15445 Dlco

Overview

DLCO stands for 'diffusing capacity of the lungs for carbon monoxide'. It is a simple breathing test that shows how well oxygen moves from the air in your lungs into your blood. You breathe in a small, safe amount of a test gas through a mouthpiece, hold your breath for about 10 seconds, and then breathe out. The machine measures how much of the gas your lungs took up. A low result means oxygen is not crossing into your blood as easily as it should. A DLCO test is usually done as part of a group of breathing tests called lung function tests, sometimes on the same day as spirometry (a test that measures how much air you can blow out and how fast).

Yes. DLCO is a routine and very common test. It is done millions of times a year in hospitals and clinics around the world, usually alongside other breathing tests.

Anyone can be asked to have a DLCO test. It is most often offered to adults who feel short of breath, have a persistent cough, or already know they have a lung condition. It is also used to check lung health before certain operations or treatments, and to monitor people whose lungs may be affected by medicines or by conditions such as Rheumatoid arthritis. Children can have the test too, usually from around 5 to 7 years old, when they can follow the breathing instructions.

Symptoms

Common symptoms

• Feeling short of breath when walking, climbing stairs or doing everyday tasks
• A cough that does not go away, sometimes with phlegm
• Wheezing or a whistling sound when breathing
• Chest tightness
• Unusual tiredness or low energy during activity
• Breathlessness that has slowly become worse over months
• A dry cough alongside a known lung condition such as pulmonary fibrosis (scarring of the lung tissue)

Symptoms in children

• Getting out of breath more quickly than other children during play or sport
• A cough that keeps coming back, or a cough at night
• Frequent chest infections
• Poor weight gain or feeding difficulties in babies and toddlers
• Breathing faster than usual, or pulling in of the skin between the ribs when breathing

Symptoms in older adults

• Breathlessness doing tasks that used to feel easy, such as dressing or making a cup of tea
• Reduced stamina or needing to rest more often
• A long-standing cough or repeated chest infections
• Feeling more tired than usual, which can be put down to age but is worth checking
• Breathlessness that is worse when lying flat

Causes

Main causes

• This test does not have 'causes' in the usual sense. It is a measurement, and an unusual result points to something affecting the lungs or blood.
• Lung damage from smoking, such as emphysema (where the tiny air sacs are damaged), is a common reason for a low result.
• Scarring of the lung tissue, called pulmonary fibrosis, lowers the result because the scarred tissue is thicker.
• Conditions affecting the blood vessels in the lungs, such as pulmonary hypertension (high blood pressure in the lung arteries) or a blood clot in the lung, can lower the result.
• Anaemia (a low red blood cell count) can lower the result, because red blood cells carry the oxygen.
• Other things that can affect the reading include recent smoking, alcohol, a very full stomach, heavy exercise just before the test, and how well the breath is held during the test.

Risk factors

• Smoking or a history of smoking, including passive smoking
• Working with dusts, fumes or fibres, such as asbestos, silica or certain farm and building materials
• A family history of lung disease, such as pulmonary fibrosis
• Long-standing asthma or COPD (chronic obstructive pulmonary disease)
• Certain medical conditions that can affect the lungs, such as rheumatoid arthritis or other autoimmune conditions
• Some medical treatments that can affect the lungs over time — your care team will discuss this if it applies to you
• Living at high altitude, which changes the expected result

When to see a doctor

See a doctor urgently if:

• You have sudden or severe breathlessness, chest pain, or you are coughing up blood — call your local emergency number immediately.
• Your breathing has got noticeably worse over hours rather than weeks.
• You have a fever with a cough and feel unwell.
• You are unable to do your usual daily activities because of breathlessness.

Book a routine appointment if:

• You have been short of breath with activity for more than a few weeks.
• You have a cough that has lasted more than three weeks.
• You have been given a DLCO result and do not understand what it means — ask the team who ordered the test.
• You have a known lung condition and your symptoms are slowly changing.
• You are being asked to have the test before surgery or a new treatment and want to know what to expect.

Diagnosis

A DLCO test is a measurement, not a diagnosis on its own. You will be asked to sit comfortably, wear a nose clip, and breathe through a mouthpiece. After a few normal breaths, you take a deep breath of a test gas mixture, hold it for about 10 seconds, then breathe out. This is usually repeated two or three times to get a reliable reading. The machine prints a number, which is compared with the expected value for your age, height and sex. Your doctor puts that number together with your symptoms, your medical history, a physical examination and other tests to work out what is going on.

Tests that may be done

• Spirometry — blowing into a machine to measure how much air you can breathe out and how fast
• Lung volume measurement — to see how much air your lungs can hold
• Pulse oximetry — a small clip on your finger that estimates the oxygen level in your blood
• A blood test to check your red blood cell count, which affects the DLCO reading
• Chest X-ray or CT scan of the chest, if your doctor needs a picture of your lungs
• An arterial blood gas test in some cases, which measures oxygen and carbon dioxide in a small sample of blood
• A walking or exercise test to see how your breathing responds to activity

What to expect at your appointment

The whole visit often takes 30 to 60 minutes, and the DLCO part itself takes only a few minutes. It is not painful and you can go home straight afterwards. You may be asked not to smoke for at least a few hours beforehand, to avoid a heavy meal just before, and to avoid strenuous exercise on the day, because these can affect the result. Tell the person doing the test if you feel dizzy, if you have recently had a chest infection, or if you use oxygen at home. Results are usually sent to the doctor who referred you, and you may be asked to come back to talk them through.

Treatment

The DLCO test does not need treatment — it is a measurement. Any treatment comes from what the test finds, together with your other results. If your lungs are healthy, no treatment is needed. If the test points to a lung or blood condition, your healthcare team will explain the options and build a plan with you. There is a lot that can be done to ease breathlessness, protect your lungs and keep you active, whatever the cause.

Self-care at home

• Follow the preparation instructions for the test — for example, no smoking or heavy meals beforehand.
• Keep a note of your symptoms, when they happen and what makes them better or worse, to discuss at your appointments.
• Stay as active as you comfortably can — regular gentle movement helps your heart and lungs work better.
• If you smoke, ask your healthcare provider for help to stop. This is the single biggest thing most people can do for their lung health.
• Keep up with recommended vaccinations and ask your pharmacist or clinic which ones apply to you.
• Avoid breathing in dust, fumes, smoke and strong chemicals where possible, and use protective equipment at work if needed.
• Learn breathing and pacing techniques — a respiratory physiotherapist can teach these and they really help with breathlessness.

Medical treatments

Treatment depends entirely on what the test shows and is decided by your healthcare team. For many lung conditions, treatment includes inhaled medicines that open the airways or reduce inflammation, tablets to control symptoms, and pulmonary rehabilitation — a structured programme of exercise and education that helps people breathe more easily and stay active. Some conditions, such as scarring of the lungs or high blood pressure in the lung arteries, need specialist care and specific treatments chosen by a lung specialist. If anaemia is found, that will be looked into and treated. Oxygen therapy may be offered to some people with low oxygen levels. Everyone with a lung condition should be offered a written action plan for flare-ups.

When is surgery considered?

Surgery is not part of a DLCO test. However, a DLCO result is sometimes used to help judge whether someone is fit enough for an operation, especially lung surgery or major abdominal surgery. Rarely, surgery or a lung transplant may be an option for certain advanced lung conditions, and a specialist team would discuss this with you in detail.

Living with this condition

Most people have a DLCO test, get their result, and carry on with normal life. If the test shows a lung condition, day-to-day life can still be good. The key is to pace yourself, plan activities around your best times of day, keep your home smoke-free, and know what to do if your breathing worsens. Many people find that a small amount of planning — such as keeping shopping bags light, using a trolley, or taking a rest halfway up the stairs — makes a big difference.

Lifestyle tips

• Stop smoking if you smoke, and keep your home and car smoke-free
• Stay physically active within your limits — walking, swimming or cycling at a gentle pace all help
• Keep rooms well ventilated and avoid wood smoke, strong cleaning products and fumes
• Ask about pulmonary rehabilitation, which many people find life-changing for breathlessness
• Keep to a healthy weight, as extra weight makes breathing harder, and losing weight safely can help
• Plan ahead for travel and ask your healthcare team if you need extra advice about flying or altitude
• Keep your appointments for monitoring — repeat tests show whether things are stable or changing

Diet and exercise

There is no special diet for a DLCO test, and no food will change your lung test result. In general, a balanced diet with plenty of vegetables, fruit, whole grains and enough protein supports your muscles, including the muscles you use to breathe. If breathlessness makes eating tiring, try smaller meals more often and rest before eating. For exercise, aim for regular gentle activity rather than one big effort. Start with short walks and build up slowly. If you have a lung condition, a supervised programme such as pulmonary rehabilitation is the safest and most effective way to get fitter, and your doctor can refer you.

Mental health and emotional wellbeing

It is very normal to feel worried or anxious while waiting for test results, or after being told your lung numbers are not what you hoped. Feeling breathless can itself trigger anxiety, and anxiety can make breathlessness feel worse — a difficult loop. These feelings are common and treatable. Breathing techniques, relaxation, talking to friends and family, and professional support all help. If low mood or worry is affecting your sleep, appetite or daily life, please tell your doctor. If you ever feel you cannot cope or have thoughts of harming yourself, contact your local emergency number or a crisis line in your country straight away — you deserve support and you do not have to manage alone.

Prevention

You cannot prevent the need for a DLCO test, and you would not want to — it is a useful, safe measurement. What you can do is protect your lungs so that future results stay healthy. Not smoking, or stopping if you do, is the most important step. Avoiding dust, fumes and smoke at home and at work, keeping physically active, and getting recommended vaccinations all help keep your lungs working well.

Vaccines

Vaccination helps prevent the chest infections that can damage lungs and cause flare-ups. Ask your doctor, nurse or pharmacist which vaccinations are recommended for you — commonly discussed ones include yearly flu vaccination, pneumonia vaccination and COVID-19 vaccination, and the advice differs depending on your age and health.

Screening programmes

There is no general screening programme that uses DLCO for the whole population. The test is used when there is a reason — symptoms, a known condition, a workplace exposure, or preparation for surgery or certain treatments. If you have a job with dust or fume exposure, your employer may offer health checks; ask your occupational health service about this.

Complications

If left untreated

• The test itself rarely causes problems. The concern is what an abnormal result might mean if it is not looked into.
• A lung condition that is not recognised may slowly get worse, making breathlessness and tiredness more limiting.
• Low oxygen levels over time can put strain on the heart.
• Untreated anaemia (a low red blood cell count) can cause tiredness, breathlessness and other health problems.
• Missing follow-up tests can mean changes in your lungs are picked up later than they could be.

Long-term outlook

The outlook is generally good, and there is real reason for hope. A DLCO test is a quick, safe way to get useful information early, which means the right support can start sooner. Many people have a normal result and need nothing further. For those with a lung condition, treatments, pulmonary rehabilitation, breathing techniques and lifestyle changes can ease symptoms and help people stay active and independent for a long time. Your healthcare team is there to help you understand your results and plan the next step with you.

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