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Biomedical subjects

O Hochmuth

Publications and source records attributed to O Hochmuth.

8 recordsLinked to original sources
PubMed2006

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

BACKGROUND: Evaluation of treatments for Raynaud's 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 tau. OBJECTIVES: Here, we describe a novel device termed a duosensor, which records the tau value upon cold challenge in an automated manner. METHODS: We determined tau values in healthy probands, patients with primary or secondary RP associated with autoimmune disease and patients with scleroderma-associated RP following cold challenge, to determine assay variability, sensitivity and specificity. RESULTS: Duosensor-based thermography exhibited low intraindividual variability in healthy probands. As expected, tau values in RP patients were significantly increased compared with controls (8.08 +/- 3.65 min vs. 3.23 +/- 1.65 min). The duosensor-determined tau value yielded a specificity of 94.6% and predictive value of 95.3% for the presence of RP in a retrospective analysis of 139 patients. Furthermore, in a cohort of scleroderma patients with RP, patient self-assessment of RP severity correlated with tau values. CONCLUSIONS: Taken together, the present data suggest that tau value determination provides a suitable outcome measure for clinical studies of novel RP treatments. As the duosensor is a simple stand-alone device requiring no supporting equipment and minimal personnel attention, it should allow RP activity monitoring even in clinical settings with minimal technical infrastructure.

Body Temperature↗
PubMed1999

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.

Airway Resistance↗
PubMed1998

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.

Airway Resistance↗
PubMed1995

[Signal smoothing and differentiation with a single operator].

For the filtering and subsequent processing of of very noisy force curves obtained in studies of isolated heart muscles, an operator derived from the rules used in the construction of Bézier curves has been tested. The advantage of using the latter is that despite major changes in one sample as compared with another, the resulting curve changes only slightly. The derived operator permits either smoothing only or can be extended for both smoothing and differentiation simultaneously. With the filtering operation "smoothing and differentiation", even very noisy signals can be successfully processed. The operator is insensitive to signal interference and has advantages in terms of speed and complexity.

Computer Graphics↗
PubMed1991

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 posttreatment 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.

Adult↗