Method and apparatus for non-invasively measuring hemodynamic parameters using parametrics
First Claim
1. A method of tonometrically measuring the pressure in the blood vessel of a living subject, comprising:
- providing a transducer adapted for determining the pressure applied to at least one surface thereof;
disposing said at least one surface of said transducer proximate to said blood vessel;
varying the level of compression applied to said blood vessel by said transducer over time;
determining the level of compression where a desired condition of the pulse pressure associated with said blood vessel exists based on the pressure determined by said transducer;
maintaining said transducer at or near said level of compression where said desired condition exists;
measuring at least one pressure value using said transducer during at least a portion of said act of maintaining; and
scaling said at least one pressure value based on at least the body mass index (BMI) of said subject to produce a corrected value said corrected value being substantially representative of the actual pressure within said blood vessel.
9 Assignments
0 Petitions
Accused Products
Abstract
An improved method and apparatus for non-invasively assessing one or more hemodynamic parameters associated with the circulatory system of a living organism. In one aspect, the invention comprises a method of measuring a hemodynamic parameter (e.g., arterial blood pressure) by applanating or compressing portions of tissue proximate to the blood vessel of concern until a desired condition is achieved, and then measuring the hemodynamic parameter. Such applanation effectively mitigates transfer and other losses created by the tissue proximate to the blood vessel, thereby facilitating accurate and robust tonometric measurement. An algorithm adapted to maintain optimal levels of applanation is also described. Methods and apparatus for scaling such hemodynamic parameter measurements based on subject physiology, and providing treatment to the subject based on the measured parameters, are also disclosed.
185 Citations
43 Claims
-
1. A method of tonometrically measuring the pressure in the blood vessel of a living subject, comprising:
-
providing a transducer adapted for determining the pressure applied to at least one surface thereof;
disposing said at least one surface of said transducer proximate to said blood vessel;
varying the level of compression applied to said blood vessel by said transducer over time;
determining the level of compression where a desired condition of the pulse pressure associated with said blood vessel exists based on the pressure determined by said transducer;
maintaining said transducer at or near said level of compression where said desired condition exists;
measuring at least one pressure value using said transducer during at least a portion of said act of maintaining; and
scaling said at least one pressure value based on at least the body mass index (BMI) of said subject to produce a corrected value said corrected value being substantially representative of the actual pressure within said blood vessel.
-
-
2. A method of measuring the pressure in the blood vessel of a living subject, comprising:
-
providing at least one transducer adapted for determining the pressure applied to at least one surface thereof;
disposing said at least one surface of said at least one transducer proximate to said blood vessel;
varying the level of compression applied to said blood vessel by said at least one transducer over time;
determining the level of compression where a desired condition of the pulse pressure associated with said blood vessel exists based on the pressure determined by said at least one transducer;
maintaining said at least one transducer at or near said level of compression where said desired condition exists; and
measuring at least one pressure value using said transducer during at least a portion of said act of maintaining. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
measuring at least one pressure waveform during said act of performing; and
identifying at least one artifact within said at least one waveform, said at least one artifact being associated with said desired condition.
-
-
8. The method of claim 7, wherein said act of identifying at least one artifact comprises:
-
analyzing said at least one waveform on a per-beat basis;
evaluating at least one parameter associated with a first beat of said at least one waveform;
evaluating said at least one parameter associated with at least one other beat of said at least one waveform; and
applying at least one criterion to said beats to identify said desired condition of pulse pressure.
-
-
9. The method of claim 8, wherein said at least one parameter comprises the pressure amplitude, and said desired condition comprises maximum pulse pressure.
-
10. The method of claim 9, wherein said at least one other beat comprises two consecutive beats, said two consecutive beats being sequential with said first beat, said criterion comprising a difference in the pressure amplitude of a predetermined percentage.
-
11. The method of claim 2, further comprising:
-
determining a first physiologic parameter of said subject;
determining a second physiologic parameter of said subject;
forming a relationship between said first and second parameters; and
using said relationship to scale said at least one pressure value.
-
-
12. The method of claim 11, wherein said first physiologic parameter comprises the body mass index (BMI) of said subject.
-
13. The method of claim 12, wherein said second physiologic parameter comprises the pulse pressure measured from said subject.
-
14. The method of claim 13, wherein said act of forming comprises forming a ratio of said BMI to said PP.
-
15. The method of claim 14, wherein said act of using comprises (i) correlating said ratio to a scale factor;
- and (ii) multiplying said at least one pressure value by said scale factor.
-
16. The method of claim 12, wherein said second physiologic parameter comprises the circumference of said subject'"'"'s wrist (WC).
-
17. The method of claim 16, wherein said act of forming comprises forming a ratio of said BMI to said WC.
-
18. The method of claim 2, wherein said act of varying the level of compression over time comprises varying the level of compression at a rate which is at least in part a function of the heart rate of said subject.
-
19. The method of claim 2, further comprising:
-
determining at least one physiologic parameter of said subject;
identifying a relationship between said at least one parameter and a scaling factor for said at least one pressure value measured from said blood vessel; and
using said scaling factor to scale said at least one pressure value.
-
-
20. The method of claim 19, wherein said at least one parameter comprises body fat content.
-
21. The method of claim 19, further comprising determining a mean pressure within said at least one waveform;
- and
wherein said act of using said scaling factor to scale said at least one pressure value comprises applying said scaling factor to pressure values above and below said mean.
- and
-
22. The method of claim 21, wherein said act of applying scaling factors to pressure values above and below said mean comprises applying a positive (+) scaling factor to systolic pressures above said mean, and a negative (−
- ) scaling factor to diastolic pressures below said mean.
-
23. The method of claim 2, further comprising varying the position of said at least one transducer in a substantially lateral direction relative to said blood vessel so as to optimize said desired condition of said act of determining.
-
24. The method of claim 23, further comprising varying the position of said at least one transducer in a substantially proximal direction relative to said blood vessel so as to optimize said desired condition of said act of determining.
-
25. The method of claim 24, wherein said desired condition comprises maximum pulse pressure, and at least one of said acts of varying comprises:
-
measuring at least one pressure waveform during said act of varying;
varying the position of said at least one transducer over a range of positions; and
identifying that position where said pulse pressure is maximized for a given level of compression.
-
-
26. An apparatus for measuring the pressure within the blood vessel of a living subject comprising:
-
a pressure transducer adapted to detect the pressure associated with said blood vessel and generate a signal relating thereto;
at least one storage device associated with said pressure transducer, said at least one storage device having scaling data stored therein;
at least one applanation assembly adapted to bias a portion of tissue proximate to said blood vessel;
a controller operatively coupled to said at least one applanation assembly and adapted to control the position thereof; and
a processor operatively connected to said transducer, at least one storage device, and said controller, said processor configured to generate an estimate of said blood pressure within said vessel based at least in part on said signal and said scaling data. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
-
-
43. An information storage device, comprising:
-
a data storage medium;
a plurality of data stored on said medium, said plurality of data comprising a computer program adapted to run on a data processor, said data processor being operatively coupled to a controller which controls the position of a pressure transducer, said computer program, processor and controller being configured for determining the blood pressure of a living subject using the method comprising;
varying the level of compression applied to said blood vessel by at least one pressure transducer over time;
determining the level of compression where a desired condition of the pulse pressure associated with said blood vessel exists based on the pressure determined by said at least one transducer;
maintaining said at least one transducer at or near said level of compression where said desired condition exists; and
measuring at least one pressure value using said transducer during at least a portion of said act of maintaining.
-
Specification