Experimental studies on microcirculation under normobaric hyperoxia using the microspheres method

Effects of ventilation with 100% oxygen during early hyperdynamic porcine fecal peritonitis*

“…This redistribution of cardiac output in favor of the hepatosplanchnic organs, which confirms previous findings in rodents (11,30), may assume particular importance: Up to now, no vasoactive drug had increased hepatosplanchnic blood flow beyond its effect on cardiac output (34). Using laser Doppler flowmetry, we did not observe any change in microvascular blood flow during oxygen ventilation, which is in contrast to findings in healthy, anesthetized pigs using microsphere techniques (35). Since tissue PO 2 values were also comparable, it is unlikely that we missed major microvascular effects.…”

Imaging the changes in renal T1 induced by the inhalation of pure oxygen: A feasibility study

“…The results described here do not provide strict evidence that the T 1 shortening upon pure oxygen inhalation is only due to the direct relaxation effect of oxygen. However, considering that the inhalation time was restricted to around 5 min, the only physiological parameter that could significantly change during that interval is blood flow (18). Long hyperoxia periods (hours) may produce changes in activity of antioxidant enzymes, in sodium excretion, or in mitochondrial function (23, 24).…”

“…While it is well known that cerebral perfusion is little affected by hyperoxia (16), studies on tumors have shown that hyperoxia produces a vasoconstrictive effect on blood vessels which causes a reduction in blood flow (17); hence, the widespread use of carbogen (5% CO 2 , 95% O 2 ) in tumor studies where improved oxygenation is required. Several experimental and clinical studies demonstrated an increase of renal perfusion after oxygen exposure: in micropigs using radioactively labeled microspheres, a significant increase in renal perfusion was found after 4–6 hr of hypoxia (18), and in normal volunteers and renal transplant patients, hypoxia induced a decrease in renovascular resistance as measured by Doppler (19). Since an eventual vasodilatation could explain the effect of an increase in the levels of dissolved oxygen in the blood, an attempt was made to determine if such an effect was present with the dynamic sequence used in this study.…”

Quantitative tissue oxygen measurement in multiple organs using 19F MRI in a rat model

“…Despite many attempts, animal studies have generally failed to identify specific organs or tissue areas of altered blood flow during hyperoxia. An increase in vascular resistance from hyperoxia has been observed in animal models, but blood flow to major organs appeared to be preserved (27–29). The specific mechanisms of both changes in vascular resistance and changes in tissue oxygen consumption remain unknown, leaving the regional effects of hyperoxia unclear, and highlighting the need for direct tissue oxygen measurement.…”