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Physics - Physiology - Radiology and Medical Imaging


Effect of Hyperoxia and Hypercapnia on Tissue Oxygen and Perfusion Response in the Normal Liver and Kidney
Published: Friday, July 06, 2012
Author: Hai-Ling Margaret Cheng

by Hai-Ling Margaret Cheng

Objective

Inhalation of air with altered levels of oxygen and carbon dioxide to manipulate tissue oxygenation and perfusion has both therapeutic and diagnostic value. These physiological responses can be measured non-invasively with magnetic resonance (MR) relaxation times. However, interpreting MR measurements is not straight-forward in extra-cranial organs where gas challenge studies have only begun to emerge. Inconsistent results have been reported on MR, likely because different organs respond differently. The objective of this study was to elucidate organ-specific physiological responses to gas challenge underlying MR measurements by investigating oxygenation and perfusion changes in the normal liver and kidney cortex.

Materials and Methods

Gas challenges (100% O2, 10% CO2, and carbogen [90% O2+10% CO2]) interleaved with room air was delivered to rabbits to investigate their effect on tissue oxygenation and perfusion. Real-time fiber-optic measurements of absolute oxygen and relative blood flow were made in the liver and kidney cortex.

Results

Only the liver demonstrated a vasodilatory response to CO2. Perfusion changes to other gases were minimal in both organs. Tissue oxygenation measurements showed the liver responding only when CO2 was present and the kidney only when O2 was present.

Conclusion

This study reveals distinct physiological response mechanisms to gas challenge in the liver and kidney. The detailed characterization of organ-specific responses is critical to improving our understanding and interpretation of MR measurements in various body organs, and will help broaden the application of MR for non-invasive studies of gas challenges.

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