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Biomedical subjects

S Odman

Publications and source records attributed to S Odman.

33 records · Page 2Linked to original sources
PubMed1985

A multiwire surface oxygen pressure electrode for measurement across zones of normal and damaged tissue.

The standard MDO multiwire surface oxygen electrode was redesigned to enable measurements across transition zones between normal and, e.g., ischemic tissues. The eight measuring points were arranged in an array 2.2 mm long. This array multiwire electrode (AME) has been tested and showed the same electrochemical properties as the standard MDO electrode. The resolving power was tested and an individual measuring point was affected by a change in surrounding pO2 if it occurred within a distance of 20 microns. In experiments in the pig heart subjected to local ischemia it was found that both ischemic and normal tissue oxygen pressure were registered simultaneously by the AME.

Animals↗
PubMed1985

Characterization of subcutaneous edema by mechanical impedance measurements.

The mechanical behavior of gels of various water content, normal and edematous tissues have been studied. Static deformations and vibrations at low frequencies were applied to an area of each of these structures. Softer structures, e.g., gel containing a high percentage of water and pitting edema, have lower mechanical impedance (MI), while harder structures, e.g., nonpitting edema have higher MI. A comparison of the static force measured at bilateral sites on normal subjects show lower differences in impedance than do similar comparisons made in subjects having unilateral edema. This difference is more pronounced with greater static compression. The differences in the MI between different structures are greater at the lower frequencies. At the lower frequencies up to around 30 Hz the ratio of the magnitude of MI of edematous skin and that of contralateral normal skin can indicate the degree of edema. The MI of edematous tissues depends on the type of edema and varies with its degree. Thus this study introduces a quantitative method for the diagnostic and therapeutic assessment of unilateral subcutaneous edema.

Adult↗
PubMed1985

Locally applied 133Xenon for the measurement of regional cerebral blood flow (rCBF): an experimental study in the pig.

A method for measuring regional cerebral blood flow has been developed. On pig brain cortex a 1 cm2 size polyester film was placed, under which 0.6-1.3 mCi of 133Xenon in 2-4 microliter of saline was applied atraumatically. The wash-out process was registered with an external detector, and can be described as a sum of monoexponential functions. The first component of the curve, obtained by curve resolution, indicates blood flow in grey matter and the second slow component indicates blood flow in white matter. When total ischaemia was induced, there was no wash-out of the isotope. Freezing the brain after isotope application at different stages during the wash-out showed isotope in both grey and white matter. The isotope did not diffuse into the polyester film. This technique was also used in studies on the spinal medulla where white matter is outermost and grey innermost. The wash-out curve obtained consisted of only one monoexponential function; blood flow from grey matter was not present in the wash-out curve. For calculation of cerebral blood flow a modified two-compartment model was used. It is concluded that this method measures local cerebral blood flow in both grey and white matter. The method can be used clinically to measure the local cerebral blood flow during neurosurgical operations.

Animals↗
PubMed1984

Morphology of endoneurial blood vessels of frog sciatic nerve during vascular perfusion.

In order to determine if increased injection pressures can alter the permeability and ultrastructure of blood vessels of the frog blood-nerve barrier, these vessels were examined following perfusion of the iliac artery at rates of 0.21 or 0.82 ml/min. At either perfusion rate, endoneurial blood vessel profiles were clearly evident and the surface area of these vessels amounted to 60% of the surface area of the perineurium. In all vessels a large number of vesicles were present within the endothelial cells. Many were attached by necks to one or the other plasma membrane, but no transcellular channels were evident. At the higher flow rate no changes in vesicles or junctions were seen, but blebs and blisters were evident at the luminal membranes of the endoneurial endothelium. When microperoxidase was perfused at 0.82 ml/min, reaction product frequently flooded the endothelial cells, was found as clumps on the cell surface, and was distributed within the endoneurial space. These changes represent the only ultrastructural evidence of endothelial cell damage and altered permeability in response to increased rate of perfusion.

Animals↗
PubMed1980

Skeletal muscle oxygen pressure fields in rats. A study of the normal state and the effects of local anesthetics, local trauma and hemorrhage.

The MDO (Mehrdraht Dortmund Oberfläche) oxygen electrode was used for studies of oxygen pressure fields in rat skeletal muscle. With this multiwire oxygen electrode, the three-dimensional oxygen pressure field was measured and presented as a two-dimensional frequency distribution, i.e., a histogram. Statistical analysis of the histograms was carried out with the two-sample Kolmogorov-Smirnov test. This eliminated the influence of mean values, since these do not always represent the actual biological situation. The oxygen pressure fields in skeletal muscle of anesthetized normal rats breathing air spontaneously were investigated. When the oxygen pressure in the inspired gas was changed (50% and 95%), changes were seen in muscle oxygen pressure curves. The normal oxygen pressure field histograms were compared with those obtained after local anesthesia, after local trauma to the muscle and after hemorrhage. After local anesthesia the histograms were unchanged. Significant changes in the distribution types of the histograms were found after trauma in all rats studied. After hemorrhage significant changes, similar to those seen after trauma, were found in 15 of the 23 rats studied. Local blood flow was also measured with the 133xenon-clearance method in the hemorrhage experiments. No correlation was found between the changes in the mean oxygen tension values and the changes in 133xenon-clearance.

Animals↗
PubMed1980

Data acquisition and information processing in MDO oxygen electrode measurement of tissue oxygen pressure.

In 1956, CLARK presented the principle for the modern, membrane-covered, oxygen electrode, comprising the anode and the cathode within the same unit. A further development was the MDO (Mehrdraht Dortmund Oberfläche) oxygen electrode presented by LUBBERS & KESSLER during the 1960s. This electrode comprises eight separate measuring points for collecting statistical samples to calculate tissue oxygen pressure fields. In order to perform studies on humans and to enable fast presentation of measurement results, a system was developed including a PDP 11/03 D computer, which fulfils patient safety demands. The computer program included corrections for electrode drift and temperature influences, as well as statistical calculations including mean, standard deviation, skewness and kurtosis. Also included was the two-sample Kolmogorov-Smirnov test for comparison of tissue oxygen distributions. Experience from studies on humans has shown that the measurement system enables us to collect and read important patient data directly at the bedside in the intensive care ward.

Computers↗
PubMed1980

A technique for disinfection of the MDO oxygen electrode.

A method for disinfection and aseptic assembly of the MDO (Mehrdraht Dortmund Oberfläche) oxygen electrode has been evaluated. The method is based on treating each electrode component separately and then assembling the different parts under aseptic surgical conditions. The performance of the disinfected electrode was studied and found to be unchanged as compared with a non-disinfected electrode. Bacteriological studies on the effectiveness of the disinfection technique described and on the permeability of the electrode membranes to bacteria and bacterial spores were performed. The electrode membranes were penetrated by bacteria in experiments simulating in-use conditions in about 11% of membranes tested, after contamination of the inner electrode surface with heavy inocula. When studies were performed with the disinfected MDO oxygen electrode on humans, routine cultures from the wound were positive in about 10% of the cases. No clinical wound infection was seen. The majority of the positive cultures were probably caused by the surgical technique rather than the handling of the electrode. The disinfection method for the MDO oxygen electrode described in this paper makes it possible to use the electrode clinically, except in cases of hepatitis.

Bacterial Infections↗
PubMed1980

Skeletal muscle oxygen pressure fields in artificially ventilated, critically ill patients.

The MDO (Mehrdraht Dortmund oberfläche) oxygen electrode was used in a study of skeletal muscle oxygen pressure fields, presented as histograms, in critically ill patients artificially ventilated with gas mixtures of different oxygen concentrations. The histograms were compared with forearm blood flow measurements performed with strain gauge plethysmography. Local blood flow and permeability-surface area product (PS) were also studied by the simultaneous clearances of 133xenon and 51Cr-EDTA. The histogram distribution type was normal, i.e. approximately Gaussian, at arterial oxygen pressure levels between 10 and 18 kPa. At arterial oxygen pressures outside this range the histogram distribution types were abnormal, i.e. they showed a non-symmetrical distribution of oxygen pressure values, but their mean was approximately the same as in the normal histogram. However, there were significantly higher tissue oxygen pressure mean values in the patients (3.43 kPa) than in a group of healthy human volunteers (2.25 kPa). Mean forearm blood flow and the clearances of 133xenon and 51Cr-EDTA showed marked variations during the measurements both intraindividually and interindividually. Mean forearm blood flow and mean clearances of 133xenon showed opposite trends compared with arterial oxygen pressures. Mean clearances of 51Cr--EDTA and means PS showed only minor variations at the different arterial oxygen pressure levels.

Adult↗
PubMed1979

ECG electrodes. A study of electrical and mechanical long-term properties.

The long-term properties of commercially available ECG-electrodes were studied by investigating the parameters: polarization potential, electrical impedance, adhesion, and skin reactions during a period of 7 days. As expected, the most stable polarization potentials were obtained for Ag/AgCl electrodes. Certain simple disposable electrodes showed large polarization potential variations. The most stable electrode impedance was obtained for disposable electrodes with stable adhesion and equipped with an electrode cup or similar. Unchanged adhesion and mechanical properties during the test period were shown by the disposable electrodes with a large self-adhesive collar.

Adhesiveness↗