Fig. 2

Relation between diaphragm and extradiaphragmatic inspiratory muscle activity for pressure support (PS) level 15, 12, 9 and 6 cmH₂O, with peak electrical activity of the diaphragm (EAdi_peak) and peak electromyography (EMG_peak) normalized to muscle activity at PS level 3 cmH₂O (% PS3). Each individual patient is depicted in a specific color and marker. The regression lines describing the relation on individual patient level are depicted, from which the high variability among patients is clear. 3 points are not shown (PS 6 patient 11 for scalene (scalene EMG_peak 298% PS 3 at EAdi_peak 87% PS 3) and PS 12 and 9 patient 14 for sternocleidomastoid (sternocleidomastoid EMG_peak 153 and 386% PS 3 at EAdi_peak 45 and 62% PS 3, respectively), as values were off scale. However, the regression lines shown include these data points