Ventilation distribution as a contributor to the functional exercise capacity in patients with systemic sclerosis-associated interstitial lung disease without pulmonary hypertension

Abstract

Phenotypic differences have been described between patients with systemic sclerosis (SSc)-associated interstitial lung disease (ILD) and SSc-associated pulmonary hypertension, including performance differences in the 6-min walk test (6MWT). Moreover, the correlations between the 6MWT and traditional pulmonary function tests (PFTs) are weak, indicating the need to search for new parameters that explain exercise performance. Thus, our objective was to evaluate the impact of ventilation distribution heterogeneity assessed by the nitrogen single-breath washout (N 2 SBW) test and peripheral muscle dysfunction on the exercise capacity in patients with SSc-ILD and limited involvement of the pulmonary parenchyma. In this cross-sectional study, 20 women with SSc-ILD and 20 matched controls underwent PFTs (including spirometry, diffusing capacity for carbon monoxide (DLco), and the N 2 SBW test) and performed the 6MWT and knee isometric dynamometry. The 6-min walking distance (6MWD, % predicted) was strongly correlated with the phase III slope of the single-breath nitrogen washout (phase III slope N2SBW ) (r=−0.753, P<0.0001) and reasonably correlated with the forced vital capacity (FVC) (r=0.466, P=0.008) and DLco (r=0.398, P=0.011). The peripheral oxygen saturation (SpO 2 ) during exercise was not significantly correlated with any of the pulmonary or muscle function parameters. The phase III slope N2SBW was the only predictive variable for the 6MWD, whereas quadriceps strength and FVC/DLco were predictive variables for SpO 2 . Ventilation distribution heterogeneity is one factor that contributes to a lower 6MWD in SSc-ILD patients. In addition, muscle dysfunction and abnormal lung diffusion at least partly explain the decreased SpO 2 of these patients.

High-intensity interval training can improve hand grip strength, inspiratory muscle, and quality of life in systemic sclerosis subjects

“…Moreover, training tests on ILD and pulmonary hypertension also showed an increase in exercise capacity, and decreased symptoms and quality of life after the addition of a respiratory muscle rehabilitation exercise program. In our study, significant results were obtained in the inspiratory strength of the muscles on examination with the SNIP method [ 12 , 13 , 19 ].…”

Pulmonary involvement in patients with juvenile systemic sclerosis

“…Interestingly, clinical or radiological evidence of severe or progressive pulmonary fibrosis on chest X-rays is a strong predictor of death at presentation and is associated with increased mortality 23,25 . Six-minute walk test is a noninvasive indicator of cardiopulmonary function that proved to be the most useful in PAH, with a poor correlation between distance traveled and measures of lung function 26,27 . The interpretation of 6MWT can be confusing in patients with SSc, as they have a cardiopulmonary or musculoskeletal disease and present combinations of cardiac involvement, even in the presence of normal echocardiogram, pulmonary disease, skin fibrosis, muscle damage, and joint disease 27 .…”

“…Six-minute walk test is a noninvasive indicator of cardiopulmonary function that proved to be the most useful in PAH, with a poor correlation between distance traveled and measures of lung function 26,27 . The interpretation of 6MWT can be confusing in patients with SSc, as they have a cardiopulmonary or musculoskeletal disease and present combinations of cardiac involvement, even in the presence of normal echocardiogram, pulmonary disease, skin fibrosis, muscle damage, and joint disease 27 . An abnormal 6MWT was identified in a few patients of the present study.…”

Predictors of functional capacity as measured by the Glittre activities of daily living test in women with rheumatoid arthritis

“…In addition, the N 2 SBW test was carried out in an HDpft 3000 testing system (nSpire Health, Inc.) following established standards ( 23 ). To evaluate ventilation distribution heterogeneity, we used the phase III slope of the N 2 SBW test (SIIIN 2 ) ( 23 - 26 ), and the results are reported as the percentage of predicted values ( 27 ).…”