Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
  • H03H17/00—Networks using digital techniques
  • H03H17/02—Frequency selective networks
  • H03H17/0219—Compensation of undesirable effects, e.g. quantisation noise, overflow

Definitions

• FIG. 1 illustrates a conventional automatic blood pressure gauge, which includes a resilient inflatable cuff 2 connected via a tube 4 to an electric pump 6.
• the microprocessor in the automatic blood pressure gauge typically executes an algorithm employing a high-pass filter (HPF) to extract from the average cuff pressure signal, the heart-rate pressure pulsations coupled to the cuff by the blood vessels in the patient's arm.
• HPF high-pass filter
• the filter is a 4th order Bessel filter with a -3 dB cut-off frequency of 0.75 Hz.
• Figure 3 illustrates the sampled pressure signal at the output of the HPF.
• the settling time effect causes distortion in the amplitude of legitimate pulses that appear at the output of the HPF after the occurrence of the transition, thereby delaying the accurate detection and measurement of the blood pressure of the patient.
• the distortion effect is at its maximum at time sample 831 , and continues to about sample time 950 (note, the increasing amplitude of pulsatile components is representative of the cuff pressure approaching the mean arterial pressure of the patient).
• Figure 3 previously described, illustrates the distortion effect in the pulsatile component of the measured blood pressure pulses due to the pressure transition shown in Figure 2;
• Figure 6 illustrates the generation of a smoothed transition ramp in accordance with a further aspect of the present invention.
• HPF high-pass filter
• the average slope of the pressure signal will either be 0 mmHg/sec during the pressure-hold stage or -4 mmHg/sec during the deflation stage.
• a dashed-line waveform 500 illustrates the output of the filter without use of the inventive filter reset scheme
• a solid-line waveform 502 illustrates the improvement when using the filter reset scheme of the invention.
• FIG. 6 shows details of a cuff pressure signal 602 at the point where a blood pressure pulsation is occurring during deflation. Notice that the slope of the cuff pressure signal is varying due to the presence of the pulsation.
• time samples 832 and beyond are shown for perspective only, and they would have not yet been sampled when the filter was reset just after time sample 831.
• the slope between time samples 830 and 831 is the instantaneous slope mentioned earlier and the artificial ramp would be connected to time sample 830.
• the ramp's slope will converge on the expected slope and will remain there for the majority of the samples in the ramp. 4.
• the ramp is 300 samples in length (6 seconds of clocking the HPF at its normal rate), it is completed.

Landscapes

• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Computer Hardware Design (AREA)
• Mathematical Physics (AREA)
• Measuring Pulse, Heart Rate, Blood Pressure Or Blood Flow (AREA)
• Networks Using Active Elements (AREA)
• Oscillators With Electromechanical Resonators (AREA)
• Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
• Filters And Equalizers (AREA)
• Magnetic Resonance Imaging Apparatus (AREA)
• Measurement And Recording Of Electrical Phenomena And Electrical Characteristics Of The Living Body (AREA)
• Measurement Of Unknown Time Intervals (AREA)
• Emergency Protection Circuit Devices (AREA)

Priority Applications (6)

Applications Claiming Priority (2)

Publications (1)

Family

ID=22771627

Family Applications (1)

Country Status (8)

Families Citing this family (2)

Citations (5)

Family Cites Families (5)

• 1998
  • 1998-12-08 US US09/207,697 patent/US6249796B1/en not_active Expired - Lifetime
• 1999
  • 1999-11-22 AT AT99962831T patent/ATE259116T1/de not_active IP Right Cessation
  • 1999-11-22 JP JP2000587440A patent/JP2002532120A/ja not_active Ceased
  • 1999-11-22 WO PCT/US1999/027707 patent/WO2000035087A1/en not_active Ceased
  • 1999-11-22 EP EP99962831A patent/EP1138117B1/en not_active Expired - Lifetime
  • 1999-11-22 DE DE69914631T patent/DE69914631T2/de not_active Expired - Lifetime
  • 1999-11-22 CA CA002353892A patent/CA2353892A1/en not_active Abandoned
• 2001
  • 2001-06-07 NO NO20012819A patent/NO20012819L/no not_active Application Discontinuation

Patent Citations (5)

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