Method and instrument to measure vascular impedance

• US 20020028998A1
• Filed: 09/17/2001
• Published: 03/07/2002
• Est. Priority Date: 12/28/1990
• Status: Active Grant

• Current Assignee: Hypertension Diagnostics, Inc.
• Original Assignee: Hypertension Diagnostics, Inc.
• Inventors: Cohn, Jay N., Finkelstein, Stanley M., Chesney, Charles F.
• Granted Patent: US 6,623,434 B2
• Time in Patent Office: Days
• US Class Current: 600/483
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: G09B 23/28 for medicine
• CPC Class Codes: Y10S 128/92 Computer assisted medical diagnostics

Abstract

A vascular impedance measurement instrument includes a transducer to obtain a digitized arterial blood pressure waveform. The digitized data is used to determine cardiac output, and to subsequently obtain measurements of impedance parameters using the modified Windkessel model of the arterial system. The instrument is used as an aid in diagnosing, treating and monitoring patients with cardiovascular disease.

Claims

1. A vascular impedance measurement instrument, comprising:

means for measuring the arterial pressure and producing a corresponding series of digitized data samples representing the waveform of the arterial blood pressure of a patient;

means for determining the mean arterial pressure of the patient from said sample series;

means for determining a cardiac output measurement value for the patient from said sample series and from clinically derived patient data;

means for determining for the patient one or more of the parameters of a vascular impedance model from said sample series and from said cardiac output value; and

means for displaying or reporting said one or more values.

2. An instrument according to claim 1 further wherein said means for determining a cardiac output measurement includes means for determining the measurement using the ejection time of the heart as determined from said sample series and from the heart rate, body surface area and age of the patient.

3. The instrument of claim 2 further wherein said means for determining includes means for determining stroke volume substantially in accordance with the following formula;

SV=−

6.6+(0.25×

ET)+(40.4×

BSA)−

(0.51×

Age)−

(0.62×

HR),

where SV equals stroke volume in ml/beat, ET is ejection time in msec, BSA is body surface area in square meters, Age is expressed in years, and HR is heart rate in beats per minute;

and wherein cardiac output is calculated from stroke volume.

4. The instrument of claim 1 further wherein the means for measuring includes a transducer for converting the analog arterial waveform to a corresponding electrical signal.

5. The instrument of claim 4 wherein said means for measuring includes means for digitizing said electrical signal to produce said digitized samples.

6. The instrument of claim 1 further wherein said vascular impedance model is the modified Windkessel model of the vasculature.

13. The instrument of claim 1 further wherein said vascular impedance model is a first order model of the vasculature.

17. The instrument of claim 1 wherein said means for measuring measures the arterial waveform noninvasively.

7. A vascular impedance measurement instrument, comprising:

means for noninvasively measuring the arterial pressure and producing a corresponding series of digitized data samples representing the waveform of the arterial blood pressure of a patient;

means for determining the mean arterial pressure of the patient from said sample series;

means for determining a cardiac output measurement value for the patient from said sample series and from clinically derived patient data;

means for determining for the patient one or more of the parameters of a vascular impedance model from said sample series and from said cardiac output value; and

means for displaying or reporting said one or more values.

8. An instrument according to claim 7 further wherein said means for determining a cardiac output measurement includes means for determining the measurement using the ejection time of the heart as determined from said sample series and from the heart rate, body surface area and age of the patient.

9. The instrument of claim 8 further wherein said means for determining includes means for determining stroke volume substantially in accordance with the following formula:

SV=−

6.6+(0.25×

ET)+(40.4×

BSA)−

(0.51×

Age)−

(0.62×

HR),

where SV equals stroke volume in ml/beat, ET is ejection time in msec, BSA is body surface area in square meters, Age is expressed in years, and HR is heart rate in beats per minute;

and wherein cardiac output is calculated from stroke volume.

10. The instrument of claim 7 further wherein the means for measuring includes a transducer for converting the analog arterial waveform to a corresponding electrical signal.

11. The instrument of claim 10 wherein said means for measuring includes means for digitizing said electrical signal to produce said digitized samples.

12. The instrument of claim 7 further wherein said vascular impedance model is the modified Windkessel model of the vasculature.

14. The instrument of claim 7 further wherein said vascular impedance model is a first order model of the vasculature.

15. The instrument of claim 7 further wherein said means for measuring includes a transducer unit for noninvasively measuring the blood pressure waveform.

16. The instrument of claim 15 wherein said transducer unit measures the blood pressure waveform using a noninvasive blood pressure monitor.