Figure 3
Relationships between measured maximum O 2 transport (VO 2 ), y-axis; and, estimated cellular oxygenation (PmO 2 ), x-axis, in COPD patients. The different symbols correspond to classical GOLD stages: squares, GOLD II; circles GOLD III; and, triangles, GOLD IV (measured VO2 obtained from [32]). The symbols connected with discontinuous lines correspond to the same patient (same VO2) with estimated PmO2 values corresponding to different mitochondrial oxidative capacities (Vmax values and VO2/Vmax ratios). For a given patient, the lower the VO2/Vmax ratio, the lower was the estimated PmO2. The colors correspond to the mitochondrial ROS generation: green, mitochondrial ROS levels similar to those seen in healthy subjects; red, abnormally high mitochondrial ROS levels; and, violet, high ROS levels that persist after exercise withdrawal. The lower the PmO2, the higher were mitochondrial ROS levels.