Search PubMed⌕ Search

Biomedical subjects

R Schosser

Publications and source records attributed to R Schosser.

30 records · Page 2Linked to original sources
PubMed1980

The effect of PEEP ventilation on hemodynamics and regional blood flow with special regard to coronary blood flow.

An experimental study was performed to evaluate the effects of positive end-expiratory pressure (PEEP) on central hemodynamics and on regional blood flow (RBF) using the radioactive microsphere (MS) method. Ten dogs with intact lungs and 10 dogs with oleic acid-induced pulmonary edema were ventilated with PEEP 10 and PEEP 20 (cmH2O). PEEP significantly reduced cardiac output (CO) by 25% at PEEP 10 and 40--50% at PEEP 20 despite volume expansion with dextran 60. RV afterload rose markedly due to a significant increase of pulmonary vascular resistance. PEEP tended to redistribute CO in favor of brain, heart and adrenals, at the expense of stomach, pancreas and thyroid glands. Hepatic artery flow was moderately reduced; renal RBF was seriously affected only when PEEP caused an extreme low-output state. RBF to the RV remained essentially unchanged, whereas RBF to the LV decreased, roughly paralleling the respective ventricular work. Nevertheless, the RV may suffer from underperfusion during PEEP, since its tension-time-index rises; this may indicate increased oxygen needs exceeding actual oxygen delivery.

Adrenal Glands↗
PubMed1980

[Regional blood flow in splanchnic organs during positive end-expiratory pressure ventilation (author's transl)].

An experimental study was performed on 10 dogs to evaluate the effect of positive end-expiratory pressure ventilation (PEEP) on hemodynamics and regional blood flow (RBF). The following conclusions can be drawn from the results of this study: 1) PEEP leads to a significant reduction of cardiac output (CO). 2) Total blood flow to the preportal splanchnic organs, and consequently the portal venous flow, decreases in proportion to the reduction of CO. Within the splanchnic area, there is a redistribution of RBF in favour of the small and large intestines, at the expense of stomach and pancreas. 3) The arterial blood flow to the liver is only moderately affected. 4) The observed changes of RBF may in part contribute to the complications of the splanchnic organs occurring in PEEP-ventilated patients. 5) PEEP should be used only when strictly indicated; close monitoring of organ function appears mandatory in these patients.

Animals↗
PubMed1979

MIC-II - a program for the determination of cardiac output, arterio-venous shunt and regional blood flow using the radioactive microsphere method.

MIC-II is a versatile BASIC computer program designed to calculate the cardiac output, the arterio-venous shunt and the regional blood flow from data obtained by the radioactive microsphere method. The samples are measured in a gammaspectrometer with a multichannel pulse height analyzer and the data are recorded on tape. Up to 10 different nuclides may be used simultaneously, including tracers which are not bound to microspheres. The nuclides may have overlapping energy spectra. The analysis of the energy spectra is performed according to the matrix method. Standard samples, each containing one pure nuclide, are measured to obtained the overlap matrix. The unkown amounts of the nuclides in the samples are obtained by solving a system of simultaneous linear equations. Up to 100 organ samples may be taken in one experiment. Up to 10 different organ maps, containing a text label for each organ specimen, may be created, edited, modified and stored on tape for convenient identification of input and output. Numerous validity checks for imput and output make MIC-II easy to use, even for non-computer trained personel.

Animals↗
PubMedDate not supplied

Open chest and open pericardium affect the distribution of myocardial blood flow in the right ventricle.

We have investigated the effects of open chest and open pericardium on the distribution of myocardial blood flow assessed with the radioactive microsphere technique (15 microns). Five dogs with intact thorax served as controls (group I) and six dogs were studied after a right-sided thoracotomy and pericardiotomy (group II). Global myocardial blood flow (mean +/- S.D.) was 0.73 +/- 0.17 ml.min-1.g-1 in group I and 1.22 +/- 0.09 ml.min-1.g-1 in group II (p less than 0.05). Analysis of transmural blood flow distribution revealed that flow was 44% higher in the right and 60% higher in the left ventricular endocardial layers in the open-chest animals, whereas epicardial flow increased by 105% and 90%, respectively. As a result of the preferential blood flow to the epicardial layers of the right ventricle, the endo/epi ratio was reduced from 1.30 +/- 0.26 in group I to 0.86 +/- 0.11 in the open-chest group (p less than 0.05). Left ventricular endo/epi ratio was 1.27 +/- 0.16 and 1.06 +/- 0.11 (n.s.), respectively. External work and diastolic filling pressure of the right ventricle did not differ between the two groups and therefore cannot account for the redistribution of myocardial blood flow. It is concluded that the distribution of myocardial blood flow, particularly in the RV, is severely disturbed by thoracotomy and pericardiotomy. This is an important aspect for the planning and evaluation of studies under open-chest/open-pericardium conditions.

Animals↗
PubMedDate not supplied

A comparison of JPEG and FIF compression of color medical images for dermatology.

Dermatologists were shown digitized images of skin lesions compressed by Joint Photographic Expert Group (JPEG) and fractal image format (FIF) algorithms and asked to make a diagnostic assessment and rate the image quality in displaying the features necessary for that assessment. Dermatologists performance in the diagnostic assessment was not affected by the level of compression (up to 40X) using either algorithm, but ratings of image quality for all compressed images were significantly lower than for uncompressed images and for the original photographic slides. There were no significant differences in dermatologists' performance or ratings between the two compression algorithms.

Algorithms↗
PubMedDate not supplied

Risk/benefit evaluation of drugs: the role of the pharmaceutical industry in Germany.

Drugs that are efficacious have usually also undesired side effects. When applying for marketing authorization of a drug, demonstration of a positive risk/benefit ratio is a prerequisite for approval by the competent authorities. Once on the market, risk/benefit evaluation has to be continued in order to determine whether the risk/benefit ratio is still positive or not. The German Drug Law, by means of article 5, poses this responsibility on the pharmaceutical entrepreneur. Specific instructions on how to perform the risk/benefit evaluation can be derived from article 5, and a decision matrix was developed to support taking action if the risk/benefit ratio has changed. Historical and current examples are presented to illustrate changes of the risk/benefit ratio, problems associated with detecting risk signals, and the resulting regulatory actions.

Drug Industry↗
PubMedDate not supplied

Evaluation of ibuprofen for pressure ulcer prevention: application of a rat pressure ulcer model.

This blinded study describes the effect of ibuprofen (IBU) on experimental pressure ulcers (PU) induced in the fuzzy rat model. Ibuprofen's fibrinolytic activity has been found effective in preserving dermal vasculature in rats following burn injury. Experimental pressure ulcers were generated on the hips of fuzzy rats with the aid of computer control, using five daily, 6-hour pressure sessions. In the first study, 17 rats received intraperitoneal (I.P.) injection of IBU or saline control after each pressure session. In the second study, 44 rats received IBU or control, before, during, and after application of pressure by I.P. or intramuscular (I.M.) injections. Quantitation of histology is based on five prominent lesions, including: ulceration, infarction, panniculus carnosus necrosis, fat atrophy, and deep muscle necrosis. The following hypothesis was tested: Reperfusion injury and vascular occlusion in pressure ulcers may be similar to that which occurs in burns and, therefore, is responsive to IBU intervention. The results indicate that IBU does not have significant effects on the development of pressure ulcers. The mechanisms of IBU action in other organ and tissue systems are discussed in relation to the effect of IBU on the pressure ulcer model.

Animals↗