Functional reserves of the human body as assessed by Doppler sonography

A study was performed to find informative functional tests for assessing cerebrovascular reactivity. The effects of the hypoxic (breathing a gas mixture containing 10% O2), closed-loop rebreathing, voluntary hyperventilation, and Stange and Hench tests on the cerebral blood flow were compared. Doppler sonography was used to determine the linear velocity of the blood flow in the middle cerebral artery without imaging the vascular lumen. The hyperventilation and closed-loop rebreathing tests caused significant changes in the calculated vasomotor activity (-48 and +61%, respectively). A combination of these two tests can be used as a clinical test for cerebrovascular reactivity. © MAIK Nauka 2008.