Fig. 5
From: Lung hyperinflation in COPD: applying physiology to clinical practice
Tidal volume (VT), breathing frequency (F b), dynamic inspiratory capacity (IC) and inspiratory reserve volume (IRV) are shown plotted against minute ventilation (/\( \dot{\mathrm{V}} \)E) during constant work rate exercise for each forced expiratory volume in 1Â s (FEV1, expressed as % predicted) quartile (Q). The upper through to lower quartiles (Q1-Q4) represent the mildest to most severe groups, respectively. Note the clear inflection (plateau) in the VT//\( \dot{\mathrm{V}} \) E relationship which coincides with a simultaneous inflection in the IRV. After this point, further increases in \( \dot{\mathrm{V}} \)E are accomplished by accelerating F b. Data plotted are mean values at steady-state rest, isotime (i.e., 2Â min, 4Â min), the VT//\( \dot{\mathrm{V}} \)E inflection point and peak exercise. (Modified from: [29])