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Biomedical subjects

M Rother

Publications and source records attributed to M Rother.

13 recordsLinked to original sources
PubMed1992

[Application of Fourier transformation as the basic algorithm for processing cardiorespiratory data of newborn infants].

The multiple possibilities for the application of Fast Fourier Transformation (FFT) in the cardiorespirography of neonates are shown as a summary of our own results. The basis is the power spectral analysis of instantaneous heart rate and respiratory movements, which can be complemented by a coherence analysis of both parameters. A model-aided method for quantification of respiratory sinus arrhythmia (RSA) as an additional application for power spectral and coherence analysis is discussed. The realization of Hilbert transformation by FFT makes possible the interval-related calculation of respiration rate. The necessity of this supplementation, as well as the resulting strategies of additional processing steps are emphasized. The results is a concept of signal processing which increases the efficiency of previously employed methods in computer-aided cardiorespirography.

Algorithms↗
PubMed1991

Use of discrete Hilbert transformation for automatic spike mapping: a methodological investigation.

On the basis of discrete Hilbert transform (DHT) realised by fast Fourier transform (FFT), a new strategy for automatic spike mapping is introduced. The further computation of the EEG time series after DHT results in the time series of the momentary power and the momentary frequency. Both are used for the solution of the main requirements of automatic spike mapping. The spike-mapping concept introduced meets the requirements of efficient automatic spike detection and also has an insensitivity with regard to EMG interference and transient signal components, a frequent cause of false positive detections. Additionally, there are advantages if the momentary power of the spike is mapped instead of the spike potential. The use of momentary power makes a combination of power spectral mapping and spike-mapping strategies possible.

Algorithms↗
PubMed1991

Using discrete Hilbert transformation for interval-related calculation of the respiration rate in neonates.

From the basis of the fast Fourier transformation (FFT), the discrete Hilbert transformation (DHT) is used to compute the instantaneous respiration rate in neonates. This interval-related computation of respiration rate must be combined with a concept of adaptive filtration of the respiratory movements. This strategy is performed by adaptive recursive estimations of mean values with different adaptation constants. Additionally, a frequency band limitation is carried out on the basis of the peak characteristic of the power spectrum (respiratory movements). By means of the adaptive estimation of the variance of respiratory movements, an amplitude-time window is calculated to choose between epochs with breaths and apnoea.

Algorithms↗
PubMed1991

Parameters for sensitive cerebral monitoring during the neonatal period in intensive care medicine.

In order to bring about further reduction of neonatal mortality and morbidity, immediate and highly sensitive detection of brain-threatening situations is necessary. We investigated 52 newborns by means of 8-channel EEG recorded with normal (15 mm/s) and compressed write-out (1 cm/min). A correct estimation of amplitude of background activity was possible by both methods. For differentiation between healthy newborns and newborns at risk, the right hemisphere amplitude of the interburst period was the most appropriate. The amplitude of the continuous EEG and the interburst period was reduced in the group of newborns at risk. In the group of the most severely disturbed newborns there was an amplitude difference between both hemispheres with greater reduction over the right hemisphere. These results emphasize the importance of the amplitude of background activity for prognostication and the necessity of using 2 interhemispheric derivations for an independent estimation of changes in both hemispheres.

Brain↗
PubMed1991

Experimental and clinical studies of neonatal eeg mapping--methodical prerequisites and data interpretation.

To investigate whether the sampling theorem was fulfilled up to now in experimental and clinical EEG-mapping of neonates and to determine the "smearing effect" of EEG transmission by the leading media up to the skin, EEG-maps from 5 slightly anaesthetized term newborn piglets and 8 healthy human newborns were calculated. A spatial sampling rate of 1-2 cycles per cm is necessary for a sufficient reproduction of surface EEG topology in newborn piglets showing activity maxima within motor projection zones. In human neonates, 8-channel mapping gave insufficient results, whereas state and EEG pattern related 16-channel maps provided sufficiently constant, but not complete pattern. Simultaneous maps from epidural and epiossal, and epiossal, and surface recordings in newborn piglets showed only small "smearing" effects. We conclude, the more topical interpretation chances exist, like in neonates with smaller "smearing" effects of transmission media, the more complete uptake of original data for mapping is necessary. Up to now, it is done seldomly.

Animals↗
PubMed1990

EEG spectral analysis in newborns with and without severe brain damage at different conceptional ages. A preliminary report.

Spectral power (SP) analysis of neonatal discontinuous EEG pattern of bilateral Fp-T and T-0 derivations has been performed in 5 newborns with no or mild brain damage and in 5 newborns with severe brain damage matched for conceptional age (30-39, week). Discontinuous EEG was separated in interburst and burst intervals. SP of all frequency bands was depressed in newborns with severe brain damage, with the depression being more pronounced during interburst intervals. Surprisingly, a prominent depression of the SP of the derivations of the right hemisphere and of the delta frequency bands of severely handicapped newborns was found. Calculation of coherence between homologous bipolar derivations does not improve the possibilities to separate both groups.

Brain Damage, Chronic↗
PubMed1990

[EEG and evoked potential mapping].

By spectral EEG-mapping and EP-mapping, especially the topologic dimension of electrical brain activity can be evaluated for clinical use. On the other hand, this method allows the highest solution from all functional imaging procedures within the time dimension of brain activity. On the other hand, the ability of topological solution is limited. But the latter is probably better than hitherto assumed and surprisingly well at least regarding neonates. However, several methodological prerequisites described here must be fulfilled. From the pathophysiological point of view, the limits must be considered besides the diagnostic possibilities. Meanwhile, spectral EEG-mapping and EP-mapping are diagnostically used in all main fields of traditional EEG-analysis, like seizures and in the preadiagnostics of tumors a.o. Also in the diagnostics of cerebrovascular disease including transient ischemic attacks, the EEG-mapping and/or EP-mapping are useful within the total diagnostics. There is a similar situation in the diagnostics of degenerative brain disorders. But the significance of frequently described changes inpsychoses, partly also neuroses and other functional disorders is not clear. Altogether, this non-invasive, economically most favourable method for the functional imaging procedures in brain diagnostics is promising to extent the routine diagnostics also to a more precise manner.

Brain↗
PubMed1989

[Polygraphic studies of newborn infants at risk using acoustic stimulation close to and above the threshold level].

16 newborns were investigated by means of polygraphy (EEG, respirography, heart rate, psychogalvanic reflex and behavioural observations). They were acoustically stimulated (125, 750, 15000 and 3000 Hz, with stepwise increase of the intensity by 10 dBA) during the period of quiet sleep. Partial vegetative reactions appeared in 11 newborns between a stimulation intensity of 30 to 50 dBA. Changes of breathing were initially observed. A further increase of intensity caused reactions in heart rate, psychogalvanic reflex and also body movements. The EEG and behavioural states were never changed at this level of intensity. Reactions in these parameters were recurrently observable if stimulation intensity was higher than 80 dBA. Only half of all stimulations were followed by reactions. The results verify decreased threshold intensity to evoke partial vegetative reactions in newborns at risk and the same sequence of additional reactions in EEG and behavioural states as in healthy newborns following increasing stimulation intensity.

Acoustic Stimulation↗
PubMed1979

Lymphocyte proliferation to phytohemagglutinin (PHA) in hepatitis B antigen-positive and -negative hepatitis.

Lymphocytes from patients with HBs-Ag-positive and -negative acute, chronic-persistent, and chronic-active hepatitis, from healthy controls and from patients with alcoholic liver cirrhosis were tested under standardized conditions. These included use of a single charge of Phytohemagglutinin (PHA-P) dissolved and diluted in one operation, of a single pool of homologous serum of the major blood group AB found free of HBs-Ag and cytotixic factor, and elaboration of PHA dose response curves in the presence of autologous and homologous serum in each case examined. During the early phase of acute virus hepatitis B and non-B, and in HBs-Ag-positive chronic persistent and active hepatitis, hyperresponsiveness of lymphocytes to PHA was observed independently of the source of the serum present in the culture. Lymphocyte responsiveness returned to normal in the later phase of acute hepatitis and depressed in alcoholic liver cirrhosis and in cases of HBs-Ag-positive chronic active hepatitis in which cirrhosis had developed. Although the cause of these alterations in lymphocyte responsiveness is not completely understood, the central role of a primary change of the lymphocytes themselves affecting their ability to react to PHA seems probable.

Acute Disease↗
PubMedDate not supplied

High-frequency and low-frequency heart-rate fluctuation analysis in newborns--a review of possibilities and limitations.

Respiratory sinus arrhythmia (RSA) has been traditionally defined as the high-frequency component of heart-rate fluctuations (HRF) synchronous with the respiratory movements (RM), i.e., the frequency of RSA corresponds to the respiration rate. It can be shown that at defined relations of mean heart and respiration rate some essential effects must be taken into consideration in studies using RSA parameters. The relevance of these effects is shown and a new strategy of RSA quantification demanded, at least in neonates. The diagnostic importance, physiological background and future application of the low-frequency components of the neonatal HRF are reviewed on the basis of our own results. Nonrespiratory cardiovascular HRF cannot always be detected in the neonate by power spectral analysis. Movement-related HRF have a potential diagnostic importance per se, but may also artefactually disturb the quantification of other HRF components. Long-term trends can be used to describe sleep-state related trends and their disturbances.

Arrhythmia, Sinus↗