EP0078090A1
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EP
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Method and device for controlling the cuff pressure in measuring the blood pressure in a finger by means of a photo-electric plethysmograph
Assignee: Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO
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Filing: 1982-10-27
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Granted: —
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Expires: 2002-10-27
Abstract
Abstract A method 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 value to be pre-adjusted, whereby for the initial adjustment, the cuff pressure or the servo-reference level as initial adjustment quantity is automatically changed continously in the control range by means of a control wave form to be supplied into 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-trough amplitude, the biggest value thereof in the control range and the associated value of the cuff pressure at servo-reference level being 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.
Inventors
- 👤 Karel Hendrik Wesseling
- 👤 Benjamino De Wit
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 12:26
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/02; A61B5/021; A61B5/02141; A61B5/022; A61B5/0225; A61B5/02255
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
187 words
A method for controlling the cuff pressure in the indirect, non-invasive, continuous measurement of the 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 value to be preadjusted, characterized in that for the sake of the 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 wave form to be supplied into the electronic control circuit, that thereby the peak-trough amplitude of the pulsatile plethysmographic signal or cuff pressure signal is detected time and again, and compared with the preceding peak-trough amplitude, the biggest value thereof in the control range and the associated value of the cuff pressure at servo-reference level being stored, which value of cuff pressure or servo-reference level at the end of the initial adjustment is used as set value for the measurement of the blood pressure.
Claim 2
Independent Claim
187 words
A method for controlling the cuff pressure in the indirect, non-invasive, continuous measurement of the 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 value to be preadjusted, characterized in that for the sake of the 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 wave form to be supplied into the electronic control circuit, that thereby the peak-trough amplitude of the pulsatile plethysmographic signal or cuff pressure signal is detected time and again, and compared with the preceding peak-trough amplitude, the biggest value thereof in the control range and the associated value of the cuff pressure at servo-reference level being stored, which value of cuff pressure or servo-reference level at the end of the initial adjustment is used as set value for the measurement of the blood pressure.
Claim 3
Dependent Claim
67 words
A method according to claim 1, in which in open-loop operation first the cuff pressure is adjusted to a value between diastolic and systolic pressure, such that the pulsatile plethysmographicsignal is at maximum, characterized in that in open-loop operation the cuff pressure is changed stepwise and that each following pressure step increase is initiated by termination of the current peak-trough detection of the pulsatile plethysmographic signal. -
Claim 4
Dependent Claim
21 words
A method according to claim 2, characterized in that the cuff pressure in its pressure steps is changed in exponential increase.
Claim 5
Dependent Claim
37 words
A method according to claim 2 or 3, characterized d in that the loop amplification in the servo-control loop is adjusted in inverse proportion to the peak-trough differential amplitude in the pulsatile plethysmographic signal in open-loop operation.
Claim 6
Independent Claim
31 words
A method according to one of claims 2-4, characterized in that, in absence of natural intra-arterial pressure pulsations, artificial pressure pulsations are superposed on the control wave form to be introduced.
Claim 7
Independent Claim
159 words
A device to carry out the method according to one of the preceding claims, for the indirect, non-invasive, continuous measurement of the blood pressure in a finger, which device comprises a photo-electric plethysmograph in a fluid-filled pressure cuff and associated light source and light detector, an electric pressure valve and an electronic control circuit provided with a differential amplifier, on the one input and the other input of which respectively the plethysmographic signal and a servo-reference level is supplied, characterized in that the electronic circuit further comprises a wave form generator to supply a predetermined control wave form to the circuit; two control loops of which one comprises the differential amplifier having a feed-back circuit for the servo-reference level and of which the other comprises a PID-circuit, the input of which is connected in parallel to the input of the differential amplifier and the output of which is connected to the electric pressure valve; and a logic control circuit.
Claim 8
Dependent Claim
61 words
A device according to claim 6, characterized in that one of the two control loops is connected to an adjustment loop consisting of a detection circuit for the pulsatile plethysmographic or cuff pressure signal and a memory circuit for the temporary storage of successive peak-trough differential amplitudes of said pulsatile signal and the associated value of cuff pressure or servo-reference level.
Claim 9
Dependent Claim
77 words
A device according to claim 7, provided with a switch for open-closed loop operation, characterized in that the switch is connected with its output to the electric pressure valve, 7 with an input for open-loop operation to the wave form generator, and with another input for closed-loop operation to the output of the PID circuit respectively, that the adjustment loop having the detection circuit and memory circuit is connected after the control loop having the differential amplifier.
Claim 10
Dependent Claim
96 words
A device according to claim 8, characterized in that the detection circuit comprises a parallel circuit of a peak detector and a trough detector, that the memory circuit comprises a first memory for the peak-trough differential amplitudes and a second memory for the cuff pressure values, whereby a comparator circuit is used to compare each detected peak-trough differential amplitude with the preceding peak-trough differential amplitude and in case of exceeding same to store the current differential amplitude in the first memory and the associated cuff pressure value from the control wave form in the second memory.
Claim 11
Dependent Claim
109 words
A device according to claim 8 or 9 , characterized in that the feed-back circuit of the differential amplifier comprises an integrator, and that the switch has a further input, connected in open-loop operation to the second memory, in order to supply - under control of the logic control circuit, after the pressure control range has been passed through in the one open-loop position - the cuff pressure value corresponding to the maximum peak-trough differential amplitude to the electric pressure valve during a time sufficient to have the differential amplifier-integrator circuit adjust its output signal to the time average level, after which the switch passes into the closed-loop position.
Claim 12
Dependent Claim
61 words
. 11. A device acccrding to claim 9 or 10, characterized in that the output of the first memory is also connected to a divider circuit, taken up in the output of the PID-circuit, in. order to adjust the loop amplification in the PID control loop in inverse proportion to the peak-trough differential amplitude in the plethysmographic signal in open-loop operation.
Claim 13
Independent Claim
59 words
A device according to one of the preceding claims 6-11, characterized in that the wave form generator is a step generator and that the peak detector and the trough detector, at the end of each peak and trough detection respectively, supply a ready-signal to the logic control circuit, which subsequently triggers the step generator for the next step. -
Claim 14
Dependent Claim
24 words
A device according to claim 12, characterized in that the step generator is embodied such that the step curve shows an exponentially increasing step.
Claim 15
Independent Claim
28 words
A device according to one of claims 6-11, characterized in that the wave form generator is embodied such that it supplies a monotone continuously increasing control wave form.
Claim 16
Independent Claim
50 words
A device according to one of claims 8-14, characterized in that a pulsation generator is applied, in order to superpose, in the absence of natural intra-arterial pressure pulsations, artificial pressure pulsations on the control wave form of the wave form generator to be supplied to the input of said switch.
References Cited (Backward Citations)
NL7605187A
Cited
US4105021A
Cited
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