Pathophysiology of the vasomotor reactivity to hypo- and hypercapnia: role of aging and chronic cerebrovascular disorders.

Cerebrovascular CO2 reactivity was studied in 40 healthy subjects (HSs) and 40 patients suffering from cerebrovascular disorders (CVD). Transcranial Doppler (TCD) sonography was used to investigate MCA flow velocity modifications during PaCO2 changes induced by ventilatory rate modifications and closed-circuit air re-breathing. HS responses were correlated with age, whereas the roles of either multiple ischemic brain lesions or carotid occlusions were studied in the Pt group. Results were as follows: i) age did not prove to affect vasomotor response to PaCO2 variations; ii) in hypercapnia, patients with multifocal ischemic lesions showed an impaired response in both hemispheres, whereas altered vasoreactivity was unilateral in patients with carotid occlusion (and ipsilateral to the thrombosis); iii) no significant differences were found between HS and Pt responses in hypocapnia. These findings confirm previous reports obtained with the 133 Xenon technique, stressing the usefulness of cerebrovascular reactivity investigation in CVD pts for diagnostic and prognostic purposes.