title: Exhaled ethane: an in vivo biomarker of lipid peroxidation in interstitial lung diseases.
abstract: BACKGROUND
  Oxidative stress plays a role in the pathogenesis and progression of interstitial lung disease (ILD). Exhaled ethane is a product of lipid peroxidation that has been proposed as a biomarker of oxidative stress in vivo.
  
  
  OBJECTIVE
  To determine whether the exhaled ethane level is elevated in patients with ILD and to compare it with other clinical parameters.
  
  
  METHODS
  Breath samples were collected from 34 patients with ILD, including 13 with idiopathic pulmonary fibrosis (IPF), 9 patients with cryptogenic organizing pneumonia, 6 patients with collagen vascular disease-associated interstitial pneumonia, and 6 patients with pulmonary sarcoidosis. Gas samples were obtained at hospital admission and after 3 weeks. After each expired sample was concentrated using a trap-and-purge procedure, the ethane level was analyzed by gas chromatography.
  
  
  RESULTS
  Exhaled ethane levels were elevated in ILD patients (n = 34, mean +/- SD, 8.5 +/- 8.0 pmol/dL) compared with healthy volunteers (n = 16, 2.9 +/- 1.0 pmol/dL; p < 0.001). Serial measurements revealed that increase and decrease of ethane levels were largely consistent with the clinical course. Four patients with IPF who had persistently high ethane levels died or deteriorated, whereas those with ethane levels < 5.0 pmol/dL remained stable or improved. Exhaled ethane concentrations were positively correlated with levels of lactate dehydrogenase (Spearman rank correlation coefficient [rs], 0.28, p = 0.026) and C-reactive protein (rs, 0.38, p = 0.025) and were inversely correlated with Pa(O2) (rs, - 0.40, p = 0.0026). Patients showing increased uptake on (67)Ga scintigraphy demonstrated higher ethane levels (n = 19, 7.5 +/- 5.7 pmol/dL) compared with those who did not show increased uptake on scintigraphy (n = 10, 3.0 +/- 2.4 pmol/dL; p < 0.01).
  
  
  CONCLUSIONS
  Exhaled ethane is elevated in patients with ILD and is correlated with the clinical outcome, suggesting that it provides useful information about ongoing oxidative stress, and thereby disease activity and severity in ILD.
authors.affiliation: Third Department of Internal Medicine, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan. kanoh@ndmc.ac.jp
authors.forename: Soichiro
authors.initials: S
authors.lastname: Kanoh
authors.forename: Hideo
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Kazuo
authors.initials: K
authors.lastname: Motoyoshi
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000032:analysis; D001944:Breath Tests; D003937:Diagnosis, Differential; D004980:Ethane / Q000032:analysis*; D005260:Female; D006801:Humans; D015227:Lipid Peroxidation; D017563:Lung Diseases, Interstitial / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000175:diagnosis; D011658:Pulmonary Fibrosis / Q000175:diagnosis; D012016:Reference Values
chemical_list: D015415:Biomarkers; D004980:Ethane