapted to;

(i) detect a loss of pressure event within said signal; and

(ii) adjust said processing based on said event.

10. The apparatus of claim 9, further comprising an applanation mechanism coupled to said pressure sensor, wherein said sensor and mechanism cooperate to selectively compress said blood vessel during said act of sensing.

11. The apparatus of claim 10, wherein said adjustment of said act of processing comprises delaying processing of said signal until said loss of pressure event has terminated.

12. The apparatus of claim 10, wherein said computer program further comprises:

a beat detector; and

a no-beat process;

wherein said beat detector advises said no-beat process as to detected beats within said signal, said no beat process suspending said act of processing if no beats are detected within a first time interval.

13. The Apparatus of claim 10, wherein said computer program is further adapted to modulate the level of compression applied to said blood vessel via said mechanism, said act of processing further comprising correcting the sensed pressure.

14. A method of processing pressure data obtained from a pressure sensor applied to a living subject, comprising:

analyzing said data to derive a substantially continuous representation of said pressure;

detecting a loss of pressure event within said signal; and

adjusting said analyzing based on said event.

15. The method of claim 14, wherein said pressure data is obtained tonometrically from said subject, and said act of adjusting comprises:

suspending said act of analyzing for a predetermined period;

after expiration of said period, determining whether said event has terminated; and

if said event has terminated, re-initiating said act of analyzing.

16. The method of claim 15, wherein said act of adjusting further comprises suspending changing a level of compression applied to said subject during said tonometric obtaining of said data during said period.

17. The method of claim 14, wherein said pressure data is obtained tonometrically from said subject, and said act of detecting comprises detecting a reduction in the difference between systolic and diastolic pressures present in said data.

18. Blood pressure measurement apparatus adapted to tonometrically measure blood pressure at a first location, passively detect an occlusive event occurring at a location ipsilateral to said first location, and compensate for the effects of said occlusive event on said measuring.

19. Blood pressure measurement apparatus adapted to tonometrically measure blood pressure form a blood vessel disposed at a first location, comprising:

a pressure sensor adapted to sense pressure and generate signals relating thereto;

a processor operatively coupled to said sensor, including a computer program running thereon, said processor and program cooperating to process said signals to generate a representation of said blood pressure; and

applanation apparatus coupled to said pressure sensor and operatively controlled at least in part by said processor and said computer program, said applanation apparatus adapted to variably compress said blood vessel;

wherein said processing of said signals comprises;

(i) passively detecting an occlusive event occurring at a location ipsilateral to said first location;

(ii) suspending movement of said applanation apparatus for at least a first period; and

(iii) waiting for at least said first period until the effects of said occlusive event on said signals has substantially subsided.

20. A method of processing blood pressure data, comprising:

obtaining a first plurality of data corresponding to a first state of operation;

obtaining a second plurality of data corresponding to a second state of operation;

evaluating said first and second data; and

based on said act of evaluating, selectively adjusting the subsequent processing of said blood pressure data.

21. The method of claim 20, wherein said act of obtaining first data corresponding to a first state comprises obtaining pressure data during a normal (non-event) state of operation, and said act of obtaining second data corresponding to a second state comprises obtaining pressure data during an event which results in at least partial degradation of said pressure data.

22. The method of claim 21, wherein said act of evaluating at least one metric comprises evaluating at least one metric associated with said first and second pluralities of data.

23. The method of claim 22, further comprising entering a wait state based at least in part on said second plurality of data.

24. The method of claim 23, wherein said act of selectively adjusting comprises either:

(i) exiting said wait state, or (ii) continuing operating in said wait state for a period of time, based on said evaluation of said metric.

25. Apparatus adapted to generate a representation of the blood pressure the blood vessel of a living subject, said generating comprising:

tonometrically sensing pressure at a first location using at least one sensor and generating signals relating thereto;

passively detecting a degradation of said signals;

classifying said degradation based at least in part on said signals; and

compensating for the effects of said degradation on said representation.

26. The apparatus of claim 25, wherein said classifying comprises at least determining whether said degradation is the result of an occlusive event occurring ipsilateral to said first location.

27. The apparatus of claim 26, wherein said compensating comprises entering a wait state, the duration of said wait state being substantially related to the estimated duration of said occlusive event.

28. Hemodynamic data processing apparatus, comprising:

a processor adapted to receive a plurality of hemodynamic data and process same;

a first data storage location adapted to receive at least a first portion of said plurality of hemodynamic data;

a second data storage location adapted to receive at least a second portion of said plurality of hemodynamic data; and

a computer program running on said processor, said program adapted to;

segregate said plurality of data into said first and second portions for storing in said first-and second locations, respectively;

evaluate said first and second portions based on at least one metric; and

based at least in part on said evaluation, control said segregation of subsequent hemodynamic data received by said processor.

29. A method of continuously and non-invasively measuring blood pressure in a living subject, comprising:

tonometrically measuring pressure from a blood vessel at a first location on said subject using at least one sensor, said act of measuring further comprising controllably applanating said blood vessel using said at least one sensor;

at least partly occluding a blood vessel at a second location on said subject, said second location being ipsilateral to said first location, said act of occluding having at least some effect on said act of measuring;

detecting, based at least in part on said effect, that said act of at least partly occluding is occurring; and

adjusting said act of measuring in order to mitigate said effect.

30. A method of measuring blood pressure in a living subject, comprising:

a step for determining at least one hemodynamic parameter from a blood vessel of said subject;

a step for ipsilaterally affecting said determination of said hemodynamic parameter; and

a step for adjusting said act of determining based at least in part on said affecting.

31. A method of assessing a living subject, comprising:

measuring pressure from a blood vessel at a first location on said subject;

measuring blood pressure from a blood vessel at a second location, said measuring at said second location having an effect on said measuring at said first location;

detecting said effect; and

adjusting said act of measuring at said first location based at least in part on said detecting.