Comparison of incremental and constant load tests of inspiratory muscle endurance in COPD

• Published in: The European respiratory journal Vol. 30; no. 3; pp. 479 - 486
• Main Authors: Hill, K, Jenkins, S. C, Philippe, D. L, Shepherd, K. L, Hillman, D. R, Eastwood, P. R
• Format: Journal Article
• Language: English
• Published: Leeds Eur Respiratory Soc 01.09.2007; Maney
• Subjects: Aged; Airway Resistance - physiology; Biological and medical sciences; Chronic obstructive pulmonary disease, asthma; Double-Blind Method; Female; Forced Expiratory Volume - physiology; Humans; Inhalation - physiology; Male; Medical sciences; Middle Aged; Muscle Strength - physiology; Physical Endurance - physiology; Pneumology; Positive-Pressure Respiration, Intrinsic - physiopathology; Positive-Pressure Respiration, Intrinsic - rehabilitation; Prospective Studies; Pulmonary Disease, Chronic Obstructive - physiopathology; Pulmonary Disease, Chronic Obstructive - rehabilitation; Respiratory Muscles - physiology; Tidal Volume - physiology; Transducers, Pressure; Work of Breathing - physiology; Lung disease; Load; Chronic; Respiratory muscle; Respiratory disease; Assessment; Bronchus disease; Endurance; Obstructive pulmonary disease; respiratory muscles; Comparative study; Pneumology
• ISSN: 0903-1936; 1399-3003
• DOI: 10.1183/09031936.00095406

The aim of the present study was to determine the relative value of incremental and constant load tests in detecting changes in inspiratory muscle endurance following high-intensity inspiratory muscle training (H-IMT) in chronic obstructive pulmonary disease. In total, 16 subjects (11 males; forced expiratory volume in one second (FEV 1 ) 37.4±12.5%) underwent H-IMT. In addition, 17 subjects (11 males; FEV 1 36.5±11.5%) underwent sham inspiratory muscle training (S-IMT). Training took place three times a week for 8 weeks. Baseline and post-training measurements were obtained of maximum threshold pressure sustained during an incremental load test ( P th,max ) and time breathing against a constant load ( t lim ). Breathing pattern was unconstrained. H-IMT increased P th,max and t lim relative to baseline and to any change seen following S-IMT. The effect size for P th,max was greater than for t lim . Post-training tests were accompanied by changes in breathing pattern, including decreased duty cycle, which may have served to decrease inspiratory work and thereby contribute to the increase in P th,max and t lim in both groups. When assessing inspiratory muscle function in chronic obstructive pulmonary disease via tests in which the pattern of breathing is unconstrained, the current authors recommend incremental load tests be used in preference to constant load tests. However, to attribute changes in these tests to improvements in inspiratory muscle endurance, breathing pattern should be controlled.