The DLCO test (Lung Diffusion Testing) measures the exact amount of oxygen that passes from the lungs to the blood.

Do you sometimes have trouble breathing, chest tightness, or a persistent cough? If a doctor says you need to do a test to check your lung function, it's probably a DLCO test. So let's talk about this simply today. This is nothing to be afraid of, it's a very simple test.

Simply put, what is this DLCO test?

The DLCO test is a special test that measures how well oxygen is moving from your lungs into your blood. To be precise, it's one of a number of tests that measure lung function. It can give your doctor a good idea of ​​how healthy and efficient your lungs are.

In this test, a very small, harmless amount of carbon monoxide is added to the air you breathe. Then, the amount of carbon monoxide absorbed from your lungs into your blood is measured. This is called the "diffusing capacity for carbon monoxide," or DLCO for short.

What is 'Diffusion'? How is it important to us?

Imagine, when we breathe, the oxygen in the air goes into our lungs. From there, this oxygen goes to the very small air sacs (alveoli) in the lungs. Around these air sacs are very fine blood vessels (capillaries) spread out like a net.

'Diffusion' refers to the process by which oxygen diffuses from those air sacs into the blood vessels and mixes with the blood. It's like putting a tea bag in a cup of hot water and the tea dissolves into the water. The oxygen that mixes with the blood in this way travels throughout our body and provides energy to our cells.

So, the speed and efficiency with which this oxygen is added to the blood depends on several factors:

• The surface area of ​​the air sacs (alveoli) in your lungs.
• That's how much blood is in the tiny blood vessels (capillaries) around the air sacs.
• The concentration of hemoglobin, the protein that carries oxygen in your blood.
• The thickness of the thin membrane between the air sac and the blood vessel.
• Whether there is unnecessary liquid buildup inside the air vents.

If any of these factors change, the oxygen delivery to the blood may be impaired. That's what the DLCO test is important for detecting.

Why would a doctor recommend this DLCO test?

There are several reasons why a doctor might ask you to have this test. Let's look at the main reasons.

What happens when you take the test?

This is very simple. There is no reason for you to be afraid or worried.

The technician who performs the test will first place a small clip on your nose. Stop breathing through that nose. Then they will tell you to follow these steps:

1. Place your mouth over a mouthpiece: Place your mouth over a mouthpiece connected to a machine and tighten it tightly so that no air can escape.

2. Breathe normally: First, breathe normally, inhaling and exhaling.

3. Take a deep breath: Next, you are told to take a deep breath in as much as possible.

4. Hold your breath: Now you need to hold your breath for about 10 seconds. This is when the carbon monoxide in the special gas mixture is absorbed into your blood.

5. Exhale quickly: Then, you need to exhale all of your breath into the machine at once, quickly.

The machine measures the amount of carbon monoxide left in the air you exhale. From that, they calculate how much has been absorbed into your blood. You may repeat this process once or twice more to get an accurate reading.

Do I need to prepare before the test?

Yes, to get accurate test results, you need to follow a few simple steps. Your doctor will tell you about this. Usually, these are the steps:

• Avoid smoking 4-6 hours before the test.
• If you are using supplemental oxygen, stop it 10 minutes before the test (only if you can do so safely).
• Do not engage in strenuous exercise before the test.

How to understand the test results?

The test results are given as a percentage. This tells you how much your score compares to the DLCO score you should normally have, taking into account factors like your age, height, and gender.

What are the reasons for the decrease in DLCO value?

A low DLCO value means that oxygen is not being transferred from your lungs to your blood efficiently. This can be caused by certain lung or heart conditions. For example:

• Smoking
• Conditions such as COPD (Chronic Obstructive Pulmonary Disease) and Emphysema
• Diseases that affect lung tissue, such as sarcoidosis
• Heart and blood vessel diseases - for example, pulmonary embolism (PE), pulmonary arterial hypertension, congestive heart failure
• Anemia
• Autoimmune disorders - for example, Lupus (SLE), Scleroderma

Can the DLCO value increase?

Yes, in some cases, the DLCO value may be higher than expected. The following may be the reasons for this:

• Asthma
• Obesity
• Exercising before the test
• Living in high mountain areas
• Bleeding inside the lungs
• Blood diseases such as polycythemia vera

If the results are abnormal, what do you do next?

Remember this. The DLCO test is just one piece of the puzzle. Your doctor will combine the results of this test with your symptoms, and the results of other lung tests, such as spirometry, to reach a final diagnosis.

If the results are abnormal, you may be asked to do further tests, perhaps a CT scan, to find out the exact cause. So don't be afraid to think about the results alone. Talk to your doctor about it and follow his or her advice.

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