Objective: The aim of this study was to compare the use of threshold and resistive load devices for inspiratory muscle training in patients with chronic obstructive pulmonary disease (COPD). A randomized prospective trial was designed to compare use of the 2 devices under training or control conditions.
Patients and methods: Thirty-three patients with moderate or severe COPD were randomly assigned to home treatment with a threshold device, a resistive load device, or a control situation in which either of those devices was maintained at a minimum load throughout the study. Training was performed daily in 2 sessions of 15 minutes each for 6 weeks. In the patients who underwent training with threshold (n=12) and resistive load (n=11) devices, the loads used were adjusted weekly until the maximum tolerated load was reached to ensure that the interventions were as equivalent as possible. Respiratory function, respiratory muscle function, and quality of life were assessed before and after training and the different inspiratory pressure profiles were compared between training groups.
Results: Both peak inspiratory pressure and scores on the Chronic Respiratory Questionnaire (CRQ) improved in the groups that received inspiratory muscle training compared with control subjects: maximal static inspiratory pressure increased from 86 cmH2O to 104.25 cmH2O (P< .01) in the threshold device group and from 91.36 cm H2O to 105.7 cmH2O (P< .01) in the resistive load device group. The resistive load group showed the largest increase in CRQ quality-of-life scores. Differences between the dyspnea score on the CRQ at the beginning and end of the training period were as follows: 3 points in the resistive load group, 2.58 in the threshold group, and 2.5 in the control group. Significant differences in duty cycle measured during training sessions were observed between groups at the end of training (0.31 in the threshold group and 0.557 in the resistive load group), but the mean pressure-time index was similar (0.11) in both groups because of the greater peak and mean inspiratory pressures in the threshold device group.
Conclusions: Load readjustment allowed equivalent training intensities to be achieved with different inspiratory pressure profiles. Our study demonstrated the effectiveness of inspiratory muscle training without control of breathing pattern but showed no superiority of one training method over another.