Medical Director and Sleep Physician Dr Keith R Burgess and Sleep Scientist Katie Colby from Peninsula Sleep Clinic conducted six weeks of high altitude sleep reseacrh at the EV-K2-CNR Pyramid at Lobuche, Nepal in 2012. This paper has been produced from some of the experiments conducted during that trip.
Abstract – Key points
- We investigated the influence of arterial PCO2 (PaCO2) with and without experimentally altered pH on cerebral blood flow (CBF) regulation at sea level and with acclimatization to 5050 m.
- At sea level and high altitude, we assessed stepwise alterations in PaCO2 following metabolic acidosis (via 2 days of oral acetazolamide; ACZ) with and without acute restoration of pH (via intravenous sodium bicarbonate; ACZ+HCO3−).
- Total resting CBF was unchanged between trials at each altitude even though arterial pH and [HCO3−] (i.e. buffering capacity) were effectively altered.
- The cerebrovascular responses to changes in arterial [H+]/pH were consistent with the altered relationship between PaCO2 and [H+]/pH following ACZ at high altitude (i.e. leftward x-intercept shifts).
- Absolute cerebral blood velocity (CBV) and the sensitivity of CBV to PaCO2 was unchanged between trials at high altitude, indicating that CBF is acutely regulated by PaCO2 rather than arterial pH.