Gambro Lundia Ab

St. Jude Medical Ab

Siemens Elema Ab

Siemens Aktiengesellschaft

Leif Sörnmo

Kristian Solem

Bo Olde

Lena Lundstrom

Martin Stridh

Magnus Åström

Anders Björling

Mattias Holmer

Peter Karlsson

Salvador Olmos

Magnus Aström

A filtering device receives a signal from a pressure sensor in an extracorporeal fluid circuit connected to a subject and processes the signal to separate physiological pulses, e.g. from the subject's heart, from interference pulses, e.g. from a pump in the fluid circuit. The device repeatedly (iteratively) processes a signal segment by alternately subtracting (S) a template signal from the signal segment, and applying a refinement processing (S) to the resulting difference signal to generate a new template signal. By proper selection (S) of the initial template signal, consecutive difference signals will alternately approximate the sequence of interference pulses in the signal segment and the sequence of physiological pulses in the signal segment. The refinement processing (S) aims at alternately cleaning up unwanted residuals from interference pulses and physiological pulses, respectively, in the respective difference signal, so as to improve the accuracy of the template signal between the subtractions.

Separation of interference pulses from physiological pulses in a pressure signal

A cardiac-activity based prediction of a rapid drop in a patient's blood pressure during extracorporeal blood treatment is disclosed. A proposed alarm apparatus includes a primary beat morphology analysis unit bank of secondary analysis units and an alarm generating unit. The primary beat morphology analysis unit discriminates heart beats in a received basic electrocardiogram signal, classifies each beat into one out of at least two different beat categories, and associates each segment of the signal with relevant event-type data. The event-type data and the basic electrocardiogram signal together form an enhanced electrocardiogram signal, based upon which the primary beat morphology analysis unit determines whether one or more secondary signal analyses should be performed. Depending on the enhanced electrocardiogram signal's properties, the bank of secondary analysis units performs none, one or more of up to at least two different types of secondary analyses, and for each analysis performed produces a respective test signal. The alarm generating unit receives the test signals, and triggers an alarm signal indicative of an estimated rapid blood pressure decrease, if at least one alarm criterion is fulfilled.

Detection of drastic blood pressure changes

The invention relates to prediction of a rapid symptomatic drop in a subject's blood pressure, e.g. during a medical treatment or when operating an aircraft. To this aim, a pulse shape parameter (Pps) with respect to a peripheral body part () of the subject (P) is registered by means of a pulse oximetry instrument () adapted to detect light response variations in blood vessels. An initial pulse magnitude measure is calculated based on a pulse shape parameter (Pps) received at a first instance. During a measurement period subsequent to the first instance, a respective pulse magnitude measure is calculated based on each of a number of received pulse shape parameters (Pps). It is further investigated, for each pulse magnitude measure in the measurement period, whether or not the measure fulfills a decision criterion relative to the initial pulse magnitude measure. An alarm triggering signal (&#x3b1;) is generated if the decision criterion is found to be fulfilled.

Prediction of rapid symptomatic blood pressure decrease

The invention relates to cardiac-activity based prediction of a rapid drop in a patient's blood pressure during hemodialysis. A proposed alarm apparatus includes an input interface, primary and secondary analysis units and an alarm-generating unit. An electrocardiogram signal (H) of the patient is received via the input interface by the primary analysis unit, which in response thereto produces a heart-rate-variability signal (P). The secondary analysis unit determines an intensity of ectopic beats (P) based on the electrocardiogram signal (H). The alarm-generating unit investigates whether the intensity of ectopic beats (P) is relatively low or relatively high. In case of a relatively low intensity, the unit triggers an alarm signal (&#x3b1;) indicative of an estimated rapid blood pressure decrease if the heart-rate-variability signal (P) fulfills a first alarm criterion. In case of a relatively high intensity, however, the unit triggers the alarm signal (&#x3b1;) if the intensity of the ectopic beats (P) fulfills a second alarm criterion.

An apparatus for detecting cardiac events in electrograms has a feature extraction unit that derives features of the cardiac events for discriminating among different types of cardiac events. A clustering unit groups cardiac events with similar features into respective clusters defined by predetermined cluster features. The feature extraction unit determines a feature vector describing waveform characteristics of cardiac events in the electrogram by a wavelet transform. The clustering unit determines the distance between the feature vector and corresponding cluster feature vectors in order to assign the cardiac event in question to that cluster which results in a minimum distance, providing that the minimum distance is less than a predetermined threshold value. A heart stimulator provided with such a cardiac event detecting apparatus detects the occurrence of an arrhythmia and appropriately controls a pulse stimulator to treat the arrhythmia.

Apparatus for analyzing cardiac events

In a method of and apparatus for deriving indices characterizing atrial arrhythmias, a temporally isolated portion of a digital representation of a time-domain electrical signal originating from the atria of a patient is frequency analyzed to provide a corresponding frequency spectrum. The obtained frequency spectrum is compared with a template frequency spectrum, selectively adapted dependent on previously obtained frequency spectra from different temporally isolated portions, to determine a frequency shift value and an amplitude value that optimize a correlation between the two spectra. An output representing the two determined values is used, possibly together with parameters describing the template frequency spectrum, to classify an atrial arrhythmia manifest in the digital representation.

Method of and apparatus for deriving indices characterizing atrial arrhythmias

A detector for detecting a cardiac event in an IEGM has a bank of digital filters composed of at least two filters with substantially different impulse responses corresponding to different properties of the cardiac event. The filters respectively filter different portions of the IEGM and respectively emit a value per time unit corresponding to the morphological resemblance between the IEGM and the finite impulse response. An analyzing unit combines these output values from the filters in a predetermined manner for comparison with predetermined detection criteria.

Cardiac event detector

A computerized apparatus for processing a multi-lead ECG beat signal to generate a residual signal has an averager unit for providing a template ventricular beat signal, and a subtraction unit for subtracting the template beat signal from the multi-lead ECG beat signal to generate the residual signal. An alignment stage is disposed before the subtraction unit and compares the template beat signal with an intermediate beat signal in the alignment parameter generator. A further subtraction unit may be provided to receive the multi-lead ECG beat signal and to subtract a signal representative of an estimated atrial signal therefrom to generate the intermediate beat signal. The alignment stage also modifies the template beat to increase the relative alignment of the two signals, with respect to at least spatial, characteristics, and emits the modified signal as an output for use by the subtraction unit as the template beat signal.

Electrocardiogram signal processing apparatus

In a method for correcting for non-physiological variations in ECG signals, signals recorded during a heartbeat, or a characteristic part of a heartbeat, are conditioned and digitized. Signal samples are stored in the form of an m.times.p matrix, where m is the number of samples and p is the number of leads used from measuring electrodes applied to the patient. The difference between this measuring matrix and a reference matrix is minimized by performing one or more of the operations translation, time synchronization, rotation and scaling of the measuring matrix. An apparatus for correcting for non-physiological variations in ECG signals includes a stage for conditioning signals, picked up by measuring electrodes applied to the patient, an A/D converter for digitizing the signals and a calculation unit. The calculation unit includes a storage unit for storing signal samples in the form of a m.times.p matrix, where m is the number of samples and p is the number of leads used from measuring electrodes applied to the patient, and for storing a reference matrix. The calculation unit is arranged to minimize the difference between the measuring matrix, formed from signal samples, and the reference matrix by one or more of the operations of translation, time synchronization, rotation and scaling of the measuring matrix.

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Leif Sörnmo