Lung diffusion testing


Lung Diffusion Testing

Lung diffusion testing, also called lung diffusion capacity, measures the ability of oxygen and carbon dioxide gases to move between the small air sacs in your lungs and your bloodstream. It helps assess how well oxygen and carbon dioxide are exchanged by your lungs.


  • To prepare for a lung diffusion test, you should wear loose, comfortable clothing so the technician can easily attach the sensors.
  • Before the test, your doctor may ask you to stop taking medications or supplements that affect breathing, such as bronchodilators, for 24 hours.
  • Tell your doctor if you’re pregnant, have recently had surgery or experience anxiety.


  • A lung diffusion test is performed at a hospital or clinic by a trained technician.
  • You’ll be asked to breathe in and out of a tube connected to two large sensors.
  • The tube measures pulmonary results, such as your breathing rate, oxygen and carbon dioxide levels.
  • Ogston equations.
  • The results of the tests are collected and the data entered into a computer.
  • The computer then uses the data to calculate lung diffusion capacity.


  • There are two primary types of lung diffusion tests.
  • The first is an open-circuit test, which uses a tube to measure the volume and flow of inhaled and exhaled air.
  • The second test is a closed-circuit test, which uses a constant low-pressure gas mixture to measure lung diffusion capacity.


  • Lung diffusion testing is generally considered safe and is generally not painful.
  • Very rarely, the tests may cause minor discomfort or dizziness.
  • In some cases, the testing may cause carbon dioxide levels in the blood to drop.


Lung diffusion tests are used to diagnose various lung diseases, such as Chronic Obstructive Pulmonary Disease (COPD), asthma, interstitial lung disease, and lung cancer. The tests are also used to measure the effectiveness of treatments for certain lung diseases.


Your doctor may suggest a lung diffusion test if you’re experiencing shortness of breath, wheezing, a persistent cough, or other symptoms associated with lung diseases. Your doctor may also suggest a test if you’re at risk of lung diseases, such as if you smoke or have been exposed to asbestos.