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Evaluation of diffusing capacity in patients with a restrictive lung disease
H Stam1, T A Splinter, A Versprille
1Pathophysiology Laboratory of the Department of Pulmonary Diseases, Erasmus University, Rotterdam, the Netherlands.
Chest
|March 14, 2000
Summary
Comparing diffusing capacity of the lung for carbon monoxide (DLCO) normalized per alveolar volume (VA) in patients with restrictive lung disease requires careful consideration of lung volumes. This study suggests comparing DLCO/VA at actual total lung capacity (TLC) to a reference value at the same lung volume to accurately assess diffusion disorders.
Area of Science:
- Pulmonary Medicine
- Respiratory Physiology
- Clinical Diagnostics
Background:
- The single-breath diffusing capacity of the lung for carbon monoxide (DLCO) and its normalized value (DLCO/VA) exhibit specific relationships with lung volume in healthy individuals.
- It was hypothesized that using predicted total lung capacity (TLC) for DLCO/VA assessment in restrictive lung disease could underestimate diffusion disorders.
Purpose of the Study:
- To investigate the relationship between DLCO/VA and alveolar volume (VA) in patients with restrictive lung disease and diffusion impairment.
- To test the hypothesis that DLCO/VA normalized to predicted TLC may underestimate diffusion abnormalities.
Main Methods:
- Observational survey conducted in a pulmonary function department.
- Studied thirteen patients treated with bleomycin who developed restrictive lung disease and diffusion disorders.
- Performed single-breath DLCO tests at various VA levels before, during, and after bleomycin treatment.
Main Results:
- The DLCO vs. VA relationship generally remained parabolic but shifted downward during bleomycin therapy, indicating reduced gas transfer.
- The DLCO/VA vs. VA relationship also shifted downward, with unchanged negative slope, confirming impaired diffusion.
- Six patients developed concurrent volume restriction.
Conclusions:
- The study's findings support the hypothesis that DLCO/VA assessment in restrictive lung disease needs adjustment for actual lung volumes.
- For accurate evaluation of diffusion disorders in patients with lung restriction, DLCO/VA at their actual TLC should be compared to a reference DLCO/VA at an equivalent lung volume.