INSPIRATORY MUSCLE TRAINING IN CHRONIC AIR-FLOW LIMITATION - COMPARISON OF 2 DIFFERENT TRAINING LOADS WITH A THRESHOLD DEVICE

The usefulness of inspiratory muscle training (IMT) in chronic airflow limitation (CAL) patients is a controversial issue, mainly due to dif ferences in the training load. To further evaluate this aspect, we stu died the effect of the magnitude of the load using a threshold pressur e trainer. Ten CAL patients (5 males, 5 females), 67 +/- 2 yrs (mean /- SEM) and forced expiratory volume in one second (FEV1) 36 +/- 2% pr ed, were trained for 30 min a day using a load of 30% of their maximal inspiratory mouth pressure (PImax) (Group 1). Another 10 CAL patients (5 males, 5 females), 73 +/- 2 yrs and FEV1 37 +/- 2% pred), were tra ined using only 12% of their PImax (Group 2). Training was assessed hy PImax, inspiratory muscle power output (IMPO), sustainable inspirator y pressure (SIP), maximal inspiratory flow rate (VImax), pattern of br eathing during loaded breathing, Mahler's dyspnoea score, and the 6 mi n walking distance (6MWD). After 5 weeks of training, Group 1 exhibite d significant increments in: PImax (34 +/- 11%); IMPO (92 +/- 16%); SI P (36 +/- 9%); and VImax (34 +/- 13%). Dyspnoea was also reduced, and the 6MWD increased by 48 +/- 22 m. We observed no significant changes in Group 2. During loaded breathing, Group 1 showed a significant incr ement in tidal volume (VT) and mean inspiratory flow (VT/TI), and a re duction in inspiratory time (TI). In Group 2, VT and VT/TI also increa sed significantly, but the breathing frequency increased with a reduct ion of expiratory time. When comparing both groups after training, sig nificant differences in PImax, IMPO, VImax and dyspnoea were observed, with no significant changes in the other parameters. We conclude that , in patients with chronic airflow limitation, inspiratory muscle trai ning with a high enough load improves inspiratory muscle strength and power output, reduces dyspnoea, and makes the pattern of breathing ade quate during loaded breathing. These changes may allow patients to cop e better with increased loads imposed by physical effort and exacerbat ion of symptoms.