FIGURE 2.

Typical calculation of muscle oxygen saturation index (%StiO₂) during a loaded breathing set. Baseline %StiO₂ (defined as the average of the last 10 s before the initiation of each breathing set), Mean %StiO₂ (defined as the average of the last two breaths of each set) and Nadir %StiO₂ (defined as the lowest value recorded during the last two breaths of each set). Numbers (from 1 to 8) represent the number of breaths of the set. %StiO₂ data depict the sternocleidomastoid muscle. %StiO2 changes from baseline are calculated as follow: Mean-Baseline = −3.8% and Nadir– Baseline = −6.3%.