Patent ID: 8114025

Claim:
A method for controlling the pressure in at least one inflatable cuff of a blood pressure measuring apparatus in closed-loop operation, where the pressure on the cuff equals the arterial pressure, with a plethysmographic sensor device, whereby a plethysmographic signal PG and a cuff pressure signal BP are obtained, comprising the following steps: a) in a first concentric inner control loop the cuff pressure signal BP is used as control variable and is fed into a difference amplifier as a first input signal, b) in a second concentric outer control loop, which is simultaneously active with the first concentric inner control loop for closed-loop operation, the plethysmographic signal PG, with its mean value PG suppressed, is fed into a controller and is added to a set-point signal SP, and a target signal SW is generated, which is fed into said difference amplifier as a second input signal, c) an output signal AS of the difference amplifier is used to control at least one valve connected to a pressure source, which in turn regulates the pressure in the cuff, and d) no re-adjustments of set-point signal SP during open-loop operation with the help of a state-switch and timing-circuits.