Effects of sodium bicarbonate on voluntary face immersion breath-hold times

The purpose of this study was to examine the effects of orally ingested sodium bicarbonate (NaHCO3) on voluntary breath-hold time with facial immersion. Eight non-elite breath-hold divers aged 20-41 (26.75 +/- 7.83 years) were recruited to undertake two bouts of three monitored, facial-immersion breath-holds, one week apart. Subjects were randomly allocated to double-blind sessions of ingesting an experimental (0.3 g x kg(-1) NaHCO3) or placebo (8 g NaCl) solution. Heart rate, pre- and post-breath-hold end-tidal gases, peripheral oxygen saturation (SpO2) at right index finger and maximum breath-hold times (Max-BHT) were recorded. Max-BHT was established during the third breath-hold in both trials. Max-BHT of 168.2 (+/- 20.7) sec and 145.7 (+/- 21.4) see were recorded for the experimental and placebo conditions, respectively (P = 0.019). Average bradycardic response did not differ between the experimental and placebo trials (P = 0.166). Whilst there was a significant difference in post-breath-hold end-tidal oxygen (P(ET) O2), one was not noted in end-tidal carbon dioxide (P(ET) CO2) measures (P = 0.048, and; P = 0.530, respectively). There was significant difference in lowest recorded SpO2 (P = 0.008) between the trials. It is suggested that ingestion of NaHCO3, prior to facially immersed breath-holds, has an ergogenic effect, prolonging Max-BHT by approximately 8.6%.