[2] This test involves measuring the partial pressure difference between inspired and expired carbon monoxide.
It relies on the strong affinity and large absorption capacity of red blood cells for carbon monoxide and thus demonstrates gas uptake by the capillaries that are less dependent on cardiac output.
[3] The measurement of DLCO is affected by atmospheric pressure and/or altitude and correction factors can be calculated using the method recommended by the American Thoracic Society.
The correction for hemoglobin is based on the method of Cotes[5][6] as recommended by the American Thoracic Society.
DLCO is decreased in any condition which affects the effective alveolar surface area: However, many modern devices compensate for the hemoglobin value of the patient (taken by blood test), and excludes it as a factor in the DLCO interpretation.