Respiratory muscle strength, functional exercise capacity, and muscle oxygenation differences between COPD, PRISM,...

Preserved ratio-impaired spirometry (PRISm) is seen as an early stage of chronic obstructive pulmonary disease (COPD) and is associated with worsening respiratory function. However, the extent of pulmonary and extrapulmonary involvement in patients with PRISm remains unclear. This study aims to compare respiratory muscle strength and endurance, functional exercise capacity, peripheral muscle strength, muscle oxygenation, pulmonary function, dyspnea, and symptoms between COPD, PRISm, and healthy controls.

30 patients with COPD, 28 patients with PRISm, and 30 controls were compared. Respiratory (MIP, MEP) and peripheral muscle strength, inspiratory muscle endurance (IME), exercise capacity (6-min walk test (6MWT) and 6-min pegboard and ring test (6PBRT)), muscle oxygenation, pulmonary function, dyspnea (Modified Medical Research Council (MMRC) dyspnea scale), and symptoms (COPD Assessment Test (CAT)) were evaluated.

The COPD and PRISm groups had significantly lower MIP, MEP, IME, 6MWT distance, 6PBRT score, muscle oxygenation (especially at rest and recovery), pulmonary function, quadriceps femoris, and shoulder abductor muscle strength, and higher MMRC and CAT scores than the control group (p < 0.05). Except for forced vital capacity, pulmonary function parameters (p < 0.05), and IME (p = 0.022) were lower in the COPD group than in the PRISm group.

In patients with COPD and PRISm, respiratory muscle strength and endurance, peripheral muscle strength, functional exercise capacity, muscle oxygenation, and lung function are impaired; dyspnea increases. Consequently, PRISm patients experience pulmonary and extrapulmonary symptoms and functional impairment. Therefore, PRISm should be assessed from an early stage, pulmonary rehabilitation programs initiated as early as possible, and their outcomes investigated.