Artifact rejection for blood pressure monitoring

• US 3,885,551 A
• Filed: 07/19/1973
• Issued: 05/27/1975
• Est. Priority Date: 04/01/1971
• Status: Expired due to Term

• Current Assignee: Kontron (S&T AG)
• Original Assignee: Harold Lee Massie
• Inventors: Massie, Harold Lee
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/380,805
• Time in Patent Office: 677 Days
• Field of Search: 128/2.5A,2.5M,2.5P,2.5Q,2.5R,2.5T,2.6F,2.6R
• US Class Current: 600/495
• CPC Class Codes: A61B 8/04 Measuring blood pressure
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

Apparatus for automatically implementing indirect blood pressure measurement with transducer means for deriving and developing electrical signals in response to the interaction of blood pressure and cuff pressure under a varying external pressure capable of occluding an artery, and detector means for analyzing the electrical signals in terms of pulse width and rate for detection and rejection of artifact signals.

Claims

1. In an indirect blood pressure measuring apparatus having means for externally occluding an artery with pressure and varying said pressure with known pressure values allowing the artery to open and close, transducer means that responds to the interaction of blood pressure and cuff pressure to develop electrical input pulse signals including tone bursts containing a plurality of pulses, and processiNg means coupled with said pressure means for automatically responding to a selected one of said input pulse signals to provide a blood pressure measurement, the improvement comprising:

detector means, responsive to the onset of one such tone burst and coupled between said transducer means and processing means, for establishing a predetermined maximum pulse width to define as artifact a tone burst having a width in excess of said maximum width, said detector means including means for rejecting in full a tone burst determined to be artifact and for passing a non-artifact tone burst to the processing means.

2. In an apparatus according to claim 1 wherein said detector means further includes:

means for establishing a predetermined maximum pulse rate to further define as artifact a first one of two successive input pulse signals provided the second input pulse signal occurs within a predetermined period defined by said pulse rate.

3. In an apparatus according to claim 2 wherein said detector means further includes:

means for delaying an input pulse signal for a period equivalent to said maximum pulse width and maximum pulse rate, including gate means operable for passing the delayed pulse signal to the processing means; and

said reject means being coupled with said delay means and input pulse signals, and responsive to artifact for inhibiting operation of said gate means.

4. In apparatus according to claim 1 wherein said detector means comprises:

delay means for delaying an input pulse signal for a period equivalent to said predetermined maximum pulse width including gate means for passing the delayed pulse signal to the processing means as non-artifact;

said reject means being coupled with said delay means and responsive to said input pulse signals for inhibiting said gate means when said pulse width period has been exceeded.

5. In electronic apparatus, such as indirect blood pressure measuring apparatus having means for analyzing patient derived electrical signals which include tone bursts containing a plurality of pulses indicative of certain physiologic activity, in which only signals determined as non-artifact are passed and those signals determined to be artifact are selectively rejected and inhibited from passing based upon a predetermined pulse width or rate, the combination comprising:

means for delaying said signals for a first period, the first period defining a desired maximum pulse width and a second period, the first period and second period together defining a desired maximum rate, said delaying means including first means receiving said signals for providing said first period and second means directly coupled to said first means for providing said second period, said second period being caused to commence upon the termination of said first period;

first gate means connected from said delay means; and

detector means for comparing non-delayed derived signals with said delayed signals during said second period and controlling said first gate means to pass the delayed signals upon the absence of non-delayed signals and to inhibit the passage of the delayed signals upon the presence of non-delayed signals.

6. In electronic apparatus according to claim 5 wherein said delay means includes:

first one shot means energized in response to the non-delayed signals and having a first refractory period defining said maximum pulse width; and

second one shot means energized in response to said first one shot and having a second refractory period which together with said first refractory period defines said maximum pulse rate.

7. In electronic apparatus according to claim 6 wherein said delay means further includes:

bistable means responsive to said non-delayed signals and connected with said first one shot means and with said detector means, the connection with said first one shot means including a reset connection enabling said bistable means to be resettable at the end of the first refractory period uPon energization of said first one shot means.

8. In electronic apparatus according to claim 6 wherein said detector means includes:

second gate means connected from said delay means, said second gate means being enabled upon presence of non-delayed signals during said second period; and

bistable means connected from said second gate means and the input to said first one shot means and connected to said first gate means, said bistable means being resettable upon energization of said first one shot means.