Diffusion Capacity

Diffusing capacity is a measure of how well oxygen and carbon dioxide are transferred (diffused) between the lungs and the blood. It is a useful test in the diagnosis and to monitor treatment of lung diseases.

How is diffusion capacity measured?

Diffusion capacity also called as DLco is measured in the by having the child hold his breath at full lung capacity (TLC) for 10 s after breathing a dilute mixture of carbon monoxide (CO). During the breath hold, the Carbon Monoxide diffuses into the blood. The amount of carbon monoxide (CO) exhaled after the 10-second breath hold is measured and subtracted from the initial amount, giving the quantity of carbon monoxide (CO) diffused in a 10-second period.

What are the conditions when DLco is reduced?

A low DLco indicates:

  • Pulmonary interstitial thickening in children with diffuse parenchymal lung disease [DPLD]
  • Pulmonary vascular disease
  • Idiopathic pulmonary arterial hypertension