Bicarbonate Infusion Attenuates Arterial Desaturation During Maximal Exercise

Maximal exercise is associated with a reduced O 2 saturation of arterial haemoglobin (SaO 2 ). We evaluated the effect of pH in the reduction of SaO 2 during maximal exercise by attenuating the metabolic acidosis with intravenous administration of bicarbonate. Eight competitive oarsmen (age 22.5 ± 3 yr, body weight 78 ± 2 kg, and height 1.83 ± 0.05 m; mean ± SD) performed 2000 m maximal ergometer row in random order either with sodium bicarbonate (Bicarb, 100 to 325 ml; 1 mM) or an equal volume of 0.9% saline (Sal). Arterial blood samples were obtained at rest and immediately after exercise. During the Sal trial arterial pH was reduced to 7.12 ± 0.01, while during Bicarb acidosis was attenuated in a dose related manner (7.29 ± 0.03; P <0.05). Lactate concentration during Bicarb was higher than Sal (26 ± 3 vs. 20 ± 1 mM; P <0.05). Also, bicarbonate concentration and SaO 2 were higher (20.5 ± 1.8 mM vs 11.8 ± 0.8 mM and 92.5 ± 1% vs 89.4 ± 1%; P <0.05) during Bicarb compared to Sal, respectively. Arterial O 2 partial pressure decreased similarly during the two trials (82.5 ± 2.6 vs. 87.3 ± 2.1 mmHg). The results demonstrate that during maximal exercise the decrease in SaO 2 is influenced not only by the limited pulmonary diffusion capacity but also by the attenuated O 2 affinity for hemoglobin induced by the decrease of plasma pH (Bohr effect). Support or Funding Information Dr. Per Bredmose received a grant from The Købmand i Odense Johann og Hanne Weimann f. Seedorfs foundation.