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On the role of abnormal DLCO in ex-smokers without airflow limitation: symptoms, exercise capacity and hyperpolarised helium-3 MRI
  1. Miranda Kirby1,2,
  2. Amir Owrangi1,3,
  3. Sarah Svenningsen1,2,
  4. Andrew Wheatley1,
  5. Harvey O Coxson4,
  6. Nigel A M Paterson5,
  7. David G McCormack5,
  8. Grace Parraga1,2,3,6
  1. 1Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada
  2. 2Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada
  3. 3Graduate Program in Biomedical Engineering, University of Western Ontario, London, Ontario, Canada
  4. 4Department of Radiology and James Hogg Research Centre, University of British Columbia and Vancouver General Hospital, Vancouver, British Columbia, Canada
  5. 5Division of Respirology, Department of Medicine, University of Western Ontario, London, Ontario, Canada
  6. 6Department of Medical Imaging, University of Western Ontario, London, Ontario, Canada
  1. Correspondence to Dr G Parraga, Imaging Research Laboratories, Robarts Research Institute, 100 Perth Drive, London, Canada N6A 5K8; gparraga{at}


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 (3He) MRI. The 6MWT distance (6MWD), SGRQ scores, 3He 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 3He 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 3He 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 3He MRI in ex-smokers without COPD.

  • Emphysema
  • Imaging/CT MRI etc

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