FIGURE 2.

End‐tidal CO₂ (${\text{ET}}_{{\text{CO}}_2}$) measured at 1‐min intervals during gas exposure (means ± SD). ${\text{ET}}_{{\text{CO}}_2}$ correlates with concentration of CO₂ in the inhaled gas mixture. Note that each group reaches ${\text{ET}}_{{\text{CO}}_2}$ steady state at 1 min