Background and aim of the work: We evaluated the clinical consequences of inspiratory muscle impairment on exercise tolerance and quality of life in 34 sarcoid patients compared with 19 controls.
Methods: We measured pulmonary function tests, inspiratory muscle strength by maximal inspiratory pressure (PImax) and inspiratory muscle endurance (IME) by an incremental threshold loading test. IME was defined by the maximal sustainable pressure for 2 minutes (Plim2) and Plim2/PImax. Cycloergometer incremental exercise testing was performed in all patients. Health-related quality of life (HRQOL) was assessed by the SF-36 questionnaire in comparison with scores of 116 French controls. Dyspnea was assessed by the Modified Dyspnea Index (MDI).
Results: All SF-36 subscales were lower in sarcoid patients (p < 0.05). PImax% pred was similar in both groups whereas IME was markedly lower in sarcoid patients (p < 0.0001). Plim2 correlated with MDI (r = 0.44; p = 0.01) and SF-36 scales Physical Functioning (PF) (r = 0.42; p = 0.034) and Physical Role (PR) (r = 0.63; p = 0.0016). Plim2/PImax correlated with SF-36 subscales: PR (r = 0.62), vitality (VT) (r = 0.56) and social functioning (SF) (r = 0.39). Plim2 (r = 0.639; p = 0.0002) and Plim2/PImax (r = 0.36; p = 0.036) correlated with peak exercise tidal volume (V(T)max) but not with VO2max.
Conclusions: Inspiratory muscle impairment was related to physical HRQOL scores but not to exercise tolerance, although it could impair exercising V(T) through an incipient inspiratory muscle fatigue.