Background: Sarcoidosis is a systemic granulomatous
disorder that is estimated to involve the skeletal muscles in up to
50% of patients. There is little information on the relationship among
respiratory muscle strength, lung volumes, and the degree of dyspnea in
patients with sarcoidosis.
Design and patients: Lung
function and maximal respiratory muscle force generation were measured
in 36 patients with sarcoidosis (24 patients with pulmonary parenchymal
infiltration) and 25 control subjects free of cardiorespiratory
disease. Dyspnea in the sarcoidosis patients was quantitated by a score
based on an activity tolerance assessment scale (ranging from rest to
climbing hills or stairs).
Setting: Outpatient clinics
of two teaching hospitals.
Results: Mean FVC, maximal
voluntary ventilation, total lung capacity (TLC), functional residual
capacity, residual volume (RV), and diffusing capacity of the lung for
carbon monoxide (Dlco) were all at least 16% less than
corresponding control values (in all cases, p < 0.001), while
maximal inspiratory mouth pressure (Pimax) and maximal
expiratory mouth pressure (Pemax) were 37% and 39% less,
respectively, than control values (both at p < 0.0001).
Pimax and Pemax declined with increasing
dyspnea in a more graded, steady manner than did spirometric and
Dlco values. For all measurements, however, the lowest mean
values were found in patients with the most severe level of dyspnea.
Strong inverse relationships were observed between Pemax
and Pimax with dyspnea level (p < 0.0001 and
p < 0.01, respectively). Both Pimax and
Pemax correlated best with absolute values of FVC, while
only Pemax correlated with RV (absolute and percent
predicted) and percent predicted values of TLC.
Conclusions: Maximal respiratory pressures correlate more
closely with dyspnea level than lung volumes and Dlco.
Since dyspnea is the most common presentation in early to moderately
advanced sarcoidosis, respiratory pressures may be a more reliable
index of functional work capacity and reflection of activities of daily
living than standard tests of lung function.