Fisioterapia

High-intensity Inspiratory Muscle
Training in Patients With Chronic
Obstructive Pulmonary Disease and
Severely Reduced Function
Margaret K. Covey, PhD; Janet L. Larson, PhD; Scott E. Wirtz, BS; Jean K. Berry, PhD;
Nancy J. Pogue, PhD; Charles G. Alex, MD; Minu Patel, MSc

I PURPOSE: This study examined the effects of inspiratory muscle training
(IMT) with high-intensity inspiratorypressure loads on respiratory
muscle performance and exertional dyspnea.
I 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 (PImax) and increased as tolerated to 60% of PImax. Dependent
variables were measured before and after 4 months of IMT: inspiratory
muscle strength (PImax), respiratorymuscle 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.
I RESULTS: In the IMT group, PImax increased from 64 ± 15 to 75 ± 17 cm
H2O (P .05), performance on the DC-ITL test increased from a
maximalload 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).
I CONCLUSIONS: Inspiratory muscle training at high-intensity loads
significantly improved inspiratory muscle strength, respiratory muscle
endurance, and respiratory symptoms during daily activitiesand
respiratory exertion.

Inspiratory muscle training (IMT) is used by patients
with chronic obstructive pulmonary disease (COPD) to
improve strength and endurance of the inspiratory muscles in the hope that increased inspiratory muscle
strength will reduce the perceived effort of breathing
and ultimately reduce the intensity of dyspnea associated with a given level of ventilation. Thereis evidence
to suggest that IMT improves strength and endurance of
the inspiratory muscles if the intensity of training is ade-

KEY

WORDS

lung diseases, obstructive
breathing exercises
respiratory muscles
dyspnea
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, Divisionof 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 andPulmonary
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: mkcovey@uic.edu).

quate.1 But there is less evidence for its efficacy in producing a clinically meaningful reduction in dyspnea for
patients during activities of daily living.2,3Studies by Harver et al.4 and Lisboa et al.5 produce
the strongest evidence to suggest that IMT reduces dyspnea. In both studies patients trained at inspiratory
loads equal to 30% of maximal inspiratory pressure
(PImax) and reported improvements in inspiratory muscle strength and in dyspnea. Dyspnea was measured by
High-intensity Inspiratory Muscle Training / 231

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