title: Airway resistance and reactance are affected in systemic sclerosis.
abstract: 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.
  
  
  CONCLUSIONS
  This implies that IOS parameters to some extent are related to fibrosis in patients with SSc.
authors.affiliation: Respiratory Medicine and Allergology, Department of Clinical Sciences Lund, Skåne University Hospital, Lund University, Lund, Sweden.
authors.forename: David
authors.initials: D
authors.lastname: Aronsson
authors.affiliation: Rheumatology, Department of Clinical Sciences Lund, Skåne University Hospital, Lund University, Lund, Sweden.
authors.forename: Roger
authors.initials: R
authors.lastname: Hesselstrand
authors.affiliation: Diagnostic Radiology, Department of Clinical Sciences Lund, Skåne University, Hospital, Lund University, Lund, Sweden.
authors.forename: Gracijela
authors.initials: G
authors.lastname: Bozovic
authors.affiliation: Rheumatology, Department of Clinical Sciences Lund, Skåne University Hospital, Lund University, Lund, Sweden.
authors.forename: Dirk M
authors.initials: DM
authors.lastname: Wuttge
authors.affiliation: Respiratory Medicine and Allergology, Department of Clinical Sciences Lund, Skåne University Hospital, Lund University, Lund, Sweden; Ellen.Tufvesson@med.lu.se.
authors.forename: Ellen
authors.initials: E
authors.lastname: Tufvesson
keywords: fibrosis; impulse oscillometry; reactance; resistance; systemic sclerosis