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Apparatus and method for periodically applying a pressure waveform to a limb

  • US 5,843,007 A
  • Filed: 04/29/1996
  • Issued: 12/01/1998
  • Est. Priority Date: 04/29/1996
  • Status: Expired due to Term
First Claim
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1. Apparatus for applying a pressure waveform to a patient'"'"'s limb for augmenting venous blood flow in the limb, comprising:

  • an inflatable sleeve adapted for positioning onto a limb to apply a pressure to the limb beneath the sleeve when inflated with gas;

    pressure transducing means for sensing the pressure of gas in the sleeve and for producing a sleeve pressure signal indicative of the sensed pressure;

    pressure waveform application means responsive to the sleeve pressure signal and a reference pressure waveform signal and operable by supplying gas to the sleeve at a pressure which produces a sensed pressure near a pressure indicated by a reference pressure waveform signal; and

    waveform register means for producing a reference pressure waveform signal indicative of a reference pressure waveform during a predetermined cycle time period, wherein the amplitude of the reference pressure waveform signal at any time within the cycle time period is indicative of the amplitude of the reference pressure waveform at the time and wherein the variation in amplitude of the reference pressure waveform during a predetermined time interval within the cycle time period is adapted to augment the flow of venous blood into the limb proximal to the sleeve from the limb beneath the sleeve during the predetermined time interval;

    wherein the pressure waveform application means includes a microprocessor operable by determining when to increase the pressure of gas supplied to the sleeve, decrease the pressure of gas supplied to the sleeve or maintain the pressure of gas supplied to the sleeve, and by producing a sleeve pressure mode signal having one of a plurality of predefined levels indicative of whether to increase, decrease or maintain the pressure in the sleeve, andwherein the pressure waveform application means further includes a safety circuit operable independently of the microprocessor and responsive to the sleeve pressure mode signal and having a plurality of stored levels for the sleeve pressure mode signal, wherein the safety circuit operates by comparing the level of the sleeve pressure mode signal to the plurality of stored levels for the sleeve pressure mode signal and produces a microprocessor fault signal when the level of the sleeve pressure mode signal does not correspond to one of the sets of stored levels.

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