Apparatus and method for non-invasively monitoring a subjects arterial blood pressure

• US 6,228,034 B1
• Filed: 07/20/1998
• Issued: 05/08/2001
• Est. Priority Date: 07/20/1998
• Status: Expired due to Term

• Current Assignee: Tensys Medical Inc. (Recorders & Medicare Systems Pvt Ltd.)
• Original Assignee: Tensys Medical Inc. (Recorders & Medicare Systems Pvt Ltd.)
• Inventors: O'Leary, Stephen H., Voss, Gregory I., Somerville, Alvis J.
• Primary Examiner(s): O'Connor, Cary
• Assistant Examiner(s): CARTER, RYAN CHRISTOPHER
• Application Number:
  US09/120,069
• Time in Patent Office: 1,023 Days
• Field of Search: 600/485, 600/500-503, 600/561
• US Class Current: 600/485
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers

Abstract

Apparatus is disclosed for non-invasively monitoring a subject'"'"'s blood pressure, in which a pressure sensor assembly that includes a pressure transducer is compressed against tissue overlying an artery, with sufficient force to compress the artery. A motor first servo control system optimizes the amount of artery compression, which occurs at a mean transmural pressure of about zero, by modulating one side of a lever arm compressing the assembly against the tissue, creating a pressure signal indicative of transmural pressure. Since different pressure effects are realized according to the amount of artery compression, an appropriate control signal can be produced that provides for a second motor to adjust the other side of the lever arm to provide the optimum compression of the assembly into the tissue overlying the artery. The apparatus is optimally positioned over an artery by including an ultrasonic blood flow sensor configured to sense the flow of blood under the pressure transducer.

Claims

1. An apparatus for monitoring the pressure within a subject'"'"'s blood vessel, comprising:

a pressure sensor assembly that produces a pressure signal indicative of the pressure applied against it;

a coupling device configured to urge the pressure sensor assembly into compressive engagement with tissue overlying a subject'"'"'s blood vessel, to compress the vessel such that pressure variations within the vessel are coupled through the tissue to the pressure sensor assembly; and

a controller configured to controllably vary the coupling device so as to vary the position of the pressure sensor assembly relative to the subject'"'"'s blood vessel;

wherein the coupling device comprises

a) a lever arm,

b) a first variable positioning device configured to controllably adjust a nominal location of the pressure transducer by actuating a first portion of the lever arm, and

c) a second variable positioning device configured to modulate the pressure sensor assembly, about the nominal location, by actuating a second portion of the lever arm, the second portion of the lever arm being different from the first portion of the lever arm;

wherein the controller is configured to controllably vary the second variable positioning device so as to modulate the pressure sensor assembly;

wherein the controller is configured to monitor the effect of the pressure sensor assembly'"'"'s modulation on the pressure signal;

wherein the controller is configured to produce an error signal indicative of adjustments to the pressure sensor assembly'"'"'s position which will cause the blood vessel to be compressed according to a prescribed requirement; and

wherein the controller is configured to controllably vary the first variable positioning device according to the error signal to controllably position the pressure sensor assembly to cause the subject'"'"'s blood vessel to be compressed according to the prescribed requirement.

2. The apparatus for monitoring the pressure within a subject'"'"'s blood vessel of claim 1, wherein the prescribed requirement is a prescribed mean amount.

3. The apparatus for monitoring the pressure within a subject'"'"'s blood vessel of claim 1, wherein the second variable positioning device includes a second motor configured to rotate an eccentric cam within a slot in the lever arm.

4. The apparatus for monitoring the pressure within a subject'"'"'s blood vessel of claim 1, wherein the first variable positioning device includes a first motor configured to rotate an eccentric cam within a slot in the lever arm.

5. An apparatus for monitoring the pressure within a subject'"'"'s blood vessel, comprising:

a pressure transducer that produces a pressure signal indicative of the pressure applied against it;

a coupling device comprising;

a base configured to provide reaction forces for urging the pressure transducer into compressive association with the tissue overlying the subject'"'"'s blood vessel, thereby compressing the vessel such that the pressure variations within the vessel are coupled through the tissue to the pressure transducer;

a first variable positioning device configured to controllably adjust the nominal location toward the target location;

a second variable positioning device configured to modulate the pressure transducer toward and away from the subject'"'"'s blood vessel, about the nominal location; and

a lever arm connected to the pressure transducer;

wherein the first variable positioning device is configured to controllably adjust the nominal location relative to the target location by actuating a first portion of the lever arm, and the second variable positioning device is configured to modulate the pressure transducer by actuating a second portion of the lever arm, the second portion of the lever arm being different from the first portion of the lever arm; and

a controller configured to control the coupling device so as to controllably modulate the pressure transducer toward and away from the subject'"'"'s blood vessel, about a nominal location;

wherein the controller is configured to monitor the effect of the modulation on the pressure signal and to produce an error signal indicative of the deviation of the nominal location from a target location at which the vessel is compressed according to a prescribed requirement, and controllably adjust the nominal location toward the target location using the coupling device.

6. The apparatus for monitoring the pressure within a subject'"'"'s blood vessel of claim 5, wherein the pressure transducer is connected to the lever arm at a third portion of the lever arm, the third portion of the lever arm being between the first portion and the second portion of the lever arm.

7. An apparatus for monitoring the pressure within a subject'"'"'s blood vessel, comprising:

a pressure transducer that produces a pressure signal indicative of the pressure applied against it;

a coupling device comprising;

a base configured to provide reaction forces for urging the pressure transducer into compressive association with the tissue overlying the subject'"'"'s blood vessel, thereby compressing the vessel such that the pressure variations within the vessel are coupled through the tissue to the pressure transducer;

a first variable positioning device configured to controllably adjust the nominal location toward the target location; and

a second variable positioning device configured to modulate the pressure transducer toward and away from the subject'"'"'s blood vessel, about the nominal location;

wherein the first and second variable positioning devices and the pressure transducer are configured to be removable from the base by way of a quick-release attachment; and

a controller configured to control the coupling device so as to controllably modulate the pressure transducer toward and away from the subject'"'"'s blood vessel, about a nominal location;

wherein the controller is configured to monitor the effect of the modulation on the pressure signal and to produce an error signal indicative of the deviation of the nominal location from a target location at which the vessel is compressed according to a prescribed requirement, and controllably adjust the nominal location toward the target location using the coupling device.

8. An apparatus for monitoring the pressure within a subject'"'"'s blood vessel, comprising:

a pressure transducer that produces a pressure signal indicative of the pressure applied against it;

a coupling device configured to urge the pressure transducer into compressive association with tissue overlying a subject'"'"'s blood vessel, to compress the vessel such that the pressure variations within the vessel are coupled through the tissue to the pressure transducer;

a sensor housing connected to the coupling device, the sensor housing defining a chamber;

a plug disposed at least partly within the sensor housing'"'"'s chamber, wherein the sensor housing and the plug are configured such that the plug provides the compressive association between the pressure transducer and the tissue overlying the subject'"'"'s blood vessel; and

a controller configured to control the coupling device so as to controllably modulate the pressure transducer toward and away from the subject'"'"'s blood vessel, about a nominal location;

wherein the controller is configured to monitor the effect of the modulation on the pressure signal and to produce an error signal indicative of the deviation of the nominal location from a target location at which the vessel is compressed according to a prescribed requirement.

9. The apparatus for monitoring the pressure within a subject'"'"'s blood vessel of claim 8, wherein the plug is composed of a substantially incompressible, compliant material.

10. An apparatus for monitoring the pressure within a subject'"'"'s blood vessel comprising:

a pressure transducer that produces a pressure signal indicative of the pressure applied against it;

a sampler configured to periodically sample the pressure transducer'"'"'s pressure signal;

a processor configured to process the sampled pressure signal to produce a plurality of pressure waveforms, each waveform representing the blood vessel pressure at a compression level associated with a specific transmural pressure;

a coupling device configured to urge the pressure transducer into compressive association with tissue overlying a subject'"'"'s blood vessel, to compress the vessel such that the pressure variations within the vessel are coupled through the tissue to the pressure transducer; and

a controller configured to control the coupling device so as to controllably modulate the pressure transducer toward and away from the subject'"'"'s blood vessel, about a nominal location;

wherein the controller is configured to monitor the effect of the modulation on the pressure signal and to produce an error signal indicative of the deviation of the nominal location from a target location at which the vessel is compressed according to a prescribed requirement.

11. The apparatus for monitoring the pressure within a subject'"'"'s blood vessel of claim 10, wherein the sampler samples the pressure transducer'"'"'s pressure signal at a frequency that is a multiple of a frequency that is characteristic of the pressure transducer'"'"'s modulation.

12. The apparatus for monitoring the pressure within a subject'"'"'s blood vessel of claim 10, wherein the processor is further configured:

to select one of the plurality of pressure waveforms; and

to rank the selected waveform relative to the waveforms that were not selected, thereby providing for the controller to produce an error signal indicative of the deviation of the nominal location from the target location.

13. A method for monitoring the pressure within a subject'"'"'s blood vessel, comprising:

providing a pressure transducer configured to produce a signal indicating a pressure applied to the pressure transducer, the pressure transducer being connected to a lever arm having a first portion and a second portion;

locating the pressure transducer at a nominal location relative to the subject such that the pressure transducer is in compressive association with tissue overlying a subject'"'"'s blood vessel, thereby compressing the vessel such that the pressure variations within the vessel are coupled through the tissue to the pressure transducer;

modulating the pressure transducer toward and away from the subject'"'"'s blood vessel, about the nominal location, by oscillating the second portion of the lever arm, thereby varying the blood vessels transmural pressure and causing variations in the signal produced by the pressure transducer;

monitoring the effect of the pressure transducer'"'"'s modulation on the pressure signal;

producing an error signal indicative of the relative position of the nominal location from a target location such that the vessel would be compressed according to a prescribed requirement; and

adjusting the nominal location toward the target location in response to the error signal, the act of adjusting comprising changing the position of the first portion of the lever arm.

14. A method for monitoring the pressure within a subject'"'"'s blood vessel, comprising:

providing a pressure transducer configured to produce a signal indicating a pressure applied to the pressure transducer;

locating the pressure transducer at a nominal location relative to the subject such that the pressure transducer is in compressive association with tissue overlying a subject'"'"'s blood vessel, thereby compressing the vessel such that the pressure variations within the vessel are coupled through the tissue to the pressure transducer;

linearly oscillating the pressure transducer toward and away from the subject'"'"'s blood vessel, about the nominal location, to vary the blood vessel'"'"'s transmural pressure, and thereby cause variations in the signal produced by the pressure transducer;

monitoring the effect of the pressure transducer'"'"'s modulation on the pressure signal; and

producing an error signal indicative of the relative position of the nominal location from a target location such that the vessel would be compressed according to a prescribed requirement.