Actigraphy, the long-term measurement of human movement with a small solid state recorder, is gaining acceptance as a useful method in many research fields. Currently available actigraphs assess or estimate the movement duration per time interval. However, the output gives no information on movement type or intensity, and cannot be used in subjects suffering from tremor. The present paper describes a new type of actigraph, that has been developed primarily for the long-term evaluation of motor symptoms in Parkinson patients. The device is the first to discriminate tremor from other movements and to assess both duration and intensity of the two types of movement. It is based on a Motorola 68HC805B6 microcontroller and contains: an accelerometer, programmable gain stages, programmable low- and highpass filters, a programmable level comparator, a peak detector, interface circuits, a real time clock, data storage, and control circuitry. The micro-controller performs a period amplitude sequence analysis (PASA) on the conditioned accelerometer signal, and stores four output variables (tremor duration, tremor amplitude, movement duration, and movement amplitude) at the end of programmable time intervals. The analysis of fluctuations in the motor symptoms of, e.g., Parkinson patients using this actigraph can be of great help in the pharmacological management of symptoms.
IntroductionDual chamber pacing systems have been in use for more than ten years and have proven to provide superior hemodynamics compared to single chamber pacing systems. Since their introduction only minor modifications to tbe basic bebavior have been introduced. Tbe main principle of most dual cbamber pacemakers still consists of following all sensed atrial events, providing tbe ventricular rate does not exceed a certain, programmable upper rate limit. Pacemakers that control their upper rate by sensor information are becoming available, but so far only one pacemaker automatically reduces the upper rate limit when a pathological atrial rhythm is detected. A next step in dual cbamber pacing may consist of reliable beat-to-beat diagnosis of atrial sensed events. Tbis information in turn can influence the pacemaker response. Adaptive mode switching, whereby on a beat-to-beat basis tbe optimum pacemaker response is determined, is intended to provide maximum tracking of sensed atrial beats, with elimination of synchronization to pathological atrial rhythm.In tbis study beart rate variation is investigated and an atgoritbm that should reliably detect pathological rhythms based on tbe analysis of heart rhytbm alone is tested.
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