Fig. 5.

Absolute changes over time in saturation of hemoglobin with oxygen as measured by pulse oximetry oxygen ($\text{S}{\text{p}}_{{\text{O}}_2}$) (A), end-tidal carbon dioxide (EtCO₂) (B), and respiratory rhythm (RR) (C) in case of acute nicotine-vaping (nicotine-session) (red triangles), acute nicotine-free-vaping (nicotine-free-session) (black squares), and acute sham-vaping (stop-session) (blue dots). In comparison to acute sham-vaping, neither acute nicotine-vaping nor nicotine-free-vaping modified $\text{S}{\text{p}}_{{\text{O}}_2}$, EtCO₂, or RR. A mixed-effects linear model analysis was performed with experimental sessions and time points as fixed effects and baseline (BSL) variables as random effects (random intercept model). Data are presented as the mean ± SE.