When the air hits your brain: Cerebral autoregulation of brain oxygenation during aerobic exercise allows transient hyperoxygenation: Case report

OBJECTIVE: Cerebral autoregulation maintains a relatively stable cerebral blood flow over a range of perfusion pressures. During exercise, regional cerebral blood flow may be elevated in particular areas of the brain. This case report presents the impact of aerobic exercise on intracranially measured pressure and brain tissue oxygenation in an adult human. CLINCIAL PRESENTATION: A 30-year-old man with idiopathic intracranial hypertension treated with cerebrospinal fluid diversion was monitored with a Licox intracranial brain oxygen and pressure monitor (Integra NeuroSciences Corporation, Plainsboro, New Jersey) for refractory nonpostural headaches exacerbated after exercise. He performed trials of running and bicycling to provoke his headaches. The patient's mean intracranial pressure remained stable during exercise despite elevated cerebral perfusion pressures. Regional cerebral oxygen tension levels were strictly regulated to a level of approximately 39 mm Hg during steady state aerobic exercise, with transient increases up to 90 mm Hg at the onset and termination of activity. CONCLUSION: Our results suggest that cerebral autoregulation appears to maintain constant cerebral oxygen tension during exercise. Further, we note transient cerebral hyperoxygenation at the onset of exercise as autoregulation "turns on" and at the termination of exercise. We present a quantitative interpretation of the post-exercise hyperoxygenation phase based on Fick's principle. We are the first to demonstrate cortical hyperoxygenation in a human breathing natural air without oxygen supplementation.