Method and apparatus for calculating blood pressure of an artery

• US 6,589,185 B1
• Filed: 06/14/2000
• Issued: 07/08/2003
• Est. Priority Date: 11/09/1993
• Status: Expired due to Fees

• Current Assignee: Medwave, Inc.
• Original Assignee: Medwave, Inc.
• Inventors: Curran, Timothy G., Poliac, Marius O., Archibald, G. Kent, Danielson, Orland H., Thede, Roger C.
• Primary Examiner(s): Gilbert, Samuel G.
• Application Number:
  US09/594,051
• Time in Patent Office: 1,119 Days
• Field of Search: 600/490-496, 600/500-503
• US Class Current: 600/494
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02116 of pulse wave amplitude A61B5/02225 takes precedence
• CPC Class Codes: A61B 5/02141 Details of apparatus construction, e.g. pump units or housings therefor, cuff pressurising systems, arrangements of fluid conduits or circuits A61B5/02233, A61B5/0235 take precedence
• CPC Class Codes: A61B 5/02225 using the oscillometric method
• CPC Class Codes: A61B 5/02233 Occluders specially adapted therefor tourniquets A61B17/132
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure

Abstract

The present invention is a method for calculating blood pressure of an artery having a pulse. The method includes applying a varying pressure to the artery. Pressure waveforms are sensed to produce pressure waveform data. Waveform parameters are derived from the sensed pressure waveform data. Blood pressure is then determined using the derived parameters.

Claims

1. A method for determining blood pressure of an artery having a pulse, the method comprising:

applying a pressure to the artery;

sensing pressure produced by the artery to produce sensed pressure data representing a pressure waveform for at least one pulse;

deriving a plurality of parameters related to waveform shape from the sensed pressure data including at least one of the following;

(a) rise time of a selected portion of a waveform, (b) applied pressure corresponding to a starting point of a waveform, (c) applied pressure corresponding to an ending point of a waveform, (d) pressure of a waveform at a selected time, (e) a pressure corresponding to a selected point on a waveform, (f) a time value corresponding to a width of a selected portion of a waveform, (g) mean amplitude of a waveform, (h) mean of a curve generated from data taken from a plurality of waveforms; and

determining a blood pressure value based upon the parameters.

2. The method of claim 1 including:

selecting a set of data representing a pressure waveform which exhibited a maximum amplitude, wherein at least one of the plurality of parameters is derived from the selected set of data.

3. A non-invasive blood pressure monitoring device, the monitoring device comprising:

pressure means for applying pressure to the artery so that the artery exhibits pressure data;

sensing means for sensing the pressure data;

signal producing means connected to the sensing means for producing output signals corresponding to the sensed pressure data; and

processing means for receiving the output signals from the signal producing means, for deriving a plurality of parameters related to waveform shape using sensed pressures including at least one parameter other than maximum pressure waveform amplitude and for determining a blood pressure value using the derived parameters.

4. The blood pressure monitoring device of claim 3 herein the sensing means includes:

a transducer;

sensor support;

a flexible diaphragm coupled to the sensor support and having an active portion for transmitting blood pressure pulses of the underlying artery; and

a fluid coupling medium coupled between the flexible diaphragm and the transducer for transmitting blood pressure pulses within the underlying artery from the flexible diaphragm to the transducer.

5. The blood pressure monitoring device of claim 3 wherein the signal producing means includes:

an input signal processor for processing data received from the sensing means and for filtering noise; and

an analog-to-digital converter for converting the signal from the input signal processor into digital form representing pressure of the sensed blood pressure pulses.

6. A method for determining blood pressure of an artery having a pulse, the method comprising:

sensing pressure data representing pressure waveforms for each of a plurality of pulses produced by the artery while applying a sweeping increasing pressure to the artery;

deriving parameters related to waveform shape from the sensed pressure data; and

determining a blood pressure value based upon the parameters.

7. A method for determining blood pressure of an artery having a pulse, the method comprising:

sensing pressure data produced by the artery during a plurality of pulses while applying an increasing pressure to the artery, the pressure data representing a pressure waveform for each pulse;

deriving a plurality of parameters related to waveform shape of at least one pressure waveform including at least one parameter other than maximum pressure waveform amplitude from the sensed pressure data; and

determining a blood pressure value based upon the parameters.

8. A method for determining blood pressure of an artery having a pulse, the method comprising:

applying a pressure to the artery;

sensing pressure data produced by the artery representing a pressure waveform for at least one pulse;

deriving a plurality of waveform shape parameters from the sensed pressure data; and

determining a blood pressure value based upon the plurality of waveform shape parameters and a stored set of coefficients.

9. The method of claim 8 including:

selecting a set of data from a plurality of beats, wherein at least one parameter is derived from the selected set of data.

10. A non-invasive blood pressure monitoring device, the monitoring device comprising:

pressure means for applying a pressure to the artery so that the artery exhibits pressure data representing a pressure waveform for at least one pulse;

sensing means for sensing the pressure data;

signal producing means connected to the sensing means for producing output signals corresponding to the sensed pressure data;

storing means for storing a set of coefficients; and

processing means for receiving the output signals from the signal producing means, for deriving a plurality of waveform shape parameters using sensed pressures and for determining a blood pressure value using the derived parameters and the stored set of coefficients.

11. A non-invasive blood pressure monitoring device, the monitoring device comprising:

pressure means for applying a pressure to the artery so that the artery exhibits pressure data representing a pressure waveform for at least one pulse;

sensing means for sensing the pressure data;

signal producing means connected to the sensing means for producing output signals corresponding to the sensed pressure data; and

processing means for receiving the output signals from the signal producing means, for deriving a plurality of parameters related to waveform shape including at least one of the following;

(a) rise time of a selected portion of a waveform, (b) applied pressure corresponding to a starting point of a waveform, (c) applied pressure corresponding to an ending point of a waveform, (d) pressure of a waveform at a selected time, (e) a pressure corresponding to a selected point on a waveform, (f) a time value corresponding to a width of a selected portion of a waveform, (g) mean amplitude of a waveform, (h) mean of a curve generated from data taken from a plurality of waveforms.

12. A method for monitoring blood pressure data produced by an artery, the method comprising:

sensing pressure data produced by the artery over time representing a plurality of arterial pressure waveforms;

determining a maximum pressure amplitude for each of the plurality of arterial pressure waveforms from the sensed pressure data;

applying an increasing pressure to the artery until at least one waveform has a maximum pressure amplitude less than a maximum pressure amplitude of a preceding waveform; and

determining a blood pressure value based upon shape of a least one of the pressure waveforms.

13. A method for determining blood pressure of an artery, the method comprising:

positioning a sensor having a constant volume fluid filled sensing chamber over the artery;

applying force to the sensor to press the sensor towards the artery;

sensing pressure data produced by the artery by sensing pressure within the constant volume fluid filled chamber to generate pressure waveform data;

deriving waveform shape parameters from the pressure data; and

determining a blood pressure value based upon the waveform shape parameters.

14. The method of claim 13 wherein the step of applying varying force to the sensor includes:

applying an increasing force to the sensor.

15. The method of claim 13 wherein the step of applying a varying pressure to the sensor includes:

sweeping the force being applied to the sensor.

16. The method of claim 15 wherein the step of applying a varying force to the sensor includes:

intermittently varying the force applied to the artery.

17. A non-invasive blood pressure measurement system comprising:

a sensor having a constant volume fluid filled sensing chamber configured for being positioned over an underlying artery;

force applying means for applying a force to the sensor to press the sensor against the underlying artery;

sensing means for sensing pressure within the constant volume fluid filled sensing chamber representing pressure data produced by the underlying artery;

signal producing means connected to the sensing means for producing output signals corresponding to the sensed pressures within the constant volume fluid filled sensing chamber;

storing means for storing a set of coefficients; and

processing means for receiving the output signals from the signal producing means, for deriving a plurality of waveform shape parameters using the sensed pressures and for determining a blood pressure value using the derived parameters and the stored set of coefficients.

18. The device of claim 17 including:

means for sensing the force applied to the sensor.

19. A non-invasive blood pressure measurement system comprising:

a sensor having a constant volume fluid filled sensing chamber configured for being positioned over an underlying artery;

means for applying force to the sensor to press the sensor against the underlying artery;

sensing means for sensing pressure within the constant volume fluid filled sensing chamber during a plurality of pulses in the underlying artery; and

means for deriving a blood pressure value based upon a waveform shape analysis of the sensed pressure representing at least one pressure waveform produced by one of the pulses.