Figure 4 Scatter plot of slope a for the two devices. ( A ) Scatter plot of slope a in patients with COPD. ( B ) Scatter plot of slope a in non-COPD subjects. Abbreviations : slope a, Borg scores vs percentage of oral pressure from the patient’s maximum; COPD, chronic obstructive pulmonary disease; I-TLD, hand-held electronic incremental threshold loading device; C-TLD, traditional threshold loading device.