Method and device for controlling the cuff pressure in measuring the blood pressure in a finger by means of photo-electric plethysmograph
First Claim
1. An improved method for controlling cuff pressure in an indirect, non-invasive, continuous measurement of blood pressure in a finger by using a photo-electric plethysmograph providing a pulsatile plethysmographic signal and used with a fluid-filled pressure cuff, an electronic control circuit having an open and closed-control loop operation, an electric pressure valve connected to said cuff and a cuff pressure transducer providing a cuff pressure signal, the cuff pressure being controlled by the plethysmographic signal in closed-loop operation by means of a servo-reference level, so that the arterial volume is maintained at a preadjusted value, wherein the improvement includes the steps of:
- continuously changing, within a control range, for initial open loop adjustment, the cuff pressure or the servo-reference level by means of a control wave form provided to the electronic control circuit;
periodically detecting each peak-trough differential amplitude of the pulsatile plethysmographic signal or cuff pressure signal;
comparing each said peak-trough differential amplitude with the preceding peak-trough differential amplitude; and
storing the associated value of peak-trough differential amplitude in the control range and the associated value of the cuff pressure or servo-reference level, and using said associated value of cuff pressure or servo-reference level at the end of the initial adjustment as the for set value measurement of the blood pressure after initial open-loop adjustment.
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Accused Products
Abstract
Arrangement for controlling the cuff pressure in the indirect, non-invasive, continuous measurement of blood pressure in a finger by using a photo-electric plethysmograph in a fluid-filled pressure cuff, an electronic control circuit and an electric pressure valve, the cuff pressure being controlled by the plethysmographic signal in closed-loop operation by means of a servo-reference level, so that the arterial volume is maintained at a pre-adjusted value. For initial adjustment, the cuff pressure or the servo-reference level as initial adjustment quantity is automatically changed continuously in the control range by means of a control waveform supplied to the electronic control circuit, that thereby the peak-through amplitude of the pulsatile plethysmographic signal or cuff pressure signal is detected time and again, and compared with the preceding peak-through amplitude. The biggest value thereof in the control range and the associated value of the cuff pressure at servo-reference level are stored, which value of cuff pressure or servo-reference at the end of the initial adjustment is used as set value for the measurement of the blood pressure.
64 Citations
15 Claims
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1. An improved method for controlling cuff pressure in an indirect, non-invasive, continuous measurement of blood pressure in a finger by using a photo-electric plethysmograph providing a pulsatile plethysmographic signal and used with a fluid-filled pressure cuff, an electronic control circuit having an open and closed-control loop operation, an electric pressure valve connected to said cuff and a cuff pressure transducer providing a cuff pressure signal, the cuff pressure being controlled by the plethysmographic signal in closed-loop operation by means of a servo-reference level, so that the arterial volume is maintained at a preadjusted value, wherein the improvement includes the steps of:
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continuously changing, within a control range, for initial open loop adjustment, the cuff pressure or the servo-reference level by means of a control wave form provided to the electronic control circuit; periodically detecting each peak-trough differential amplitude of the pulsatile plethysmographic signal or cuff pressure signal; comparing each said peak-trough differential amplitude with the preceding peak-trough differential amplitude; and storing the associated value of peak-trough differential amplitude in the control range and the associated value of the cuff pressure or servo-reference level, and using said associated value of cuff pressure or servo-reference level at the end of the initial adjustment as the for set value measurement of the blood pressure after initial open-loop adjustment. - View Dependent Claims (2, 3, 4, 5)
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6. In a device for controlling cuff pressure in an indirect, non-invasive, continuous measurement of blood pressure in a finger, which device comprises a photo-electric plethysmograph providing a pulsatile plethysmographic signal and used with a fluid-filled pressure cuff and associated light source and light detector, an electric pressure valve connected to the cuff, a cuff pressure transducer providing a cuff pressure signal and an electronic control circuit having an open and closed control-loop operation and including a differential amplifier having a first and second inputs respectively receiving the plethysmographic signal and a servo-reference level, the improvement comprising:
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a wave form generator which supplies a control wave form, continuously changing in a control range, to the electronic control circuit; two control loops of which one comprises the differential amplifier having a feed-back circuit for the servo-reference level and the other of which comprises a proportionate integrate-differentiate (PID) circuit, the input of which is connected in parallel to an input of the differential amplifier and the output of which is connected to the electric pressure valve; and a logic control circuit connected to said wave form generator and to said two control loops. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification