Incremental threshold loading in patients with chronic obstructive pulmonary disease.

The purpose of this research was to study the reproducibility of incremental threshold loading, a test of inspiratory muscle endurance, in patients with mild to severe chronic obstructive pulmonary disease. Twenty-seven patients completed four weekly visits. A significant difference was noted between the first visit and subsequent visits for the maximum absolute load that patients could tolerate, but no difference was noted in the load relative to inspiratory strength. Breathing pattern did not change significantly among visits to account for the differences in absolute load. Patients had a tendency to use rapid shallow breathing at the end of the test, suggesting that they approached the limits of their endurance and thus nearly fatigued their inspiratory muscles.