Reduction of exercise capacity in sarcoidosis in relation to disease severity

Abstract

Introduction: Pulmonary function tests (PFTs) do not always predict functional limitations during exercise in sarcoidosis. Cardiopulmonary exercise testing (CPET) may facilitate the recognition of exercise intolerance in these patients.

Aim: As relevant data in sarcoid patients are limited, the aim of the study reported here was to assess exercise capacity impairment during a maximal CPET and to evaluate potential correlations with PFT measurements and radiological stages of the disease.

Method: A total of 83 sarcoid patients consecutively referred for evaluation of exertional dyspnea over a 3-year period were studied retrospectively with PFTs, including spirometry, diffusing capacity of the lung for carbon monoxide (DLCO) and lung volumes, and CPET using standard protocol. Patients were grouped according to their radiological stages: Stage I (n=43), Stages II-III (n=31), and Stage IV (n=9).

Results: Forced expiratory volume in 1 second, forced vital capacity, and total lung capacity were mildly impaired only in Stage IV (means ± standard deviation: 72.44±28.00, 71.33±26.70, and 59.78±21.72, respectively), while DLCO was mildly and moderately reduced in Stages II-III and IV (72.68±14.13 and 51.22±18.50, respectively) and differed significantly between all stages (I vs II-III: P=0.003, I vs IV: P=0.003, and II-III vs IV: P=0.009). Exercise capacity (as expressed by peak oxygen consumption <84% predicted) was decreased in 53% of patients (Stage I: 48%, Stages II-III: 52%, Stage IV: 78%); however, significant differences were noticed only between Stages I and IV (P=0.0025). Of note, significant correlations were found between peak oxygen consumption and DLCO (P=0.0083), minute ventilation (P<0.0001), oxygen pulse (P<0.0001), lactate threshold (P<0.0001), and peak ventilatory threshold (P<0.0001).

Conclusion: CPET could be considered a useful tool in exercise intolerance evaluation in sarcoid patients with mild PFT abnormalities. Exercise limitation in sarcoidosis may be attributed to both ventilatory and cardiocirculatory impairment.

Keywords: cardiopulmonary exercise testing; exercise; pulmonary function tests.

Figure 1

VO₂ peak correlations with clinical, functional, and cardiopulmonary test parameters in 83 patients with sarcoidosis. Note: P<0.001 for all comparisons. Abbreviations: FVC%, percent forced vital capacity; %pred, percent predicted; AT, anaerobic threshold; DLCO, diffusing capacity of the lung for carbon monoxide; V_E, minute ventilation; VO₂ peak, peak oxygen consumption; V_T, tidal volume.

Figure 2

Biplot of correlation coefficients (loading factors) of ergo/spirometric variables with PCA axes 1 and 2. The longer the arrow the greater effect is produced by the variable. Variables forming oblique angles correlate positively with each other and negatively at arrows with obtuse angles. The lower oblique or wider obtuse aperture the higher the correlation coefficient. Abbreviations: AT, anaerobic threshold; DLCO, diffusing capacity of the lung for carbon monoxide; FEF_25–75, forced expiratory flow 25%–75%; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; FVC%, percent forced vital capacity; HR, heart rate; PCA, principal component analysis; RV%, percent residual volume; TLC, total lung capacity; VCO₂, carbon dioxide production; V_E, minute ventilation; VO₂, oxygen consumption; V_T, tidal volume; vom%, maximal aerobic capacity.

Figure 3

PCA scores and patients position as arranged by the two major axes according to radiological Stages I–III and the combined presence/absence of ecto-pneumonic location and restriction rules. Abbreviation: PCA, principal component analysis.

Figure 4

Mean changes of the significant ergo-/spirometric variables with the radiological conditions 1–3. Abbreviations: DLCO%, percent diffusing capacity of the lung for carbon monoxide; FEV₁%, percent forced expiratory volume in 1 second; FEF_25–75, forced expiratory flow 25%–75%; FVC%, percent forced vital capacity; TLC, total lung capacity; VCO₂, carbon dioxide production; VO₂, oxygen consumption; VO₂ max, maximum oxygen consumption; vom%, maximal aerobic capacity; V_D, deadspace; V_E, minute ventilation; V_T, tidal volume; vom%, maximal aerobic capacity; HR, heart rate.

Figure 5

Mean changes of VO₂ peak along with the ordinal categories of diffusing capacity of the lung for carbon monoxide (DLCO). Notes: Vertical lines indicate the 95% confidence intervals of means calculated from the error mean square of analysis of variance. Means whose intervals do not overlap differ significantly.