Oscillometric blood pressure monitor with enhanced cuff pressure control

• US 5,579,776 A
• Filed: 01/13/1995
• Issued: 12/03/1996
• Est. Priority Date: 01/13/1995
• Status: Expired due to Term

• Current Assignee: Critikon Co. LLC
• Original Assignee: Johnson & Johnson Medical Incorporated (Johnson & Johnson)
• Inventors: Medero, Richard
• Primary Examiner(s): Sykes, Angela D.
• Assistant Examiner(s): NASSER, ROBERT L
• Application Number:
  US08/372,137
• Time in Patent Office: 690 Days
• Field of Search: 128/672, 128/677, 128/680-3, 128/687
• US Class Current: 600/493
• CPC Class Codes: A61B 5/02225 using the oscillometric method
• CPC Class Codes: A61B 5/0225 the pressure being controlled by electric signals, e.g. derived from Korotkoff sounds

Abstract

An automated sphygmomanometer in which the so-called "air effect" (a slow rise or fall in cuff pressure caused by step inflates or deflates) is substantially eliminated by deflating (inflating) the pressure cuff to a pressure lower (higher) than the target pressure, waiting a short time interval, and then inflating (deflating) the pressure cuff to the target pressure. The driving force that causes the air effect to settle out after a step inflate or deflate is proportional to the size of the step change in pressure and is thus greatest during the wait time before the pressure cuff is inflated or deflated to the target pressure. Once at the target pressure, the remaining air effect is counteracted by the incremental air effect introduced by the latter inflate or deflate so that the air effect cancels out. The techniques of the invention provide most improved results for large inflates and deflates of 20 mm Hg or more or first deflates after a complete inflate of the pressure cuff where the air effects are most pronounced.

Claims

1. An automated sphygmomanometer apparatus, comprising:

an inflatable and deflatable pressure cuff;

inflating means operatively coupled to said cuff for selectively applying a medium under pressure to said cuff for inflating and pressurizing said cuff;

cuff pressure sensing means coupled to said cuff for sensing cuff pressure including any blood pressure oscillations therein;

deflating means operatively coupled to said cuff for selectively relieving pressure from said cuff; and

control means for measuring a patient'"'"'s blood pressure from a cuff pressure sensed by said cuff pressure sensing means, said control means controlling said inflating means to inflate said cuff and said deflating means to deflate said cuff during a blood pressure measurement of said patient, said control means instructing said inflating means to inflate said cuff to a predetermined pressure above an estimated systolic pressure of said patient at a beginning of a blood pressure measurement cycle, instructing said deflating means to deflate said cuff in pressure steps to respective pressures lower than respective target pressures and, after predetermined intervals of time, instructing said inflating means to inflate said cuff to said respective target pressures for a determination of the existence and magnitude of blood pressure oscillations at each of said respective target pressures by said cuff pressure sensing means.

2. An automated sphygmomanometer apparatus, comprising:

an inflatable and deflatable pressure cuff;

inflating means operatively coupled to said cuff for selectively applying a medium under pressure to said cuff for inflating and pressurizing said cuff;

cuff pressure sensing means coupled to said cuff for sensing cuff pressure including any blood pressure oscillations therein;

deflating means operatively coupled to said cuff for relieving pressure from said cuff; and

control means for measuring a patient'"'"'s blood pressure from a cuff pressure sensed by said cuff pressure sensing means, said control means controlling said inflating means to inflate said cuff and said deflating means to deflate said cuff during a blood pressure measurement of said patient, said control means instructing said inflating means during a blood pressure measurement cycle to inflate said cuff in pressure steps to respective pressures above respective target pressures, and, after predetermined intervals of time, instructing said deflating means to deflate said cuff to said respective target pressures for a determination of the existence and magnitude of blood pressure oscillations at each of said respective target pressures by said cuff pressure sensing means.

3. A method of measuring blood pressure of a patient using an automatic oscillometric blood pressure monitor comprising a pressurized cuff, means for inflating and deflating said cuff in pressure steps to respective pressure levels during a blood pressure measurement, and means for measuring arterial pressure oscillation complexes at said respective pressure levels through measurement of time varying pressures within said cuff, said method comprising the steps of:

(a) inflating said cuff about an artery of the patient until said cuff is at a first pressure level a predetermined amount above the patient'"'"'s estimated systolic pressure;

(b) deflating said cuff from said first pressure level to a second pressure level below a target pressure level;

(c) after a predetermined interval of time, inflating said cuff from said second pressure level to said target pressure level;

(d) searching for arterial pressure oscillation complexes at said target pressure level; and

(e) repeating steps (b)-(d) for subsequent blood pressure levels during said blood pressure measurement until arterial pressure oscillation complexes of a predetermined quality are detected in step (d) for a sufficient number of pressure levels to permit a blood pressure determination for the patient.

4. A method of measuring blood pressure of a patient using an automatic oscillometric blood pressure monitor comprising a pressurized cuff, means for inflating and deflating said cuff in pressure steps to respective pressure levels during a blood pressure measurement, and means for measuring arterial pressure oscillation complexes at said respective pressure levels through measurement of time varying pressures within said cuff, said method comprising the steps of:

(a) inflating said cuff about an artery of the patient until said cuff is at a first pressure level a predetermined amount above a target pressure level;

(b) after a predetermined interval of time, deflating said cuff from said first pressure level to said target pressure level;

(c) searching for arterial pressure oscillation complexes at said target pressure level; and

(d) repeating steps (a)-(c) for higher target pressure levels during said blood pressure measurement until arterial pressure oscillation complexes of a predetermined quality are detected in step (c) for a sufficient number of pressure levels to permit a blood pressure determination for the patient.

5. An automated sphygmomanometer apparatus, comprising:

an inflatable and deflatable pressure cuff;

inflating means operatively coupled to said cuff for selectively applying a medium under pressure to said cuff for inflating and pressurizing said cuff;

cuff pressure sensing means coupled to said cuff for sensing cuff pressure including any blood pressure oscillations therein;

deflating means operatively coupled to said cuff for relieving pressure from said cuff; and

control means for measuring a patient'"'"'s blood pressure from a cuff pressure sensed by said cuff pressure sensing means, said control means controlling said inflating means to inflate said cuff and said deflating means to deflate said cuff during a blood pressure measurement of said patient, said control means instructing said inflating means and said deflating means during a blood pressure measurement cycle to inflate/deflate said cuff in pressure steps to respective pressures beyond respective target pressures in a direction of inflation/deflation and, after predetermined intervals of time, instructing said deflating means and said inflating means to deflate/inflate said cuff back to said respective target pressures for a determination of the existence and magnitude of blood pressure oscillations at each of said respective target pressures by said cuff pressure sensing means.

6. A method of measuring blood pressure of a patient using an automatic oscillometric blood pressure monitor comprising a pressurized cuff, means for inflating and deflating said cuff in pressure steps to respective pressure levels during a blood pressure measurement, and means for measuring arterial pressure oscillation complexes at said respective pressure levels through measurement of time varying pressures within said cuff, said method comprising the steps of:

(a) inflating/deflating said cuff about an artery of the patient until said cuff is at a first pressure level a predetermined amount beyond a target pressure level in a direction of inflation/deflation;

(b) after a predetermined interval of time, deflating/inflating said cuff from said first pressure level back to said target pressure level;

(c) searching for arterial pressure oscillation complexes at said target pressure level; and

(d) repeating steps (a)-(c) for respective target pressure levels during said blood pressure measurement until arterial pressure oscillation complexes of a predetermined quality are detected in step (c) for a sufficient number of pressure levels to permit a blood pressure determination for the patient.