Effect of low oxygen inhalation on changes in blood pH, lactate, and ammonia due to exercise

Abstract

The present study examined the effect of hypoxia-induced respiratory alkalosis on exercise-induced metabolic acidosis and increases in plasma lactate and ammonia levels. Six male subjects underwent exercise of increasing intensity until exhaustion: (1) in normoxia (20.9% O(2)) (=MAX), (2) in hypoxia (12% O(2)) (=HP) in which hypoxic condition had been maintained from 60 min before to 30 min after exercise, and (3) the same intensity of exercise as HP in normoxia (=SUB). Arterialized blood was drawn from a superficial vein. Post-exercise blood pH was significantly higher in HP than in MAX ( P<0.05), although plasma lactate was at the same level. For hypoxia as compared to normoxia, regression analysis confirmed a parallel shift of plasma lactate to higher pH levels indicating the effect of respiratory alkalosis ( P<0.01). After exercise plasma levels of ammonia were lower in HP than in MAX ( P<0.05). Regression analysis between ammonia and pH revealed nearly identical changes in hypoxia and normoxia at low pH. From these results, we conclude that: (1) hypoxia-induced respiratory alkalosis attenuated exhaustive exercise-induced metabolic acidosis, (2) plasma lactate concentration was determined by the relative exercise intensity, (3) the maximum plasma ammonia concentration under exhaustive exercise was reduced at hypoxia because of respiratory alkalosis.

Effects of Hypoxia on the Onset of Muscle Deoxygenation and the Lactate Threshold

“…Grassi et al [3] hypothesized that during graded exercise in normoxia, the increased acidemia that occurred at the LT was responsible for the OMD because of a Bohr effect on the oxy-hemoglobin dissociation relationship. However, it is difficult to rationalize this mechanism to explain the concurrent leftward shifts in the LT and OMD observed in the current study because recent studies have reported that blood pH was higher under hypoxic than normoxic conditions during submaximal [9] and maximal [10] exercise. The higher blood pH was attributed to a hypoxic-induced respiratory alkalosis, even though blood lactate concentrations at the end of maximal exercise were similar under both conditions [10].…”

“…However, it is difficult to rationalize this mechanism to explain the concurrent leftward shifts in the LT and OMD observed in the current study because recent studies have reported that blood pH was higher under hypoxic than normoxic conditions during submaximal [9] and maximal [10] exercise. The higher blood pH was attributed to a hypoxic-induced respiratory alkalosis, even though blood lactate concentrations at the end of maximal exercise were similar under both conditions [10]. In summary, we observed a concurrent leftward shift in the LT and OMD during hypoxia; however the mechanism to explain this phenomenon warrants further investigation.…”

Effects of Gas Exchange on Acid‐Base Balance

“…At the level of skeletal muscle, in contrast to what occurs with induced MALK (117), the induction of a respiratory alkalosis by hyperventilation resulted in a slowed activation of skeletal muscle pyruvate dehydrogenase (PDH) at the onset (1 min) of submaximal exercise, which resulted in an increased accumulation of pyruvate within contracting skeletal muscle (165 When a respiratory alkalosis is induced by breathing a hypoxic gas mixture, the acid-base and metabolic changes differ markedly from a strictly hyperventilation induced respiratory alkalosis. Kato et al (148) induced a respiratory alkalosis in six subjects by having them breathe a hypoxic gas mixture of 12% O 2 for 60 min prior to exercise onset and for up to 30 min of postexercise recovery. When at rest, plasma pH increased from 7.401 to 7.437 (not significant) while [HCO 3 − ] increased significantly from 24.0 to 27.2 mmol/L (Fig.…”

Effect of hypercapnia on changes in blood pH, plasma lactate and ammonia due to exercise

“…Previous studies suggested that hypoxia-induced respiratory alkalosis enhances lactate accumulation in blood by exercise (Davies et al 1986;Kato et al 2004;LeBlanc et al 2002). LeBlanc et al (2002) demonstrated PFK activity to be enhanced by respiratory alkalosis and suggested that respiratory alkalosis due to hyperventilation potentiates lactate accumulation.…”