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What is pulmonary diffusion?

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Written in association with: Top Doctors editorialSources: Top Doctors GB
Published: 23/08/2017 Edited by: on 17/05/2025

What is pulmonary diffusion?

Pulmonary diffusion of carbon monoxide (DLCO) or carbon monoxide transfer is a diagnostic test that measures how gaseous exchange is performed in the lungs.

This Pneumology test determines the degree of efficiency with which oxygen crosses the alveolar walls and is transferred from the lungs to the blood.

The pulmonary capillary bed is a very fine barrier which is connected to the alveoli of the lungs and functions as a filter for the blood. In normal circumstances, there should be no problems in this gaseous exchange: the oxygen (O2) of the inspired air is absorbed well and passes into the blood, while the carbon dioxide (CO2) passes from the blood to the alveoli to be exhaled.

In general, if this does not occur efficiently, and oxygen exchange between the lungs and blood is abnormal, it may be a symptom of serious diseases such as pulmonary fibrosis, pulmonary embolism or hypertension, asthma, emphysema, or other pulmonary blood vessel problems.

How does the pulmonary diffusion test work?

A pulmonary diffusion test should be performed by highly qualified specialists in the field of pulmonology, as specially designed equipment is needed.

The pulmonary diffusion test is not only useful for detecting problems, but can also be used for monitoring and evaluating the progression of a disease.

Before proceeding with the examination, it is very important for the doctor to be aware of the patient's basic data (sex, age, height, weight). It is also essential to know the levels of haemoglobin in the patient's blood, because sometimes, such as in the case of a patient with anaemia, the values ​​of the diffusion test are affected.

In general, the test lasts between five to ten minutes, and involves the patient wearing a tight-fitting mouthpiece and a nose clip. The patient inhales a mixture of gases with a small concentration of carbon monoxide, holding their breath for ten seconds and then expeliing the air, enabling the medical team to analyse and measure the difference in the concentration of inhaled and exhaled gases.

When is it necessary to do a pulmonary diffusion test?

This is the most useful test for the diagnosis and treatment of pulmonary emphysema (COPD), a disease that develops in smokers. In fact, pulmonologists recommend lung screening for all smokers over 35 years of age who smoke an average of one pack per day over the last ten years. It is also advised in cases of interstitial diseases, lung diseases and in the assessment of surgical risk in cases of lung surgery.

The pulmonary diffusion test is very useful for diagnosing certain lung diseases and for monitoring the condition of people with established lung disease. It is simple and easy to perform and has no side effects.

Once the problem is detected, the treatment of the disease in question can begin.

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