Biomedical subjects

S Koteng

Publications and source records attributed to S Koteng.

4 recordsLinked to original sources

PubMed2003

Decompression profile and bubble formation after dives with surface decompression: experimental support for a dual phase model of decompression.

The present study was initiated in order to determine the effect of decompression profiles on bubble formation following surface decompression using oxygen. Following an air dive to 496 kPa (130 fsw) for 90 minutes, three different profiles were tested in the pig; a USN staged decompression profile, a profile using linear continuous decompression with the same total decompression time as the USN profile (ABI) and a linear profile with half the total decompression time compared to the the first two (ABII). The subsequent surface decompression at 220 kPa lasted 68 minutes for all three schedules. The study demonstrated that, following final decompression, the two linear profiles produced the lowest amount of vascular gas, with the fastest profile producing significantly less bubbles in the Pulmonary artery than the other two. Similar results were obtained in the jugular vein. The results are in qualitative agreement with model simulation using the Reduced Gradient Bubble Model (RGBM), demonstrating that the controlling tissues are reduced from those with a half time of 40 minutes using the USN procedure to 5 minutes using the fastest linear profile.

Animals↗

PubMed2002

Microdialysis in cisterna magna during cerebral air embolism in swine.

Arterial gas embolism may occur as a consequence of lung rupture, decompression sickness, following operative procedures or as accidental infusion of gas during various diagnostic procedures. It can lead to severe morbidity or even death. Microdialysis is a technique that has been extensively used for evaluating localized changes in the brain. The microdialysis probe is only capable of measuring changes in the immediate adjacent tissue. In arterial gas embolism the changes are multifocal. Thus a probe located in the cerebral cortex will not detect the total amount of damage. We used microdialysis in the cisterna magna of 9 anaesthetized pigs to study the diffuse injury following arterial gas embolism. After injection of 5.0 mL of air in the internal carotid artery, we found a significantly increased lactate-pyruvate ratio in the cerebrospinal fluid, lasting for 2 hours. This indicates anaerobic metabolism. Mean levels of glycerol were significantly increased, indicating membrane disruption. Glutamate levels were also elevated, although not significantly. The injection of air affected carotid flow. Flow in the carotid artery of the side of injection decreased significantly, but returned to baseline in 1 hour. Flow in the contralateral carotid was increased, but not significantly. We conclude that massive air embolism causes ischemia and reduced blood flow in the brain that can be detected in the cisterna magna.

Animals↗

PubMed1999

Endothelial damage by bubbles in the pulmonary artery of the pig.

A method for measuring endothelial damage caused by decompression was developed for vessels with a large radius. Segments of the pulmonary artery from pigs (8-12 wk old) were tested for endothelium damage using a system for recording changes in the tension in the vessel wall. Substance P (SP) was used as an endothelial-dependent dilation agonist. A significant decrease was found in the total response (Tmax) for SP as a result of endothelium damage, and the reduction in response was related to the number of bubbles. Furthermore, the sensitivity of the vessels to the agonist was significantly reduced after exposure to bubbles. Staining the endothelium with silver nitrate and light microscopy confirmed mechanical endothelium damage.

Animals↗

PubMed1998

Effect of oxygen tension and rate of pressure reduction during decompression on central gas bubbles.

Reduction in ascent speed and an increase in the O2 tension in the inspired air have been used to reduce the risk for decompression sickness. It has previously been reported that decompression speed and O2 partial pressure are linearly related for human decompressions from saturation hyperbaric exposures. The constant of proportionality K (K = rate/partial pressure of inspired O2) indicates the incidence of decompression sickness. The present study investigated the relationship among decompression rate, partial pressure of inspired O2, and the number of central gas bubbles after a 3-h dive to 500 kPa while breathing nitrox with an O2 content of 35 kPa. We used transesophageal ultrasonic scanning to determine the number of bubbles in the pulmonary artery of pigs. The results show that, for a given level of decompression stress, decompression rate and O2 tension in the inspired air can be traded off against each other by using pulmonary artery bubbles as an end point. The results also seem to confirm that decompressions that have a high K value are more stressful.

Animals↗