Lung diffusion capacity: what does this breathing test assess?

New breathlessness without distress needs medical assessment the same day. Call 15 or 112 in France for short shallow breathing at 30 or more per minute even while seated, visible effort to breathe, difficulty speaking, blue lips or fingers, sweating, altered alertness, a very fast pulse (at least 120), a weak or slow pulse, or falling blood pressure. With breathlessness, chest pain, palpitations, leg swelling, recent weight gain or facial swelling are also emergency signs.

Lung diffusion capacity is a test that helps assess gas exchange between the air sacs of the lungs and the blood. It can complement an assessment arranged by a respiratory specialist in different lung conditions.

It answers a different question from spirometry, which measures air volumes moved and breathing flow rates. Depending on your situation, several respiratory tests may be proposed and interpreted together.

At Nancy University Hospital, the test uses a mouthpiece and nose clip. The person follows breathing instructions involving very small quantities of gases. Ask the service carrying out your test to explain its planned procedure.

Tell the centre about recent eye surgery, unstable cardiovascular disease or a recent pneumothorax: Nancy University Hospital lists these as contraindications to its test. Also report recent infection and your medicines for personal instructions.

During the test, tell the team about any discomfort or fatigue. Afterwards, ask who will explain the results and how they relate to the other tests; a single number is not a reason to change treatment yourself.