Single breath diffusing capacity for carbon monoxide in stable asthma

Chest. 1994 May;105(5):1426-9. doi: 10.1378/chest.105.5.1426.


Background: Single breath diffusing capacity for carbon monoxide (Dco) is commonly used as a simple method of assessing overall pulmonary gas exchange properties. Studies of Dco in bronchial asthma have yielded conflicting results.

Objective: To study Dco and to determine the factors influencing Dco in patients with asthma.

Methods: Dco was prospectively measured in 80 consecutive never-smoker patients with uncomplicated stable asthma. The topographic distribution of lung perfusion was determined in 10 asthmatics and 10 controls, with a 133Xe radionuclide scan.

Results: The mean (SD) value of Dco was increased to 117 (17) percent of predicted values; individual values were either within or above normal limits; diffusion was also elevated at 116 (19) percent after correction for alveolar volume (transfer coefficient, D/VA). The Dco was not correlated with atopic status, duration of asthma, or results of spirometric tests; there was a weak negative correlation between D/VA and FEV1 or residual volume. There was a better perfusion of the upper zones of the lungs in asthmatics as compared with controls. Among the asthmatics, there was a strong positive correlation between Dco and the apex to base perfusion ratio (r = 0.975).

Conclusions: Dco is normal or high among never smoker patients with uncomplicated asthma; elevated Dco may be attributed to a better perfusion of the apices of teh lungs; the latter could result from two mutually nonexclusive mechanisms: an increase in pulmonary arterial pressure and/or a more negative pleural pressure generated during inspiration as a consequence of bronchial narrowing. The unexpected finding of high Dco should raise the possibility of bronchial asthma in patients with otherwise undiagnosed conditions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Asthma / diagnostic imaging
  • Asthma / physiopathology*
  • Carbon Monoxide / metabolism*
  • Female
  • Forced Expiratory Volume
  • Humans
  • Lung / diagnostic imaging
  • Male
  • Middle Aged
  • Prospective Studies
  • Pulmonary Diffusing Capacity*
  • Radionuclide Imaging
  • Residual Volume


  • Carbon Monoxide