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Biomedical subjects

V Blazek

Publications and source records attributed to V Blazek.

At least 19 recordsLinked to original sources
PubMed1999

Local cold exposure test with a new arterial photoplethysmographic sensor in healthy controls and patients with secondary Raynaud's phenomenon.

Local cold exposure tests are used to diagnose cold-induced vasospastic disorders and to evaluate therapeutic success. We investigated the pulsatile signal detected with a newly developed arterial photoplethysmography (APPG) method and the signal change induced by local cold exposure using a temperature-controlled finger holder, comparing it with laser Doppler flux (red and green laser, rLDF and gLDF) and red blood cell velocity measured in nailfold capillaries (CBV). Ten healthy volunteers and 10 age- and sex-matched patients suffering from Raynaud's phenomenon due to systemic sclerosis were investigated using a moderate cooling temperature of 16 degrees C for 5 min. All signals were recorded simultaneously. The results show a significant reduction of CBV (P < 0.0001), rLDF (P < 0.0003), and gLDF (P = 0.0214) during cooling and characteristic changes in the APPG signal (for instance a decrease in pulse wave amplitude; P < 0.0001). Significant differences in the APPG amplitude could be detected under resting conditions; at cooling temperatures there were also significant differences in CBV and APPG. The temperature-controlled finger holder with its built-in APPG probe appears to be a useful tool for evaluating the effect of local cooling on finger skin perfusion and differentiating between healthy controls and patients with secondary Raynaud's phenomenon due to systemic sclerosis. The gLDF signal was rather weak, limiting its value in cold stress tests. The differences between controls and patients in CBV were somewhat smaller than in previous studies, suggesting the advantage of lower local cooling temperatures, e.g., 12 degrees C.

Adult↗
PubMed1997

[Development of a computer-assisted thermoelectric Peltier cold test procedure with integrated photoplethysmography unit for noninvasive evaluation of acral skin circulation].

Local cold provocation tests are an important, non-invasive diagnostic tool for collecting information about skin perfusion during exposure to cold. In patients suffering from vasospastic circulatory disorders such as Raynaud's phenomenon, it is of particular importance to be able to collect data about acral circulation during the cooling test in the asymptomatic intervals between naturally occurring attacks. By carrying out a series of cold provocation tests, for example, patient response to a newly initiated therapy can be assessed. Here we present a recently developed, computer-aided thermoelectric Peltier device with an integrated finger holder for carrying out local cold provocation tests. The electronic control unit of the Peltier element make it possible to cool or heat to predefined temperatures. At the same time, the temperature of both the finger holder and the skin can be measured. A photoplethysmographic sensor is also integrated within the device, enabling the response of the pulse waves to the controlled temperature changes to be monitored accurately. It is also possible to measure simultaneously laser Doppler flux and capillary pressure in the nailfold and to perform nailfold capillaroscopy to determine red blood cell velocity. The new device provides us with the technical means to study the interrelationship between acral skin perfusion and the thermal regulation of the skin.

Blood Flow Velocity↗
PubMed1996

Attractors and quasi-attractors in the cutaneous perfusion in human subjects and patients: "chaotic" or adaptive behaviour?

The causes of the aperiodic fluctuations in the perfusion of the skin (volar hand, measured by the Laser-Doppler (LD) technique) of healthy human subjects were studied were studied by simultaneous recording of the fluctuations of local blood content (reflectiophotoplethysmography (rPPG)) and those in the skin of the glabella. Various thermoregulatory situations were provoked by exposing 12 subjects to 18, 21, 24 and 27 degrees C ambient temperature; in addition, the hands were placed at, below and above heart level. In mentally relaxed subjects (evidenced by a stable approx. 0.015-Hz rhythm in the glabellar rPPG signal), there was perfect temporal correlation between aperiodic LDA and rPPG signal under all thermoregulatory conditions. Clearly identifiable episodes of retardation associated with skin bleaching, asymmetrical shape of LDA and rPPG signals were taken as indicators of episodic sympathetic skin constrictor (SSC) activity. In synergetic terms, the modulated SSC activity operates as transient "quasi-attractor'. A notable exception occurred: when the hand was placed below heart at 27 degrees C ambient temperature, a sinusoidal periodic fluctuation (approx. 0.03 Hz) in the LDA evolved. These were not seen the rPPG signal, i.e., coherence between LDA and rPPG dynamics was lost). Lack of coherency between LDA-rPPG, also observed in patients with autonomic neuropathy and decompensated forms of peripheral arterial disease, suggesting predominance of spontaneously oscillating myogenic vasomotion after removal of temporally variable SSC drive. Stable vasomotion is regarded as a synergetically stereotyped reaction rather than as "well-ordered' stable attractor mode of operation.

Blood Flow Velocity↗
PubMed1996

A new examination system using photoplethysmography to evaluate skin blood flow during exposure to vibration.

We introduce a new examination method developed at the University Dermatology Hospital in Tübingen in cooperation with the Institute for High Frequency Techniques of Aachen Technical College and the Metabo Factory in Nürtingen, Germany. The Tübingen workplace simulator for studying vibration white finger (VWF) syndrome standardized vibrations reproducing the vibration pattern of actual hand-held tools. This stimulator makes it possible to evaluate on-line the effects of defined vibrations on skin blood flow in the fingers and to investigate the etiopathogenesis of vibration white finger syndrome. The vibration simulator itself is modelled after an altered router with two side-mounted handles. The electronic speed control and exchangeable unbalance pins make it possible to adjust the frequency and amplitude of the vibrations to simulate actual conditions in the job. New developed photoplethysmographic sensors are fastened to the fingertips with double adhesive rings and measure blood flow in the skin. Measurements are recorded simultaneously with a multi-channel plotter. This method is not only useful as a diagnostic tool but has potential future applications in pre-employment screening in the affected industries and in the development of reduced-vibration tools.

Fingers↗
PubMed1994

Toe pressure determination by audiophotoplethysmography.

PURPOSE: The purpose of this study was to evaluate the performance of audiophotoplethysmography as a modality to measure toe pressure without the requirement of a recorder. METHOD: A portable photoplethysmograph with an audio output was used to determine toe pressures, and the results were compared with those obtained by a commercial photoplethysmograph with a recorder. RESULTS: Thirty-one measurements in control subjects and 62 measurements in patients with arterial occlusive disease were performed. The average toe pressure recorded with oscillography with standard photoplethysmography was 103.5 mm Hg +/- 14.7 SD and 95.9 mm Hg +/- 13.4 SD with audio-photoplethysmography. In the patient group the pressure recorded with a commercial photoplethysmograph was 65.3 mm Hg +/- 34.9 SD compared with 61.6 mm Hg +/- 34.8 SD obtained with audio-photoplethysmography. The difference in both groups was insignificant, and the correlation between both methods was very good. CONCLUSION: A portable hand-held photoplethysmograph equipped with an audio output was used to measure toe pressure in control subjects and in patients with arterial occlusive disease. The results have been compared with the oscillometric method by a standard commercial photoplethysmograph connected to a recorder. The correlation was very good in the control and patient groups, and the difference between both methods was below the level of statistical significance. The fact that no recorder is needed may help in introducing toe pressure measurement into everyday office diagnostic practice.

Arterial Occlusive Diseases↗
PubMed1991

[D-SGP Duo--a new plethysmography for acral, arterial and venous blood pressure measurement].

This is to present a new portable plethysmograph using modern microprocessor technology, a two-channel digital strain gauge plethysmograph (D-SGP Duo). This system contains two strain gauges and a pressure gauge and has measuring programmes for thrombosis screening (venous occlusion test) and for the acral blood pressure measurement. For the first time it is possible to determine not only the acral systolic arterial pressure but also the acral venous blood pressure. Examples of application are given.

Blood Pressure↗
PubMed1991

[Computer simulation of the dynamics of the arterial system for various cardiovascular situations].

The simulation model describes the basic characteristics of the pulse in a wide range of arterial vessels. By comparison of simulated stenosis with photoplethysmographic registered curves of patients suffering from stenosis, it could be shown, that also pathologic hemodynamics can be adequately described. A new sight of dicrotic pulse generation was derived by the simulated removal of large arteries. This led to the hypothesis of decoupled, autonomous multiple reflections in the arteries of the arm, the leg and the head.

Arterial Occlusive Diseases↗
PubMed1989

[Laser ablation of the nucleus pulposus: optical properties of degenerated intervertebral disk tissue in the wavelength range 200 to 2200 nm].

Percutaneous ablation of degenerative disk material by laser has been introduced recently as an alternative to enzymatic or mechanical discectomy. The optical properties of degenerative disk material were evaluated in the range from 200 to 2200 nm, which includes most of the laser wavelengths used for medical purposes. Remittance rate was determined in 16 post-mortem disks using a spectrophotometric unit and rate of absorption and scatter were calculated. High rates of diffuse remittance were found for classical laser wavelengths such as the argon or the Nd:YAG II laser indicating only low rates of absorption. In contrast, much higher rates of absorption were determined for excimer or mid-infrared lasers as well as for the Nd:YAG I (1320 nm), which appear more appropriate for laser discectomy than the Nd:YAG (1064 nm) laser.

Humans↗