ABSTRACT
Respiratory alkalosis is the acid-base disturbance characterized by a primary decrease in the carbon dioxide tension (PCO2) of the body fluids, i.e., by primary hypocapnia. The decrease in PCO2 has an alkalinizing effect on body fluids, but the magnitude of alkalinization is ameliorated by secondary decrements in plasma [HCO3
] that occur by two mechanisms (extra-renal and renal). Acutely (within minutes) hypocapnia elicits a modest decrement in plasma [HCO3
] due to extra-renal mechanisms; no further significant changes in plasma acid-base composition occur for several hours, thus establishing an ‘‘acute steady state.’’ When hypocapnia persists for a longer period of time, however, renal acid excretion is appreciably decreased, resulting in a further reduction in plasma [HCO3
] that further ameliorates the impact of hypocapnia on blood pH. Nevertheless, this adjustment falls short of returning blood [Hþ] completely to its preexisting or normal value.
