Method for determining diastolic arterial blood pressure in a subject

• US 4,718,428 A
• Filed: 01/22/1987
• Issued: 01/12/1988
• Est. Priority Date: 02/17/1984
• Status: Expired due to Fees

• Current Assignee: Cortronic Corporation
• Original Assignee: Cortronic Corporation
• Inventors: Russell, Ted W.
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/006,628
• Time in Patent Office: 355 Days
• Field of Search: 128/672, 128/677-686
• US Class Current: 600/492
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02156 Calibration means
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/0235 Valves specially adapted therefor

Abstract

Apparatus and related methods for continuous long-term non-invasive measurement of the pressure of a pulsatile fluid flowing through a flexible tube, particularly human arterial blood flow, is disclosed. Specifically, the apparatus provides a continuous calibrated pressure measurement by first undertaking a "calibration" phase comprised of determining the pressure at various pre-defined conditions of flow and, in response thereto, ascertaining the values of a plurality of coefficients each of which is associated with a corresponding term in a pre-defined function that characterizes fluid pressure in relation to pulsatile displacement of the wall of the tube; and second, undertaking a "continuous monitoring" phase comprised of determining each subsequently occurring pressure value as the pre-defined function of each corresponding pulsatile wall displacement value, and re-initiating the calibration phase at the expiration of pre-defined time intervals which adaptively change based upon current and prior results. Methods, which are particularly useful in conjunction with the disclosed apparatus, for ascertaining systolic and diastolic arterial blood pressure values are also disclosed.

Claims

1. A method of determining a measure of the diastolic arterial blood pressure in a subject comprising the steps of:

a. establishing, in response to a sequence of occlusive pressure waveform peaks and corresponding occlusive cuff pressure values occurring during deflation of an occlusive cuff, a sequence of mid-point co-ordinates, wherein one co-ordinate of each mid-point is an average of the peak amplitudes of two successive pressure waveforms and the other co-ordinate of each mid-point is an average of the occlusive cuff pressure values corresponding to each of said two peaks,

b. grouping every mid-point into an alternate one of at least two series,

c. determining the value of slope of each of a plurality of line segments, wherein each segment joins a pair of adjacent mid-points in one of said sequences,

d. testing each of said slope values against pre-defined limits to determine whether any of said mid-points is attributable to a negator or a reversal,

e. removing any pressure waveform peak and its corresponding occlusive cuff pressure value attributable to a negator or a reversal from the sequence and repeating steps (a), (b), (c) and (d) until substantially all pressure waveform peaks attributable to either negators or reversals have been removed,

f. comparing the slope of each segment in each series against a pre-defined threshold and, in response thereto, choosing an appropriate one of the segments comprising each series,

g. choosing an appropriate pressure waveform peak amplitude value that precedes the leading mid-point associated with the chosen segment in each series,

h. selecting one of the resulting chosen pressure waveform peak amplitude values as the diastolic measure.

2. The invention in claim 1 wherein said selecting step includes the step of picking that one of the chosen waveform peak amplitude values which has the minimum peak amplitude as a second diastolic measure.