title: On the role of abnormal DL(CO) in ex-smokers without airflow limitation: symptoms, exercise capacity and hyperpolarised helium-3 MRI.
abstract: BACKGROUND
  The functional effects of abnormal diffusing capacity for carbon monoxide (DLCO) in ex-smokers without chronic obstructive pulmonary disease (COPD) are not well understood.
  
  
  OBJECTIVE
  We aimed to evaluate and compare well established clinical, physiological and emerging imaging measurements in ex-smokers with normal spirometry and abnormal DLCO with a group of ex-smokers with normal spirometry and DLCO and ex-smokers with Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage I COPD.
  
  
  METHODS
  We enrolled 38 ex-smokers and 15 subjects with stage I COPD who underwent spirometry, plethysmography, St George's Respiratory Questionnaire (SGRQ), 6 min Walk Test (6MWT), x-ray CT and hyperpolarised helium-3 ((3)He) MRI. The 6MWT distance (6MWD), SGRQ scores, (3)He MRI apparent diffusion coefficients (ADC) and CT attenuation values below -950 HU (RA950) were evaluated.
  
  
  RESULTS
  Of 38 ex-smokers without COPD, 19 subjects had abnormal DLCO with significantly worse ADC (p=0.01), 6MWD (p=0.008) and SGRQ (p=0.01) but not RA950 (p=0.53) compared with 19 ex-smokers with normal DLCO. Stage I COPD subjects showed significantly worse ADC (p=0.02), RA950 (p=0.0008) and 6MWD (p=0.005), but not SGRQ (p=0.59) compared with subjects with abnormal DLCO. There was a significant correlation for (3)He ADC with SGRQ (r=0.34, p=0.02) and 6MWD (r=-0.51, p=0.0002).
  
  
  CONCLUSIONS
  In ex-smokers with normal spirometry and CT but abnormal DLCO, there were significantly worse symptoms, 6MWD and (3)He ADC compared with ex-smokers with normal DLCO, providing evidence of the impact of mild or early stage emphysema and a better understanding of abnormal DLCO and hyperpolarised (3)He MRI in ex-smokers without COPD.
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada.
authors.forename: Miranda
authors.initials: M
authors.lastname: Kirby
authors.forename: Amir
authors.initials: A
authors.lastname: Owrangi
authors.forename: Sarah
authors.initials: S
authors.lastname: Svenningsen
authors.forename: Andrew
authors.initials: A
authors.lastname: Wheatley
authors.forename: Harvey O
authors.initials: HO
authors.lastname: Coxson
authors.forename: Nigel A M
authors.initials: NA
authors.lastname: Paterson
authors.forename: David G
authors.initials: DG
authors.lastname: McCormack
authors.forename: Grace
authors.initials: G
authors.lastname: Parraga
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000963:Antimetabolites / Q000493:pharmacokinetics; D002248:Carbon Monoxide / Q000493:pharmacokinetics*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume; D006371:Helium / Q000737:chemistry; D006801:Humans; D008297:Male; D008875:Middle Aged; D010991:Plethysmography; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000378:metabolism / Q000503:physiopathology; D012129:Respiratory Function Tests; D012907:Smoking; D011795:Surveys and Questionnaires; D014057:Tomography, X-Ray Computed; D014797:Vital Capacity
chemical_list: D000963:Antimetabolites; D006371:Helium; D002248:Carbon Monoxide
keywords: Emphysema; Imaging/CT MRI etc