STUDY OBJECTIVE: To examine the effects of targeted inspiratory muscle training on respiratory muscle function, clinical ratings of dyspnea, and perception of resistive loads in symptomatic patients with chronic obstructive pulmonary disease.
DESIGN: Randomized, placebo-controlled trial with an 8-week treatment period.
SETTING: Outpatient pulmonary clinic and pulmonary function laboratory.
PARTICIPANTS: We studied 19 patients with moderate to severe chronic obstructive pulmonary disease, assigning 10 patients to an experimental group and 9 to a control group.
INTERVENTIONS: Patients in both groups trained for 15 minutes twice each day using a device that provided breath-to-breath visual feedback of training intensity. Patients in the experimental group trained at six increasing levels of inspiratory resistance, whereas the patients in the control group trained at a constant, nominal level of resistance.
MEASUREMENTS AND RESULTS: Although there was no statistically discernible difference in the effects of targeted muscle training on the mean difference in maximal inspiratory pressures between the two groups (9.83 cm H2O; 95% CI, -7.37 to 27.03), patients in the experimental group did show a significant increase in inspiratory muscle strength (15.03 cm H2O; P = 0.01). Experimental subjects also had decreased dyspnea after 8 weeks of training compared with control subjects (P = 0.003). Improvements in physiologic values and in dyspnea ratings were correlated. The perception of added resistive loads was not affected by inspiratory muscle training.
CONCLUSIONS: Targeted inspiratory muscle training may enhance respiratory muscle function and reduce dyspnea in symptomatic patients with moderate to severe chronic obstructive pulmonary disease.
PMID: 2742247 DOI: 10.7326/0003-4819-111-2-117

Nocturnal desaturations during rapid eye movement (REM) sleep, caused by nonobstructive hypoventilation, occur frequently in patients with chronic obstructive pulmonary disease (COPD). This is partly caused by decreased activity of the intercostal and accessory muscles due to a lower motor command. The diaphragm has to compensate for the diminished activity of these muscles during REM sleep. However, in patients with COPD strength and endurance of the diaphragm may be affected by its unfavorable position on the length-tension curve because of hyperinflation. The aim of this study was to establish the causal relationship between respiratory muscle function and nocturnal saturation in patients with COPD. We hypothesized that target-flow inspiratory muscle training (TF-IMT) would improve nocturnal saturation. In 20 patients with stable COPD (FEV1 35.5 +/- 14.1% of predicted) and a mean nocturnal saturation below 92% we measured maximal inspiratory pressure (PImax), transdiaphragmatic pressure (Pdi), maximal sustainable inspiratory pressure (SIPmax), endurance time, and nocturnal saturation in Weeks 0, 4, and 10. During these 10 wk 10 patients underwent TF-IMT at 60% of PImax and 10 control patients received sham TF-IMT at 10% of PImax. PImax, Pdi, SIPmax, and the endurance time as well as the nocturnal saturation improved significantly in the 60% training group (by 3.0 +/- 1.5 kPa, 3.4 +/- 1.9 kPa, 1.5 +/- 1.4 kPa, 189 +/- 149 s, and 1.9 +/- 2.2%, respectively), whereas no changes occurred in the sham training group. Also, significant correlations were observed between the changes in Pdi, SIPmax, and endurance time on the one hand and the change in nocturnal saturation on the other. We conclude that TF-IMT improves the nocturnal saturation in patients with severe COPD by increasing respiratory muscle strength and endurance.
PMID: 8542126 DOI: 10.1164/ajrccm.153.1.8542126

The aim of the present study was to investigate the effects of an interval-based high-intensity inspiratory muscle training (H-IMT) programme on inspiratory muscle function, exercise capacity, dyspnoea and health-related quality of life (QoL) in subjects with chronic obstructive pulmonary disease. A double-blind randomised controlled trial was performed. Sixteen subjects (11 males, mean forced expiratory volume in one second (FEV(1)) 37.4+/-12.5%) underwent H-IMT performed at the highest tolerable inspiratory threshold load (increasing to 101% of baseline maximum inspiratory pressure). Seventeen subjects (11 males, mean FEV(1 )36.5+/-11.5%) underwent sham inspiratory muscle training (S-IMT) at 10% of maximum inspiratory pressure. Training took place three times a week for 8 weeks and was fully supervised. Pre- and post-training measurements of lung function, maximum inspiratory pressure, maximum threshold pressure, exercise capacity, dyspnoea and QoL (Chronic Respiratory Disease Questionnaire; CRDQ) were obtained. H-IMT increased maximum inspiratory pressure by 29%, maximum threshold pressure by 56%, 6-min walk distance by 27 m, and improved dyspnoea and fatigue (CRDQ) by 1.4 and 0.9 points per item, respectively. These changes were significantly greater than any seen following S-IMT. In conclusion, high-intensity inspiratory muscle training improves inspiratory muscle function in subjects with moderate-to-severe chronic obstructive pulmonary disease, yielding meaningful reductions in dyspnoea and fatigue.
PMID: 16772388 DOI: 10.1183/09031936.06.00105205

OBJECTIVE: To evaluate the ability of patients with chronic obstructive pulmonary disease (COPD) to accomplish 6 weeks of inspiratory muscle training (IMT) using a pressure threshold device, and to observe how the training affected inspiratory muscle strength and dyspnea.
DESIGN: Pilot study comparing baseline values with posttest values.
SUBJECTS: Four adults with severe COPD (the mean of the forced expiratory volume in 1 second [FEV1] was 28% of predicted value).
METHODS: Daily IMT sessions of 5 to 30 minutes' duration and weekly training load increments of -2 to -4cmH2O over a 6-week period with the training device at loads of >30% of baseline maximal inspiratory pressure (PImax).
OUTCOME MEASURES: Dyspnea measures were Mahler's Baseline and Transition Dyspnea Index and the Borg category-ratio scale administered during a submaximal exercise protocol.
RESULTS: All subjects tolerated the training load, improved their inspiratory muscle strength, and reported reduced dyspnea.
CONCLUSION: Using a constant-load pressure threshold device to attain loads of >30% of the patient's baseline PImax is a feasible way to accomplish inspiratory muscle training in adults with severe COPD.
PMID: 9915380 DOI: 10.1016/s0003-9993(99)90315-5

Six patients with severe chronic obstructive pulmonary disease underwent a six-week outpatient program to train their respiratory muscles with an inspiratory resistive device. Exercise performance was measured using a cycle ergometer. Maximum exercise capacity, represented by VO2 max, increased 15 percent. The maximum work rate increased 37 percent, and the minute ventilation attained during exercise increased 17 percent after training. Respiratory muscle endurance increased 56 percent. All patients reported an increased ability to perform the activities of daily living. No changes were reported in three patients who underwent sham training.
PMID: 6950876 DOI: 10.1378/chest.81.4.436