title: Determinants of impairment in lung diffusing capacity in patients with systemic sclerosis.
abstract: OBJECTIVE
  Lung diffusing capacity for carbon monoxide (DLCO) is impaired in interstitial lung disease (ILD) and pulmonary arterial hypertension (PAH) associated to systemic sclerosis (SSc), but the mechanism of DLCO reduction remains controversial. We hypothesised that the determinants of DLCO impairment differ in interstitial or vascular involvement of the lung of SSc patients.
  
  
  METHODS
  DLCO was partitioned into alveolar-capillary membrane conductance (Dm) and pulmonary capillary blood volume (Vc) using combined single-breath DLNO and DLCO measurements. Seventeen SSc patients without pulmonary involvement (SSc), 20 SSc patients with ILD (SSc-ILD), with and without PAH, and 21 healthy controls were included.
  
  
  RESULTS
  DLNO and Dm were reduced in SSc patients as compared with controls, whereas Vc was not significantly different. SSc-ILD patients showed a highly significant decrease in Dm and Vc as compared with SSc patients and controls. Vc tended to be more reduced than Dm in SSc-ILD patients with PAH. Dm and Vc were negatively correlated with PAPs and HCRT scores, but the relationship with the HRCT score was stronger.
  
  
  CONCLUSIONS
  DLNO is more sensitive than DLCO in detecting functional impairment in SSc without radiologic or haemodynamic alterations. A disproportional reduction of Dm relative to Vc suggests a thickening of the blood-gas diffusion barrier in these patients. In SSc patients with detectable ILD, the gas exchange impairment is due to both components of lung diffusing capacity, and partitioning of DLCO in Dm and Vc is of little use in distinguishing the patients with only ILD from those with ILD complicated by PAH.
authors.affiliation: Department of Cardiologic, Thoracic and Vascular Sciences, University of Padova, Padova, Italy.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Guarnieri
authors.affiliation: Rheumatology Unit, Department of Medicine, University of Padova, Padova, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Zanatta
authors.affiliation: Department of Cardiologic, Thoracic and Vascular Sciences, University of Padova, Padova, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Mason
authors.affiliation: Department of Cardiologic, Thoracic and Vascular Sciences, University of Padova, Padova, Italy.
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Scarpa
authors.affiliation: Rheumatology Unit, Department of Medicine, University of Padova, Padova, Italy.
authors.forename: Erika
authors.initials: E
authors.lastname: Pigatto
authors.affiliation: Department of Cardiologic, Thoracic and Vascular Sciences, University of Padova, Padova, Italy. piero.maestrelli@unipd.it.
authors.forename: Piero
authors.initials: P
authors.lastname: Maestrelli
authors.affiliation: Rheumatology Unit, Department of Medicine, University of Padova, Padova, Italy.
authors.forename: Franco
authors.initials: F
authors.lastname: Cozzi
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D018916:Blood-Aqueous Barrier / Q000378:metabolism / Q000473:pathology; D001944:Breath Tests; D002199:Capillary Permeability; D002248:Carbon Monoxide / Q000097:blood; D016022:Case-Control Studies; D005260:Female; D006439:Hemodynamics; D006801:Humans; D006976:Hypertension, Pulmonary / Q000097:blood / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D008168:Lung / Q000503:physiopathology*; D017563:Lung Diseases, Interstitial / Q000097:blood / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000097:blood; D011237:Predictive Value of Tests; D011653:Pulmonary Diffusing Capacity; D012595:Scleroderma, Systemic / Q000150:complications* / Q000175:diagnosis; D013147:Spirometry
chemical_list: D015415:Biomarkers; D009569:Nitric Oxide; D002248:Carbon Monoxide