What is lung diffusion capacity?

Lung diffusion capacity is a simple, painless test to determine how well oxygen moves or diffuses into your bloodstream from your lungs. Doctors use lung diffusion capacity to diagnose and monitor conditions that affect the lungs’ ability to transfer oxygen into the bloodstream. Conditions include emphysema, cystic fibrosis, and pulmonary embolism (blood clot in the lungs).

Lung diffusion capacity is only one method of diagnosing and monitoring respiratory diseases. Discuss all of your testing options with your doctor to understand which options are right for you.

Other procedures that may be performed

Lung diffusion capacity is a type of pulmonary or lung function test. Your doctor will may perform one or more other pulmonary function tests to diagnose and monitor your respiratory disease, disorder or condition. Other pulmonary function tests include:

  • Arterial blood gas test to measure oxygen and carbon dioxide levels and other factors in the blood 
  • Body plethysmography to determine how much air is present in your lungs when you take a deep breath and how much air is left in your lungs after you exhale as much as you can. Lung diffusion capacity may be done at the same time as a body plethysmography using the same equipment.
  • Bronchoprovocation tests to measure lung function after exposure to factors that commonly trigger asthma. This includes a methacholine challenge test to help diagnose asthma. 
  • Peak expiratory flow to measure the speed of exhaling and lung constriction. People with asthma use this test routinely to monitor their asthma control.
  • Pulse oximetry to measure oxygen levels in the blood
  • Spirometry to measure the rate and amount of air that you inhale and exhale

Why is lung diffusion capacity used? 

Your doctor may recommend lung diffusion capacity testing to diagnose or monitor diseases and conditions that affect the lungs’ ability to transfer oxygen into the bloodstream. Diseases and conditions include:

  • Congenital (present at birth) lung and chest conditions including chest deformities, cystic adenomatoid malformations, pulmonary sequestrations, and congenital lobular emphysema
  • Cystic fibrosis, a genetic disorder that causes thick, sticky mucus build-up in the lungs and other organs
  • Emphysema, a chronic disease in which the alveoli (air sacs in lungs) are gradually destroyed
  • Inflammatory lung conditions including allergic alveolitis, asbestosis, sarcoidosis, and systemic lupus erythematosus (SLE)
  • Lung problems due to premature birth including pulmonary hemorrhage
  • Neuromuscular diseases including muscular dystrophy and amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease)
  • Pulmonary edema, a buildup of fluid in the alveoli (air sacs of the lungs)
  • Pulmonary embolism, a blood clot in a blood vessel of the lungs 
  • Pulmonary fibrosis, lung scarring due to growth of excessive fibrous tissue in the lungs
  • Pulmonary hypertension, high blood pressure in the blood vessels of the lungs

Who performs lung diffusion capacity?

The following specialists perform or order lung diffusion capacity testing:

  • Pulmonary function technologists specialize in performing pulmonary function tests.
  • Pulmonologists and pediatric pulmonologists specialize in the medical care of people with breathing problems and diseases and conditions of the lungs. Pediatric pulmonologists further specialize in treating infants, children and adolescents.
  • Thoracic surgeons specialize in the surgical treatment of diseases of the chest, including the blood vessels, heart, lungs and esophagus. Thoracic surgeons may also be known as cardiothoracic surgeons.
  • Neonatologists specialize in caring for premature babies and full-term newborn babies with injuries, illnesses, or birth defects.
  • Congenital cardiac surgeons specialize in the surgical treatment of heart defects present at birth.

How is lung diffusion capacity performed?

Your lung diffusion capacity will be performed in a hospital. The test takes 15-20 minutes and generally involves these steps:&