Diffusing capacity for carbon monoxide

D_LCO or T_LCO (

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 D_LCO is affected by atmospheric pressure and/or altitude and correction factors can be calculated using the method recommended by the American Thoracic Society.^[4] Expected D_LCO is also affected by the amount of hemoglobin, carboxyhemoglobin, age and sex. The correction for hemoglobin is based on the method of Cotes^[5][6] as recommended by the American Thoracic Society.

D_LCO vs T_LCO

Generally D_LCO is measured in "ml/min/

Factors affecting D_LCO

Decrease

D_LCO is decreased in any condition which affects the effective alveolar surface area:

1. Hindrance in the
   alveolitis, vasculitis
2. Decrease of total lung area, e.g. Restrictive lung disease or lung resection (partial or total).
3. Chronic obstructive pulmonary disease (Emphysema) due to decreased surface area in the alveoli, as well as damage to the capillary bed^[7]
4. Pulmonary embolism
5. Cardiac insufficiency^[8]
6. Pulmonary hypertension
7. Bleomycin (upon administration of more than 200 units)
8. Anemia-due to decrease in blood volume
9. Amiodarone high cumulative dose; more than 400 milligrams per day
10. After
    radiotherapy

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.^{[citation needed]}

Increase

Factors that can increase the D_LCO include

• Diffusing capacity

References