DLCO UNC

Diffusion capacity uncorrected

Patient is asked to take a deep breath of air containing known concentration of carbonmonoxide and to hold it for 10 seconds. The terminal (alveolar air) portion of expiration is collected to measure CO concentration. Diffusion capcity is then calculated using a complex formula.
The normal range is 75-125% predicted.

 

 

 

 

 

 

 

 

 

 

DLCO CORR

Diffusion capacity corrected

A correction for predicted value is made using patients Hemoglobin.

The normal range is 75-125% predicted.

 

 

 

 

 

 

 

VA @BTPS and DL/VA

Single breath TLC (VA @BTPS) is measured simultaneously by adding known concentration of Helium to measure alveolar volume exposed to Carbonmonoxide. This alveolar volume is used in expressing diffusion capacity for unit lung volume ie DL/VA.

The normal range is 75-125% predicted.

 

 

 

 

 

 

 

 

 

 

 

Factors affecting DLCO

Primary purpose of measuring diffusion capacity is to assess
the barrier for gas transfer at alveolar capillary membrane.
Before we can ascribe a given dicrease in diffusion to AC block
we have to make corrections for variables that can affect
diffusion.

  • Hemoglobin: DLCO CORR
  • Lung volume: DL/VA
  • V/Q mismatch:
  • Pulmonary capillary bed:
  • Alveolar capillary membrane thickness:

 

 

 

 

 

 

 

 

 

 

 

 

 

Note:
  • Duration of breath hold
  • Volume of inspiration
  • Start of expiration