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High-intensity Inspiratory Muscle Training in Patients With Chronic Obstructive Pulmonary Disease and Severely Reduced Function

Covey, Margaret K. PhD; Larson, Janet L. PhD; Wirtz, Scott E. BS; Berry, Jean K. PhD; Pogue, Nancy J. PhD; Alex, Charles G. MD; Patel, Minu MSc

Journal of Cardiopulmonary Rehabilitation: July-August 2001 - Volume 21 - Issue 4 - p 231-240

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 (PI max ) and increased as tolerated to 60% of PI max . Dependent variables were measured before and after 4 months of IMT: inspiratory muscle strength (PI max ), 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, PI max increased from 64 ± 15 to 75 ± 17 cm H 2 O (P < .05), performance on the DC-ITL test increased from a maximal load of 37 ± 12 to 53 ± 13 cm H 2 O (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.

From the University of Illinois at Chicago, College of Nursing, Chicago, Ill (Drs Covey, Larson, Berry, and Pogue, Mr Wirtz, and Mr Patel); Hines VA Hospital, Division of Pulmonary and Critical Care Medicine, Hines, Ill and Loyola University Chicago, Stritch School of Medicine, Maywood, Ill (Dr Alex).

This study was supported by a grant from the National Institutes of Nursing Research, grant number NRO1428; and was conducted at the University of Illinois at Chicago, College of Nursing, Chicago, Ill and Hines VA Hospital, Section of Critical Care and Pulmonary Medicine, Hines, Ill.

Address correspondence and reprint requests to: Margaret K. Covey, PhD, University of Illinois at Chicago, College of Nursing, 845 South Damen Avenue, Chicago, IL 60612 (e-mail:

© 2001 Lippincott Williams & Wilkins, Inc.