Figure 36-20 The effect of sodium bicarbonate administration on end-tidal PCO₂ . A continuous tracing of end-tidal PCO₂ is shown as a function of time. Intravenous administration of 50 mEq followed by 30 mEq of NaHCO₃ results in an abrupt increase in expired CO₂ because of neutralization of bicarbonate by hydrogen ions.