PMC7498836_01
PMC7498836_02
Results of cardiopulmonary testing with incremental load. fR, breathing frequency; IMT, inspiratory muscle training; PETCO2, end-tidal carbon dioxide tension; Ti/Ttot, inspiratory duty cycle; VD/VT, physiologic dead space/tidal volume ratio; V'CO2, carbon dioxide output; V'E, minute ventilation; V'O2, oxygen uptake; VT ex, expiratory tidal volume.
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In both patients, the fR at peak exercise increased (Case 1, from 34/min to 44/min; Case 2, from 34/min to 39/min) (Fig. 1C). Moreover, the expiratory VT (VT ex) at peak exercise decreased in both patients (Fig. 1D), although FEV1 did not change significantly in both patients after IMT (Table 3). V'E/V'CO2 was higher in Case 2 than in Case 1 before IMT throughout the exercise. V'E/V'CO2 increased during exercise in Case 2, but not in Case 1 (Fig. 1E and F). Comparing the exertional patterns of Ti/Ttot and V'E/V'CO2 before IMT with those after IMT, no significant changes were observed in both patients (Fig. 1E and F). IMT seemed not to affect the ventilatory efficiency. In Case 1, furthermore, VD/VT increased slightly and PETCO2 decreased after IMT during exercise (Fig. 1G and H).
Results of cardiopulmonary testing with constant load IMT, inspiratory muscle training.
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In contrast, no change was observed in these measurements in Case 2 (Fig. 2).