Inspiratory muscle training in chronic airflow limitation: Comparison of two different training loads with a threshold device

Abstract

The usefulness of inspiratory muscle training (IMT) in chronic airflow limitation (CAL) patients is a controversial issue, mainly due to differences in the training load. To further evaluate this aspect, we studied the effect of the magnitude of the load using a threshold pressure trainer. Ten CAL patients (5 males, 5 females), 67±2 yrs (mean±SEM) and forced expiratory volume in one second (FEV1) 36±2% pred, 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 trained using only 12% of their PImax (Group 2). Training was assessed by PImax, inspiratory muscle power output (IMPO), sustainable inspiratory pressure (SIP), maximal inspiratory flow rate (V̇Imax), pattern of breathing during loaded breathing, Mahler's dyspnoea score, and the 6 min walking distance (6MWD). After 5 weeks of training, Group 1 exhibited significant increments in: PImax (34±11%); IMPO (92±16%); SIP (36±9%); and V̇Imax (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 increment in tidal volume (VT) and mean inspiratory flow (VT/TI), and a reduction in inspiratory time (TI). In Group 2, VT and VT/TI also increased significantly, but the breathing frequency increased with a reduction of expiratory time. When comparing both groups after training, significant differences in PImax, IMPO, V̇Imax and dyspnoea were observed, with no significant changes in the other parameters. We conclude that, in patients with chronic airflow limitation, inspiratory muscle training with a high enough load improves inspiratory muscle strength and power output, reduces dyspnoea, and makes the pattern of breathing adequate during loaded breathing. These changes may allow patients to cope better with increased loads imposed by physical effort and exacerbation of symptoms.