Retrospective Study of Pulmonary Function Tests in Patients Presenting With Isolated Reduction in Single-Breath Diffusion Capacity: Implications for the Diagnosis of Combined Obstructive and Restrictive Lung Disease

doi:10.4065/82.1.48

Mayo Clinic Proceedings

Volume 82, Issue 1, January 2007, Pages 48-54

https://doi.org/10.4065/82.1.48 Get rights and content

OBJECTIVE

To examine the frequency and spectrum of diseases associated with isolated reduction in the diffusing capacity of lung for carbon monoxide (Dlco).

PATIENTS AND METHODS

We retrospectively identified all potentially dyspneic patients who had pulmonary function tests (PFTs) performed at the Mayo Clinic in Jacksonville, Fla, between January 1, 1990, and June 30, 2000, that showed reduced Dlco (<70% of predicted), normal lung volumes (total lung capacity and residual volume >80% and <120% of predicted, respectively), and airflow variables (forced expiratory volume in 1 second and forced vital capacity values >80% of predicted and forced expiratory volume in 1 second/forced vital capacity ratio >70% of predicted). Only patients who had also undergone chest computed tomography (CT) and echocardiography within 1 month of PFTs were studied.

RESULTS

Of the 38,095 patients who underwent PFTs during the study period, 179 (0.47%; 95% confidence interval [CI], 0.40%-0.54%) had isolated Dlco abnormalities. The 27 patients (15.1%; 95% CI, 10.2%-21.2%) who had also undergone chest CT and echocardiography within 1 month of PFTs form the study cohort reported herein. Their mean Dlco was 50%±15% (95% CI, 45%-56%) with average normal pulse oxygen saturation at rest and mild hypoxemia with activity. Thirteen of the 27 patients (48%; 95% CI, 28.7%-68.1%) had underlying emphysema evident on CT. Eleven of these 13 patients had emphysema associated with a restrictive lung process. The 14 patients without emphysema had interstitial lung disease, pulmonary vascular disease, and other isolated findings. Six patients with combined emphysema and idiopathic pulmonary fibrosis accounted for the largest percentage (22%) of patients with isolated Dlco reduction. The mean ± SD smoking history of the 27 patients in the study cohort was 36±33 pack-years (range, 0-116 pack-years).

CONCLUSION

Dyspneic patients with respiratory symptoms and normal lung volumes and airflows associated with isolated reduction in Dlco should be evaluated for underlying diseases such as emphysema, with or without a concomitant restrictive process, and pulmonary vascular disease.

Section snippets

PATIENTS AND METHODS

With Mayo Foundation Institutional Review Board approval, we retrospectively reviewed the pulmonary function database at the Mayo Clinic in Jacksonville, Fla, to identify complete PFTs performed between January 1, 1990, and June 30, 2000, in patients complaining of dyspnea. Pulmonary function studies included measurements of airflow, plethysmographic lung volumes, and Dlco (measured by the single-breath diffusion capacity method), with the aim of identifying patients with reduced Dlco but

Patient Cohort

Of the 38,095 patients who had pulmonary function studies archived in our database during the period of this study, 179 had an isolated reduction in Dlco (0.47%; 95% confidence interval [CI], 0.40%-0.54%). Twenty-seven of these 179 patients (15.1%; 95% CI, 10.2%-21.2%) had also undergone standard chest CT and echocardiography within 1 month of their PFTs, 16 of whom had also undergone HRCT.

Clinical Diagnoses and Physiologic Assessments

Final diagnosis, demographic data, PFT results, Dlco measurements, oxygen saturation values, and

DISCUSSION

Measurements of Dlco assess the transfer of gases from the alveoli to red blood cells. The frequency and importance of reduced Dlco in patients with otherwise normal PFT results have not been systematically explored. This retrospective clinical study provides some insight into this situation.

We have determined that in patients with dyspnea, an isolated reduction in Dlco is extremely rare (<1%). However, when present, it is commonly associated with emphysema and a concurrent restrictive process.

CONCLUSION

Reduction in Dlco in the context of normal lung volumes and airflows is an uncommon finding among patients evaluated for dyspnea. Isolated reduction in Dlco can frequently be explained by the association of emphysema with a restrictive lung process such as ILD or pulmonary edema/CHF. Interstitial lung disease, pulmonary vascular conditions, or both explain most of the remaining cases. Isolated reduction in Dlco should prompt further clinical investigation and evaluation with HRCT and

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ORIGINAL ARTICLERetrospective Study of Pulmonary Function Tests in Patients Presenting With Isolated Reduction in Single-Breath Diffusion Capacity: Implications for the Diagnosis of Combined Obstructive and Restrictive Lung Disease

OBJECTIVE

PATIENTS AND METHODS

RESULTS

CONCLUSION

Section snippets

PATIENTS AND METHODS

Patient Cohort

Clinical Diagnoses and Physiologic Assessments

DISCUSSION

CONCLUSION

Clin Chest Med

Clin Chest Med

Respir Med

Respir Med

Chest

J Am Coll Cardiol

Clin Chest Med

Br J Dis Chest

Chest

Chest

J Am Coll Cardiol

Chest

Am J Pathol

Chest

Standards for the diagnosis and care of patients with chronic obstructive pulmonary disease

Am J Respir Crit Care Med

Pulmonary function testing in interstitial lung diseases

Respiration

Interpreting pulmonary function tests: recognize the pattern, and the diagnosis will follow

Cleve Clin J Med

Isolated reduction in single-breath diffusion capacity in young, healthy, asymptomatic women

Am J Med Sci

Isolated diffusing capacity reduction in systemic sclerosis

Arthritis Rheum

Cryptogenic fibrosing alveolitis with preserved lung volumes

Thorax

ORIGINAL ARTICLE
Retrospective Study of Pulmonary Function Tests in Patients Presenting With Isolated Reduction in Single-Breath Diffusion Capacity: Implications for the Diagnosis of Combined Obstructive and Restrictive Lung Disease