Figure 3. Panel A. The ventilatory equivalents for oxygen (V̇E/V̇O2) and carbon dioxide (V̇E/V̇CO2). V̇O2θ¸, the first threshold, is identified by the dual criteria of a systematic increase in V̇E/V̇O2 without an increase in V̇E/V̇CO2. V̇O2θ¸, the second threshold, is identified by a systematic increase in V̇E/V̇CO2. Panel B. End-tidal gas tensions for oxygen (PETO2) and carbon dioxide (PETCO2). V̇O2θ¸, the first threshold, corresponds with the requirement that PETO2 systematically increases while PETCO2 does not decrease. Note that V̇O2θ¸ is identified at V̇O2 = 1.40 L/min. V̇O2θ¸, the second threshold, corresponds with the requirement that PETCO2 systematically decreases.
