Patent ID: 8287725

Claim:
An alarm arrangement, comprising: a pulse recording device configured to repeatedly register a pulse shape parameter in a peripheral body part of a subject, said pulse recording device having a pulse oximetry instrument configured to register the pulse shape parameter based on light response variations in at least one blood vessel of the subject; and a control unit configured to receive the pulse shape parameter and investigate whether the pulse shape parameter fulfills an alarm criterion, wherein if said alarm criterion is fulfilled, said control unit causes an alarm to be activated, said control unit having a processing unit configured to: calculate an initial pulse magnitude measure based on a pulse shape parameter received at a first instance; store the initial pulse magnitude measure in a memory means associated with the control unit; calculate, during a measurement period subsequent to the first instance, a respective pulse magnitude measure based on each of a number of received pulse shape parameters; and investigate, for each pulse magnitude measure in the measurement period, whether the pulse magnitude measure fulfills a decision criterion relative to the initial pulse magnitude measure, and wherein said decision criterion is fulfilled, said processing unit is further configured to generate an alarm triggering signal.