Airway resistance and reactance are affected in systemic sclerosis

BACKGROUND Interstitial lung disease often occurs as an early complication of systemic sclerosis (SSc). The aim was to investigate whether impulse oscillometry (IOS) could be used to evaluate lung impairment in SSc. METHODS Seventy-eight SSc patients, of which 65 had limited cutaneous SSc (lcSSc) and 13 had diffuse cutaneous SSc (dcSSc), were subjected to high-resolution computed tomography (HRCT) and pulmonary function tests (spirometry, IOS, and single breath CO diffusion capacity test). Twenty-six healthy individuals served as controls. RESULTS Patients with lcSSc had higher levels of peripheral airway resistance, that is, R5-R20 (difference between resistance at 5 Hz and resistance at 20 Hz) showed a median (and interquartile range) of 0.05 (0.02-0.09) in lcSSc, 0.01 (0.00-0.04) in dcSSc and 0.04 (0.01-0.06) in healthy controls. They also had higher levels of reactance: reactance area was 0.26 (0.15-0.56) in lcSSc, 0.20 (0.11-0.29) in dcSSc and 0.18 (0.08-0.30) in healthy controls, and resonant frequency was 10.9 (8.8-14.8) in lcSSc, 9.0 (8.3-11.6) in dcSSc and 9.1 (8.0-13.1) in healthy controls. Airway reactance correlated to fibrotic findings on HRCT, such as ground glass opacities and reticulations. DISCUSSION This implies that IOS parameters to some extent are related to fibrosis in patients with SSc.