Figure 2.

Overall death risk through the Cox proportional hazards models. In box plot (a), the Cox model includes only VE/VCO₂ slope, in box plot (b), the Cox model includes VO₂ peak/kg, and in box plot (c), the Cox model includes VO₂ peak/kg + DLCO%. A bidirectional stepwise model selection method minimizing the Bayesian information criterion (BIC) was utilized for selecting the optimal model which was identified as VO₂ peak/kg + DLCO%. Data are described using standard box plots with medians (interquartile range). Risk was found to be significantly differentiated between dead and alive with P = 0.0028, P = 0.008, and P < 0.0001, respectively.