Background: In healthy volunteers, the single-breath
diffusing capacity of the lung for carbon monoxide (Dlco)
decreases and Dlco normalized per liter alveolar volume
(Va; Dlco/Va) increases if
Va is decreased. We hypothesized that comparison of
Dlco/Va with its predicted value at predicted
total lung capacity (TLC) will result in an underestimation of the
diffusion disorder in patients with a restrictive lung disease, if a
similar relationship exists between Dlco/Va and
lung volume as found in healthy volunteers.
Objective: To test this hypothesis, we studied total gas
transfer Dlco and Dlco/Va as
functions of Va in patients who developed a restrictive
lung disease and a diffusion disorder in a short period of time.
Design: An observational survey.
Pulmonary function department.
patients without any initial pulmonary pathology who developed the
mentioned pulmonary pathology due to bleomycin treatment.
Interventions: Bleomycin treatment.
and results: We performed the single-breath test at various
Va levels before, during, and after bleomycin treatment. In
the majority of the patients, the Dlco vs Va
relationship remained parabolic, but shifted downwards during therapy.
Therefore, the linear Dlco/Va vs Va
relationship shifted downwards, while the negative slope was not
changed, indicating the development of a decreased gas transfer. Six
patients also developed a volume restriction.
Conclusions: The agreement of the data with the hypothesis
increased its probability. Consequently, to evaluate a diffusion
disorder, Dlco/Va at a lower actual TLC of
patients with a lung restriction should be compared to a reference
Dlco/Va at a lung volume equal to the actual