Olaf Hochmuth

Computer simulation of the measured respiratory impedance in newborn infants and the effect of the measurement equipment

The forced oscillation technique (FOT) is a non-invasive method to investigate lung mechanics. FOT does not require active cooperation and therefore it seems to be useful for lung function measurements in newborn infants. The aims of this simulation study were to investigate the effects of development and growth of the lung, pulmonary inhomogeneities and the measurement equipment on the respiratory impedance (Zrs). The respiratory impedance was simulated by using four lung models with lumped parameters in the frequency range of 3-50 Hz considering resistive and elastic resistances of the respiratory system and the inertance of breathing air and tissue. The simulation has shown that the maturation of lungs produces only a parallel shifting of the real and imaginary part of the impedance curves whereas respiratory diseases change the course of the curves. Furthermore, a high influence of the measurement equipment (e.g. compliance of the face mask, endotracheal tube leaks) on Zrs was found. In conclusion, the simulation has shown that FOT offers a deeper insight in the structure of the respiratory system. However, the technical requirements for accurate measurements in newborns are very high.

EEG artifact elimination by extraction of ICA-component features using image processing algorithms.

Artifact rejection is a central issue when dealing with electroencephalogram recordings. Although independent component analysis (ICA) separates data in linearly independent components (IC), the classification of these components as artifact or EEG signal still requires visual inspection by experts. In this paper, we achieve automated artifact elimination using linear discriminant analysis (LDA) for classification of feature vectors extracted from ICA components via image processing algorithms. We compare the performance of this automated classifier to visual classification by experts and identify range filtering as a feature extraction method with great potential for automated IC artifact recognition (accuracy rate 88%). We obtain almost the same level of recognition performance for geometric features and local binary pattern (LBP) features. Compared to the existing automated solutions the proposed method has two main advantages: First, it does not depend on direct recording of artifact signals, which then, e.g. have to be subtracted from the contaminated EEG. Second, it is not limited to a specific number or type of artifact. In summary, the present method is an automatic, reliable, real-time capable and practical tool that reduces the time intensive manual selection of ICs for artifact removal. The results are very promising despite the relatively small channel resolution of 25 electrodes.

Infrared-monitored cold response in the assessment of Raynaud's phenomenon.

Background.  Evaluation of treatments for Raynauds phenomenon (RP) requires objective response parameters in addition to clinical activity scores. Thermographic monitoring of fingertip re‐warming after cold challenge has been widely used but usually requires sophisticated equipment. We have previously shown that fingertip re‐warming after cold challenge follows a first‐order transient response curve that can be described by a single variable, designated τ.

Automated EEG artifact elimination by applying machine learning algorithms to ICA-based features

OBJECTIVE Biological and non-biological artifacts cause severe problems when dealing with electroencephalogram (EEG) recordings. Independent component analysis (ICA) is a widely used method for eliminating various artifacts from recordings. However, evaluating and classifying the calculated independent components (IC) as artifact or EEG is not fully automated at present. APPROACH In this study, we propose a new approach for automated artifact elimination, which applies machine learning algorithms to ICA-based features. MAIN RESULTS We compared the performance of our classifiers with the visual classification results given by experts. The best result with an accuracy rate of 95% was achieved using features obtained by range filtering of the topoplots and IC power spectra combined with an artificial neural network. SIGNIFICANCE Compared with the existing automated solutions, our proposed method is not limited to specific types of artifacts, electrode configurations, or number of EEG channels. The main advantages of the proposed method is that it provides an automatic, reliable, real-time capable, and practical tool, which avoids the need for the time-consuming manual selection of ICs during artifact removal.

In vitro investigations of jet-pulses for the measurement of respiratory impedance in newborns.

The aim of this in vitro study was to investigate the measuring range and accuracy of a miniaturized equipment for respiratory impedance (Zrs) measurements in newborns using jet-pulses. Brief flow pulses (peak flow=16 L x min(-1), width=10 ms) were generated by a jet-generator consisting of a solenoid valve and an injector, situated between pneumotachograph and outflow resistance. Serially arranged resistance-inertance-compliance (R-I-C) lung models (RM=1.3-6.4 kPa x L(-1) x s, CM=7.4-36.9 mL x kPa(-1), IM=1.5 Pa x L(-1) x s2) were used to measure the real and imaginary part of Zrs between 4 and 50 Hz and to determine R, C and I by means of the method of least squares. The median errors for R, C and I were -0.1 kPa x L(-1) x s (-2%), 2.4 mL x kPa(-1)(13%) and -0.2 Pa x L(-1) x s2 (-13%) for measurements without breathing signals and 0.11 kPa x L(-1) -s (3%), 3 mL x kPa(-1) (16%) and 0.28 Pa x L (-1) x s2 (19%) in mechanically ventilated models. During spontaneous breathing the influence of the breathing flow on Zrs was negligible. The equipment did not show any nonlinearity when different pulse amplitudes were used (Vmax=13-22 L x min(-1)). The investigations have shown that jet-pulses allow reliable measurements of respiratory impedance and have the potential to provide valuable information about lung mechanics in spontaneously breathing and mechanically ventilated newborns. The developed measuring head has a low apparatus dead space, is easy to disinfect, has standard connections and can be used as the T-piece in a ventilator circuit.

Effects of a multiple mild infra-red-A induced hyperthermia on central and peripheral pulse waves in hypertensive patients

The paper reports on the effects of multiple whole-body infra-red-A irradiational (IRA) on 13 male patients known to have stage I or stage II essential arterial hypertension (WHO definition). The peripheral blood pressure was decreased significantly by IRA exposures. The lowered diastolic blood pressure lasted into post-treatment time. This effect is regarded as a consequence of an improvement in peripheral haemodynamics. A measure of this improvement is the different shape of the blood pressure pulse waves. Calculation and comparison of the spectral components of the recorded pulse signals show that these components are useful for a prediction of the blood pressure lowering effect.

Modelluntersuchungen zur Bestimmung der Inertance des respiratorischen Systems bei beatmeten Neugeborenen mit Jet-Impulsen

Die Forced Oscillation Technique (FOT) ist ein mitarbeitsunabhangiges, nichtinvasives Verfahren zur Untersuchung der Atemmechanik und auch fur Neugeborene interessant. Eine Miniaturisierung der Mestechnik ist durch Einsatz von Jet-Impulsen moglich. Die FOT ermoglicht die Bestimmung der Inertance des respiratorischen Systems, die bei maschineller Beatmung wegen der hohen Volumenbeschleunigung wie auch bei krankheitsbedingten Flussigkeitseinlagerungen in der Lunge klinisch relevant ist. Die Messung der Inertance eroffnet bei Neugeborenen neue diagnostische Moglichkeiten fur die Atemfunktionsdiagnostik unter Beatmung sowie bei der Surfactant-Therapie oder Partial-Liquid Ventilation.

Therapiebewertung in der Dermatologie durch farbmetrische Vergleichsmessungen

Für erste Untersuchungen ist wegen der besonderen Eignung das Blutschwämmchen (blastomatöses Hämangiom, lat: Haemangioma cavernosum sive capillare, engl.: strawbeny mark) ausgewählt worden. Es handelt sich dabei um eine gutartige Gefäßgeschwulst, die aus massenhaft vermehrten kleinen Blutgefäßen besteht Bis zu 10% aller Kinder weisen ein solches Blutschwämmchen au£ was besorgte Eltern zum Hautoder Kinderarzt führt. Im kinderdennatologischen Patientengut steht es häufig an erster Stelle [1]. Man unterscheidet oberflächliche (kutane) und in die Tiefe reichende (kutan-subkutane) Hämangiome. Die oberflächlichen Blutschwämmchen bilden sich bis zum 6. Lebensjahr in 92% der Fälle spontan zurück, die tieferen aber nur zu 44%. Der Anteil der Spontanheilungen steigt bis zum 12. Lebensjahr nur leicht auf 55% [2].

Modelluntersuchungen zur Impulsoszillometrie bei Neugeborenen

EINLEITUNG: Obwohl oszillatorische Verfahren zur Untersuchung der Atemmechanik schon frühzeitig bei Neugeborenen eingesetzt wurden [6], befinden sich diese Verfahren für Neugeborene und Säuglinge wegen verschiedener technischer Schwierigkeiten (z.B. Applikation des Testsignals) noch heute in der Entwicklung, und es ist keine kommerzielle Meßtechnik für diese Altersgruppe verfügbar. Deshalb fand die klinische Anwendung oszillometrischer Verfahren bisher keine große Verbreitung, obwohl sie verschiedene Voneile besitzen (z.B. nichtinväsiv, keine Kooperation des Patienten erforderlich, auch bei pulmonalen Inhomogenitäten einsetzbar). Für Erwachsene und Kleinkinder ist dagegen bereits ein kommerzielles Gerät (MasterScreen IOS, Fa. Jaeger/ Würzburg) zur Bestimmung der respiratorischen Impedanz auf Basis der Impulsoszillometrie (IOS) erhältlich, mit dem bisher Kinder bis zu 2 Jahren untersucht wurden [2]. Die Verwendung von Impulsen [2,4,5] eröffnet im Gegensatz zu polyfrequenten periodischen Testsignalen [1,6] neue meßtechnische Möglichkeiten (hohe Zeitauflösung, Miniaturisierung des Impulsgebers). Da aber eine direkte Portierung der für Erwachsene entwickelten Methoden nicht möglich ist, sollte untersucht werden, ob sich Jet-Impulse als Testsignal für die • Bestimmung der respiratorischen Impedanz bei Neugeborenen eignen.