Figure 3

This shows the increase in inspiratory effort for any given tidal volume (VT). The curved arrows indicate the increase in both slope (b) and intercept (a) of the VT to inspiratory effort relationship in patients as compared to healthy subjects. The straight arrows show the progressive increase in dyspnea with increasing b and a (for explanation see text). Abbreviations: MIP = maximal inspiratory pressure; VC = vital capacity; COPD = chronic obstructive pulmonary disease.