Fig. 3

Relationship between \( \dot{V}_{{{\text{O}}_{ 2} }} \) and \( \dot{V}_{\text{CO}} \) (upper panel) and between \( \dot{V}_{\text{E}} \) and \( \dot{V}_{\text{CO}} \) (lower panel) obtained during the ramp exercise period on 8 non-smokers. Note that the relationship between \( \dot{V}_{{{\text{O}}_{ 2} }} \) and \( \dot{V}_{\text{CO}} \) appears to be linear, but the relationship between \( \dot{V}_{\text{E}} \) and \( \dot{V}_{\text{CO}} \) appears to be curvilinear. The pattern of the changes among subjects was very similar