Plethysmograph pressure correcting arrangement
First Claim
1. A method for correcting the cuff pressure in a plethysmographic arrangement for the indirect, non-invasive and continuous measurement of blood pressure in a body extremity by using a plethysmograph in a fluid-filled pressure cuff to be wrapped about said extremity, an electronic control circuit connected to the plethysmograph, and an electric pressure valve and a pressure transducer connected to said cuff, the cuff pressure being controlled by a plethysmographic signal from said plethysmograph in closed-loop operation with the aid of a servo-reference level obtained via a memory circuit in the control circuit, which servo-reference level is initially adjusted such that the cuff pressure corresponds substantially with the momentary arterial pressure, said method comprising the steps of:
- opening the closed loop of the control circuit for a short interval,in open-loop operation, adjusting the cuff pressure with the pressure valve at an intermediate pressure derived from the pressure last measured at the pressure transducer, andadjusting the servo-reference level via the memory circuit.
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Accused Products
Abstract
A method and a device for correcting the cuff pressure in the indirect, non-invasive and continuous measurement of the blood pressure in a part of the body by using a plethysmograph in a fluid-filled pressure cuff, an electronic control circuit, and an electric pressure valve. The cuff pressure is controlled by the plethysmographic signal in closed-loop operation with the aid of a servo-reference level obtained via a memory circuit. The servo-reference level, in operation of the device, is adjusted by opening the closed loop of the control circuit for a short interval, after which, in open-loop operation the cuff pressure is adjusted at an intermediate pressure derived from the pressure last measured and the servo-reference level is adjusted via the memory circuit.
40 Citations
33 Claims
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1. A method for correcting the cuff pressure in a plethysmographic arrangement for the indirect, non-invasive and continuous measurement of blood pressure in a body extremity by using a plethysmograph in a fluid-filled pressure cuff to be wrapped about said extremity, an electronic control circuit connected to the plethysmograph, and an electric pressure valve and a pressure transducer connected to said cuff, the cuff pressure being controlled by a plethysmographic signal from said plethysmograph in closed-loop operation with the aid of a servo-reference level obtained via a memory circuit in the control circuit, which servo-reference level is initially adjusted such that the cuff pressure corresponds substantially with the momentary arterial pressure, said method comprising the steps of:
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opening the closed loop of the control circuit for a short interval, in open-loop operation, adjusting the cuff pressure with the pressure valve at an intermediate pressure derived from the pressure last measured at the pressure transducer, and adjusting the servo-reference level via the memory circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. In a plethysmographic arrangement for the indirect, non-invasive and continuous measurement of the blood pressure in a body extremity, including a plethysmograph in a fluid-filled pressure cuff for wrapping about said extremity, an electric pressure connected to said cuff, and an electronic control circuit connected to said plethysmograph provided with a control loop having a differential amplifier and memory circuit in the feedback circuit for the servo-reference level, and with a control loop having a proportionate, integrate, and differentiate (PID) circuit, a parallel circuit of peak detector and trough detector connected to the pressure transducer for a pressure signal, which parallel circuit is responsive to the pressure in the pressure cuff and a state switch connected to the pressure valve for closed-open loop operation, the improvement comprising:
- a conversion circuit following the peak detector and trough detector for the pressure signal which derives an intermediate value from the peak and/or trough amplitude values of the pressure signal in closed-loop operation, and a timing circuit which switches the state switch for a short interval from closed-loop position to open-loop position, in which interval said intermediate value is supplied via the state switch to the electric pressure valve, and said memory circuit which adjusts the servo-reference level such that the average difference at the differential amplifier is zero.
- View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
Specification