ABSTRACT
The effect of high altitude upon CBF, appearing simple at first, has proved complex. With acute ascent to about 4000 m altitude, cerebral blood flow (CBF) rises by 3060%. Over the next few days to weeks it falls, and after months to years it is not different from sea level normal values, despite chronic severe hypoxemia. This fall is not due to insensitivity to hypoxia because in natives of altitude, CBF falls in response to acute hyperoxia. There is no evidence of decreased cerebral metabolic rate for oxygen (CMRo2), which remains normal even in hypoxia severe enough to obtund consciousness and increase brain lactic acid. In this chapter we examine the physiological responses of cerebral circulation to short-and long-term hypoxia.
