Ketone monoester intake affects the ventilatory response to O(2) and CO(2) in healthy individuals at high altitude

In this double-blind, placebo-controlled study, 34 participants completed a normoxic session and a hypobaric hypoxic session after 20 hours at 3,375 m, with regular ketone ester or placebo drinks during the altitude session only. Ketone ester intake increased blood beta-hydroxybutyrate and reduced blood pH, arterial CO2 partial pressure and bicarbonate. It induced hyperventilation and reduced the ventilatory response to O2 and CO2, an effect the authors attribute most likely to hyperventilation while breathing ambient air. Ketone ester did not affect middle cerebral artery velocity or cerebrovascular reactivity.