Fig. 1.

Grouped data comparing the eupneic end-tidal CO₂ (A) and eupneic V̇e (B) in the 2 age groups: young and elderly. The bars represent averaged data for each age group (black bar = young, n = 15; gray bar = elderly age, n = 10). The eupneic $\mathrm{P}\mathrm{E}{\mathrm{T}}_{\mathrm{C}{\mathrm{O}}_{\mathrm{2}}}$ was significantly lower (*P = 0.006), whereas V̇e was significantly higher in the elderly vs. young age groups (#P = 0.01).