VASCULAR REACTIVITY IN MIDDLE CEREBRAL-ARTERY AND BASILAR ARTERY BY TRANSCRANIAL DOPPLER IN NORMALS SUBJECTS DURING HYPOXIA

The anatomical and physiological differences between the carotid and v ertebrobasilar circulations suggest the possibility of a different res ponse to variations in systemic pO(2). We evaluated cerebrovascular re sponse (CR) in these two systems by monitoring variations in the blood flow velocities in the middle cerebral and basilar arteries during hyp oxia. Eighteen healthy, non-smoking volunteers under-went transcranial Doppler study during a state of hypoxia obtained by means of the rebr eathing method. Oxyhaemoglobin saturation (SaO(2)) was monitored using a pulsoxymeter in the 88-94% range. The cerebral blood flow velocity (BFV) was measured in the right middle cerebral artery (MCA) and the b asilar artery (BA). Our findings indicate that the mean bloodflow velo city (MFV) in the BA changes at a lower rate than that in the MCA duri ng hypoxia.