DLCO: The diffusing capacity of the lung for carbon monoxide, also known as
TLCO : Transfer factor of the lung for carbon monoxide.
Used to determine transfer of gas from the distal airspaces-alveoli into the pulmonary capillaries.
- V(.) = uptake of CO in ml of CO at STPD conditions/min
- PACO2 is the average partial pressure of CO in alveoli
- PC(-)CO is the average partial pressure of CO in the pulmonary capillary plasma.
(Hb) has a very high affinity for CO (200 times > then 02).
Partial Pressure of CO in plasma (PC(-)) =0 when COHb is low
As a result, DLCO=V(.)CO/PACO
Increases in DLCO occur in:
- Pulmonary hemorrhage
- Diseases with increased blood flow
Decreases in DLCO occur in:
- Cardiovascular diseases
- Parenchymal lung disease (Fibrosis)