Effect of induced acute metabolic alkalosis on the V̇ E /V̇CO 2 response to exercise in healthy adults

We tested the hypothesis that increasing the respiratory control systems’ arterial PCO 2 equilibrium point via induced acute metabolic alkalosis by ingestion of sodium bicarbonate (NaHCO 3, 0.3 g/kg) would decrease the ventilatory equivalent for CO 2 (V̇ E /V̇CO 2 ) at its lowest point (“nadir”) during constant-load cycle exercise testing performed at 80 % of peak power output in 18 healthy young adults. Compared to the sodium chloride (4 g) control condition, ingestion of NaHCO 3 : increased arterialized venous pH, HCO 3 - and PCO 2 at rest by 0.05 ± 0.01 units (mean ± SE), 6.4 ± 0.4 mEq/L and 4.3 ± 0.7 mmHg, respectively (all p < 0.0001); and decreased the V̇ E /V̇CO 2 nadir during exercise by 9.4 % (p < 0.0001) secondary to a 4.7 ± 1.8 L/min decrease in V̇ E (p = 0.019). In conclusion, induced acute metabolic alkalosis by ingestion of NaHCO 3 decreased the V̇ E /V̇CO 2 response to strenuous exercise in healthy adults.