High-intensity inspiratory muscle training in patients with chronic obstructive pulmonary disease and severely reduced function.

PURPOSE: This study examined the effects of inspiratory muscle training (IMT) with high-intensity inspiratory pressure loads on respiratory muscle performance and exertional dyspnea. METHODS: This was a randomized single-blind clinical trial. Twenty-seven patients with chronic obstructive pulmonary disease (18 men, 9 women) with severe to very severe airflow obstruction and severely limited functional performance were assigned randomly to an IMT group (n = 12) or an educational control group (n = 15). The IMT group trained with a threshold loaded device for 30 minutes a day for 16 weeks using interval training techniques. Training was initiated with inspiratory pressure loads equal to 30% of maximal inspiratory pressure (Plmax) and increased as tolerated to 60% of Plmax. Dependent variables were measured before and after 4 months of IMT: inspiratory muscle strength (Plmax), respiratory muscle endurance (discontinuous incremental threshold loading test [DC-ITL]), dyspnea (Chronic Respiratory Disease Questionnaire [CRQ]), and the Borg Category-Ratio Scale ratings of perceived breathing difficulty (RPBD) at equal loads during the DC-ITL. RESULTS: In the IMT group, Plmax increased from 64 +/- 15 to 75 +/- 17 cm H2O (P < .05), performance on the DC-ITL test increased from a maximal load of 37 +/- 12 to 53 +/- 13 cm H2O (P < .05), RPBD decreased from 5.5 +/- 2.5 to 3.8 +/- 2.6 for equal loads on the DC-ITL (P < .05) and the CRQ Dyspnea Scale improved from 18.1 +/- 5.1 to 22.4 +/- 5.2 (P < .05). CONCLUSIONS: Inspiratory muscle training at high-intensity loads significantly improved inspiratory muscle strength, respiratory muscle endurance, and respiratory symptoms during daily activities and respiratory exertion.

Reliability of submaximal exercise tests in patients with COPD. Chronic obstructive pulmonary disease.

UNLABELLED: Submaximal constant work rate exercise tests are often used to measure the efficacy of an exercise intervention, but the reliability of these tests in patients with chronic obstructive pulmonary disease (COPD) has not been established. PURPOSE: To examine the reproducibility of submaximal exercise responses of COPD patients compared with those of healthy elderly subjects. METHODS: Sixteen COPD patients and 15 healthy subjects performed four weekly submaximal exercise tests against two different constant work rates: 20 W and 50% of the peak work rate (PWR). Spirometry was performed before each exercise test. COPD patients and healthy subjects were: age 69 +/- 5 and 65 +/- 5 yr, body mass index 26.4 +/- 3.9 and 26.7 +/- 3.0 kg x m(-2), respectively. RESULTS: Both groups had no change in minute ventilation (V(E)), oxygen uptake (VO2), breathlessness (RPB), and leg fatigue (RPLF) for either work rate over repeated measures (P > 0.05). At 50% PWR test-retest reliability coefficients for V(E) and VO2 ranged from r = 0.88 to r = 0.96 for COPD patients and from r = 0.72 to r = 0.97 for healthy subjects; for RPB and RPLF test-retest reliability ranged from r = 0.76 to r = 0.89 for COPD patients and from r = 0.70 to r = 0.91 for healthy subjects. Intrasubject mean absolute differences for repeated measures of V(E), VO2, RPB, or RPLF were low and there were no group differences (P > 0.05). Percent error for V(E) and VO2 ranged from 6 +/- 3 to 9 +/- 7%, and for RPB and RPLF ranged from 19 +/- 18 to 68 +/- 65% for both groups at each work rate. CONCLUSIONS: Submaximal exercise responses were reliable over a 1-month period, and measures of the physiological and psychophysical responses of COPD patients were as reliable as those of healthy subjects.

Cycle ergometer and inspiratory muscle training in chronic obstructive pulmonary disease.

In patients with chronic obstructive pulmonary disease (COPD) the intensity of aerobic training is limited by dyspnea. Improving strength of the inspiratory muscles could enhance aerobic exercise training by reducing exercise-related dyspnea. We examined effects of home-based inspiratory muscle training (IMT) and cycle ergometry training (CET) in 53 patients with moderate to severe COPD (FEV(1)% pred, 50 +/- 17 [mean +/- SD]). Patients were randomly assigned to 4 mo of training in one of four groups: IMT, CET, CET + IMT, or health education (ED). Patients were encouraged to train to the limits of their dyspnea. Inspiratory muscle strength and endurance increased in IMT and CET + IMT groups compared with CET and ED groups (p < 0. 01). Peak oxygen uptake increased and heart rate, minute ventilation, dyspnea, and leg fatigue decreased at submaximal work rates in the CET and CET + IMT groups compared with the IMT and ED groups (p < 0. 01). There were no differences between the CET and CET + IMT groups. Home-based CET produced a physiological training effect and reduced exercise-related symptoms while IMT increased respiratory muscle strength and endurance. The combination of CET and IMT did not produce additional benefits in exercise performance and exercise-related symptoms. This is the first study to demonstrate a physiological training effect with home-based exercise training.

Test-retest reliability of symptom-limited cycle ergometer tests in patients with chronic obstructive pulmonary disease.

BACKGROUND: Symptom-limited exercise tests are widely used to evaluate the effects of pulmonary rehabilitation in patients with chronic obstructive pulmonary disease (COPD), but the reliability of these tests is not well established in COPD patients. OBJECTIVES: We compared test-retest reliability of two repeated symptom-limited exercise tests between COPD patients and healthy elderly subjects and between male and female patients. METHOD: Fifty-six COPD patients (40 men, 16 women) and 16 healthy subjects (6 men, 10 women) performed two symptom-limited exercise tests approximately 2 weeks apart. Measures of oxygen uptake (VO2), minute ventilation (VE), heart rate, and ratings of breathlessness and leg fatigue were obtained at peak exercise at each symptom-limited exercise test. RESULTS: Repeated measures of peak exercise responses were stable for patients and healthy subjects and for male and female patients. Although mean percent error (absolute difference/mean) for peak exercise responses was low, some individuals' values exceeded 10%. There was no difference in the percent error between COPD patients and healthy subjects or between men and women with COPD. Test-retest reliability was lower for breathlessness ratings than for other peak exercise responses for all groups. CONCLUSIONS: Repeated symptom-limited exercise tests are reliable in COPD patients and healthy subjects. However, some individuals are less reliable, and these patients may require more than one exercise test to establish reliable performance.

Discontinuous incremental threshold loading test: measure of respiratory muscle endurance in patients with COPD.

STUDY OBJECTIVE: To assess the discontinuous incremental threshold loading (DC-ITL) test as a measure of respiratory muscle endurance for patients with COPD in terms of perceived breathing difficulty, reliability, and validity. DESIGN: The DC-ITL test was repeated three times at weekly intervals under identical test conditions. SETTING: Clinical research laboratory. PATIENTS: Forty-eight patients with moderate to severe COPD. MEASUREMENTS AND RESULTS: Rating of perceived breathing difficulty (RPBD) was measured at the end of each stage of the DC-ITL test with a Borg category-ratio scale. The maximal inspiratory pressure (PImax) was measured before and after the DC-ITL test. Breathing patterns were measured during the DC-ITL test. The mean (+/-SD) for RPBD at the maximal load was 6.3 (3.1), 6.6 (2.8), and 6.7 (2.7) for visits one, two, and three, respectively (not significant). The mean relative maximal load for the DC-ITL test (peak mouth pressure as a percent of PImax) at the last completed stage was 59+/-23%, 62+/-20%, and 63+/-19% for visits one, two, and three, respectively (not significant). Test-retest reliability was r1,2=0.82 and r2,3=0.69 for relative maximal load and r1,2=0.90 and r2,3=0.90 for absolute maximal load (peak mouth pressure). Tidal volume decreased (p < 0.01) and respiratory rate increased (p < 0.01) from the next-to-the-last to the last completed stage. PImax decreased after the DC-ITL test (p < 0.01). CONCLUSIONS: Moderate breathing difficulty was experienced during the DC-ITL test. The test was reliable and the results of this study support its validity as a measure of respiratory muscle endurance.

Reliability and validity of the functional performance inventory in patients with moderate to severe chronic obstructive pulmonary disease.

The Functional Performance inventory (FPI) is a new instrument designed to measure functional status in terms of activities that people perform on a daily basis. Psychometric characteristics were examined by a survey of 45 men and 27 women with chronic obstructive pulmonary disease (COPD). Internal consistency reliability was high and no ceiling and floor effects were observed for the Total FPI. Concurrent validity was demonstrated by correlations with the Total Sickness Impact Profile (r = -.59). Construct validity was supported by correlations with the Medical Outcomes Study Short Form-36, Physical Functioning (r = .69), the Physical Activity Scale for the Elderly (r = .62) and American Thoracic Society-Division of Lung Disease Breathlessness scale (r = -.62). The Total FPI is a reliable and valid measure of functional performance in persons with COPD.

Reliability and validity of the 12-minute distance walk in patients with chronic obstructive pulmonary disease.

Validity and test-retest liability of the 12-minute distance (12MD) walk, a measure of functional status, were examined in patients with chronic obstructive pulmonary disease. Four tests were administered at weekly intervals. Performance increased (p < .01) over the first three tests. Test-retest reliability was r34 = .98 (df = 46) for tests 3 and 4. The 12MD walk correlated with the Sickness Impact Profile, Physical Dimension (r = -.45); forced expiratory volume in 1 second % predicted ( r = .40); maximal inspiratory pressure (PImax) (r = .52); and exercise-related breathlessness (r = -.49). Exercise-related breathlessness and PImax accounted for 42% of the variance. The validity and reliability of the 12MD walk were supported.

Inspiratory muscle training in patients with chronic obstructive pulmonary disease.

The effects of 6 months of muscle training with an inspiratory pressure load equal to 30% of the maximal inspiratory pressure (PImax) was compared with sham training with a light inspiratory pressure load. In this double-blind randomly assigned study, 67 patients with chronic obstructive pulmonary disease were followed for 6 months. Both groups demonstrated improvements in performance of PImax, respiratory muscle endurance time for breathing against an inspiratory pressure load equal to 66% of PImax, 12-minute distance walk, and dyspnea. The treatment group did not demonstrate significant effects beyond those observed in the control group. Improvements in performance were related to improved coordination of the inspiratory muscles and desensitization to dyspnea.

Maximal inspiratory pressure. Learning effect and test-retest reliability in patients with chronic obstructive pulmonary disease.

Reliability of the maximal inspiratory pressure (Pimax) was examined by measuring Pimax once a week for 4 weeks in 91 patients with chronic obstructive pulmonary disease using an aneroid pressure gauge. Five Pimax trials were conducted at each test. From the first to the fourth test, the Pimax increased by a mean of 9 cm H2O (SD = 10). From the third to the fourth test, Pimax increased by a mean of 2 cm H2O and performance appeared to be plateauing. The test-retest reliability coefficient was r = 0.97 for Pimax measured at the third and fourth test session. The 95 percent confidence interval for the absolute difference in Pimax at the third and fourth test was 3 to 5 cm H2O. We conclude that performance of Pimax improves with practice in naive COPD patients and Pimax is reliable when measured with an aneroid gauge by experienced data collectors if patients are given sufficient practice.