Biomedical subjects

N Lund

Publications and source records attributed to N Lund.

76 records · Page 5Linked to original sources

PubMedDate not supplied

Tissue blood exchange and tissue oxygen tension in relation to total body oxygen consumption in experimental surgical shock.

This experimental shock model was well defined by the marked decrease in total body oxygen consumption, muscle PO2 and diffusion capacity during shock. Infusion of large amounts of electrolyte solution did not lead to a restoration of muscle oxygen tension after 1-4 hours. Dextran 40 infusion however restored both local PO2 and blood flow in the muscle as well as total body oxygen consumption.

Animals↗

PubMedDate not supplied

Tissue oxygen pressure in normal myocardium and across the border zone during coronary artery occlusion in the pig. Effects of different arterial oxygen pressures.

Tissue oxygen pressure (ptO2) in the pig heart was measured with two different oxygen electrodes: We measured ptO2 in normal myocardium with the MDO electrode while oxygen gradients across the border zone, during acute coronary artery occlusion, were measured with an array-multiwire-electrode (AME). The aim of the study was to investigate the effects of increased arterial oxygen pressure (paO2) during repeated, short-lasting (5 min) coronary artery occlusions. During ventilation with an inspired oxygen fraction (FIO2) of 0.3 the ptO2 levels in normal myocardium increased significantly, while the distribution type of ptO2 values remained normal. During ventilation with FIO2 0.7 there was an uneven distribution of ptO2 values indicating microcirculatory disturbances, however, no ischemic values were seen. We found no indication for any influence on the ptO2 of the border zone.

Animals↗

PubMedDate not supplied

pH heterogeneity in skeletal muscle extracellular fluid.

Oxygen and carbon dioxide are known to be heterogeneously distributed in tissues. Extracellular skeletal muscle tissue pH (pHt) also exhibits a spatial variability in vitro, but this has not been examined in vivo. pHt distributions in resting skeletal muscle and the effect of the dispersion of pHt on ischemia and normoxic hypercarbia was therefore studied in an animal model with a multichannel pH microelectrode. Under resting conditions and spontaneous breathing, local pHt (from all animals, n = 10) was found to vary between 6.96 and 7.68 (range), and 70% of the values were within a pH of 7.00-7.32. In each animal the maximum pHt differences (maximum range between the 6 channels of the microelectrode) found were 0.32 +/- 0.11 pH units (mean +/- SD). During tissue acidosis, induced by ischemia, no significant change in the local pHt differences in each animal was seen. During normoxic hypercarbia a 2-fold increase in pHt variability within each animal was noticed (p < 0.01), which suggests that carbon dioxide and buffering effects of the blood are significant factors for the pHt distribution. The pHt distribution range found is of similar magnitude as previously described in in vitro studies on skeletal muscle. Locally varying pHt levels may be of importance as they will affect cellular H+ extrusion, membrane potential and volume control of different cell populations differently.

Acidosis↗

PubMedDate not supplied

Oxygen sensitivity of a multichannel antimony microelectrode for tissue surface oxygen pressure measurements.

The measuring properties of antimony electrodes were improved by the introduction of highly purified crystallographically oriented monocrystalline antimony (COMA). COMA electrodes are sensitive to pH and pO2. For measurements of either pH, pO2, or both, the pH and the pO2 sensitivities must be known and the components of the composite electrode signal must be separable. The oxygen sensitivity of COMA electrodes in vivo have been shown to be higher than in vitro in the pO2 range below 10 kPa. The present study was performed in an animal model to investigate the oxygen sensitivity and to further evaluate the tissue pO2 measuring properties of a miniaturized six channel COMA microelectrode. The results show that the COMA microelectrode has negligible drift, a response time of less than 5 s and high sensitivity and reproducibility for tissue pO2 measurements when the pH part of the electrode signal is eliminated. The oxygen sensitivity found (8.5 +/- 0.4 (mV/pO2) (mean +/- SEM)), is described by a direct linear function in the oxygen tension range studied. It is concluded that tissue pO2 can be calculated after elimination of the pH part of the electrode signal. A multichannel COMA microelectrode possess characteristics suitable for in vivo oxygen measurements and is therefore an interesting complement to traditional tissue oxygen sensors.

Animals↗