17966 Pulmonary Function Testing

Overview

Pulmonary function testing (often shortened to PFT) is a group of simple breathing tests. They measure how well your lungs are working — how much air they can hold, how quickly you can blow air out, and how well oxygen passes from your lungs into your blood. "Pulmonary" just means "to do with the lungs." The tests do not hurt, and they give your doctor a clear picture of your breathing that a stethoscope alone cannot show.

Yes, very common. Lung function tests are among the most frequently ordered breathing tests worldwide and are a routine part of asthma and COPD (chronic obstructive pulmonary disease) care.

Anyone with ongoing breathing symptoms may be offered these tests. That includes people with a cough or breathlessness, people with known lung conditions such as asthma, COPD or cystic fibrosis, people whose jobs expose them to dust or fumes, people being assessed before chest or abdominal surgery, and sometimes people taking medicines that need lung monitoring.

Symptoms

Common symptoms

• Breathlessness — especially when walking, climbing stairs or exercising — is the most common reason people are sent for lung function tests.
• A cough that has lasted weeks or keeps coming back, with or without phlegm.
• Wheezing — a whistling sound when you breathe, usually on breathing out.
• A tight or heavy feeling in the chest.
• Needing to stop and catch your breath more than you used to.
• Frequent chest infections, or a cough that changes in character.

Symptoms in children

• Young children cannot always manage the forceful blowing the test needs. Most children can do it reliably from about 6 years old; younger children may be coached with games, or your clinic may suggest other tests.
• In children, the tests are often used to check asthma control or to look into a persistent cough or breathlessness.
• Being patient and practising at home with a pretend mouthpiece can help a child feel more confident on the day.

Symptoms in older adults

• Breathlessness may be put down to "just getting older" — but it is still worth checking, because treatment can help.
• Some older adults get tired or light-headed during the forceful breathing. The technician will let you rest as often as you need and you can do most tests sitting down.
• If you have arthritis, a sore mouth or dentures that feel loose, tell the technician — there are ways to make the test more comfortable.
• Bring a list of all your medicines, including inhalers and anything you buy over the counter.

Causes

Main causes

• Your doctor may arrange a pulmonary function test to look into unexplained breathlessness, cough or wheeze.
• To help diagnose a condition such as asthma, COPD, or scarring of the lung tissue.
• To check how well a known lung condition is controlled, or how well treatment is working.
• To measure lung strength and reserve before surgery, or as part of an assessment for lung surgery or transplant.
• To monitor people whose work exposes them to dust, fumes or other lung irritants.
• To check lung health when someone is taking a medicine that can affect the lungs.
• To see whether breathing difficulty is coming from the lungs or from another cause, such as the heart or being out of condition.

Risk factors

• A history of smoking, or growing up in a smoky home.
• Working with dust, asbestos, silica, fumes or birds and animals.
• A personal or family history of asthma, eczema or allergies.
• Being born prematurely, or having frequent chest infections as a child.
• Living with obesity, which can make breathlessness more noticeable.
• Long-term heartburn or reflux, which can irritate the airways.

When to see a doctor

See a doctor urgently if:

• Call your local emergency number if you have severe breathlessness, blue lips, chest pain, confusion or fainting. Do not wait for a routine appointment.
• Contact your doctor the same day if you are coughing up blood, your breathlessness is quickly worsening, or a flare-up is not responding to your usual plan.
• Seek prompt advice if you have a new fever with a worsening cough, or if you feel faint during normal activity.

Book a routine appointment if:

• Book a routine appointment if a cough has lasted more than three weeks, or keeps coming back.
• See your doctor if you get breathless doing things that used to be easy for you.
• Ask for a review if you are using a reliever inhaler more often than usual, or waking at night with breathing symptoms.
• Mention any family history of lung disease or a job with dust or fume exposure — it may change what tests are suggested.

Diagnosis

Pulmonary function testing is the test itself rather than a diagnosis. On the day, a trained technician will explain each step. You will sit upright, put a clip on your nose so all air goes through your mouth, and breathe into a mouthpiece. For most tests you take a deep breath in and then blow out as hard and as long as you can. You will usually repeat this several times so the machine can be sure the effort was good. Some parts involve breathing normally for a while, or sitting in a small clear booth so the pressure changes can be measured. The technician cannot tell you your results — a lung specialist or your own doctor will interpret them alongside your history and examination.

Tests that may be done

• Spirometry — the main test. You blow out as hard and fast as you can into a machine, which measures how much air you can push out in the first second and in total.
• Bronchodilator response — you repeat the blowing test after inhaling a reliever medicine through a spacer to see whether your airways open up.
• Lung volumes — measures the total amount of air your lungs can hold, sometimes using a clear sealed booth (a "body box") or a special gas you breathe in.
• Gas transfer (also called diffusion or DLCO) — a very small, safe amount of a tracer gas is breathed in to see how well oxygen passes into your bloodstream.
• Pulse oximetry — a clip on your finger checks the oxygen level in your blood. Quick and painless.
• Exercise or walk tests — measuring your breathing and oxygen while you walk for a set time, to see how your lungs cope with activity.
• Blood gas test — a small blood sample, usually from the wrist, to check oxygen and carbon dioxide levels if more detail is needed.

What to expect at your appointment

The test is not painful, but it can be tiring and you may feel a little light-headed or cough afterwards. You will get rests between attempts. Your clinic will send you instructions in advance. In general, you may be asked not to smoke for 24 hours beforehand, to avoid a heavy meal in the two hours before, and to avoid caffeine on the day. You may also be asked to hold off certain inhalers for a set number of hours — always follow the instructions your clinic gives you and never stop your regular medicine without being told to. Wear loose, comfortable clothing. Tell the technician if you feel unwell, dizzy or have chest pain at any point; the test can be stopped at any time.

Treatment

The test itself does not treat anything — it guides treatment. Once your results are known, your doctor can explain what is happening in your lungs and agree a plan with you. For many people that plan is simple: the right inhaler technique, a written action plan, staying active and avoiding triggers. For others it may include tablets, breathing exercises or a supervised exercise and education programme for people with lung disease. Your results also help show whether your current treatment is working, so it can be adjusted if needed.

Self-care at home

• Prepare for the test as instructed — it makes the results more reliable and may save you a repeat visit.
• Keep a short diary of when your breathing is worse, what seems to trigger it, and how often you use relief medicine. Bring it with you.
• Learn and practise good inhaler technique with your pharmacist or nurse — it makes a bigger difference than most people expect.
• Stop smoking if you smoke. Ask your doctor or pharmacist for support; it is the single biggest thing you can do for your lungs.
• Stay physically active within your comfort zone, and pace yourself on bad days rather than doing too much at once.
• Keep your follow-up appointments so changes can be picked up early.

Medical treatments

Treatment depends entirely on what the tests show. Options your doctor may discuss include inhaled medicines that open the airways or reduce inflammation, tablets in some conditions, a course of steroid tablets for a flare-up, oxygen therapy at home for low oxygen levels, breathing and clearing techniques taught by a physiotherapist, and a structured exercise and education programme for people with long-term lung disease. Some people are referred to a specialist lung service. Your doctor will explain the choices, benefits and side effects, and will not start any medicine without discussing it with you first.

When is surgery considered?

Surgery is only relevant for a small number of people. Lung function results are used to check whether someone is strong enough for an operation, and sometimes to plan lung surgery for a specific problem such as a collapsed lung, a damaged area of lung, or as part of assessment for a lung transplant. For most people having a lung function test, surgery is not part of the picture at all.

Living with this condition

If your tests lead to a diagnosis, life usually carries on much as before, with a few adjustments. Many people find that understanding their numbers is reassuring — it turns a vague worry into something that can be measured and managed. A written action plan from your doctor, telling you what to do when symptoms get worse, is one of the most useful things you can have. Learn the early signs of a flare-up, keep your medicines where you can reach them, and let people close to you know how they can help.

Lifestyle tips

• Avoid cigarette smoke, including second-hand smoke, and ask for help to quit if you smoke.
• Try to stay active — walking, swimming or cycling at your own pace keeps your heart and lungs working well.
• Avoid breathing in fumes, strong cleaning products, dust or smoke from open fires where you can.
• Keep rooms ventilated and avoid damp and mould.
• Take your medicines as agreed and check your inhaler technique at every review.
• Keep up with recommended vaccinations — ask your doctor or pharmacist what is advised for you.

Diet and exercise

There is no special diet for lung health, but eating well helps you keep strength and a healthy weight — being very overweight or underweight both make breathing harder. Aim for regular meals with plenty of vegetables, fruit, whole grains and protein. If big meals leave you breathless, try smaller ones more often. For exercise, start gently and build up. Walking, stationary cycling, and simple strength work with light weights or resistance bands are all good. Stop and rest if you feel dizzy or very breathless, and ask your doctor or a physiotherapist what is safe for you. A supervised pulmonary rehabilitation programme is a great option for many people with long-term lung conditions.

Mental health and emotional wellbeing

Breathlessness and worry feed each other: feeling short of breath can make you anxious, and anxiety can make you feel more breathless. This is very common and nothing to be embarrassed about. Slow, steady breathing exercises, pacing your activities and talking to someone about your worries all help. If low mood or anxiety is affecting your sleep, appetite or daily life, please tell your doctor — effective support is available. If you ever have thoughts of harming yourself, contact your local emergency number or a crisis line in your country straight away, or go to your nearest emergency department.

Prevention

You cannot always prevent needing a lung function test, but you can protect your lungs. Not smoking and avoiding other people's smoke is the most important step. Avoiding dust and fumes at work — with proper masks and ventilation — and at home also matters. Keeping asthma or other lung conditions well controlled, treating reflux, and staying active all help keep your lungs in the best shape possible.

Vaccines

Vaccination reduces the chance of chest infections that can damage lungs or trigger flare-ups. Ask your doctor or pharmacist which vaccinations are recommended for you — commonly this includes yearly flu vaccination and COVID-19 vaccination, and sometimes vaccination against pneumococcal infection, especially if you have a long-term lung condition.

Screening programmes

Pulmonary function testing is not a general screening test for the public. It is used when symptoms suggest a problem, when a condition is already known, before some operations, or for workplace health surveillance in jobs with lung irritants. If you have a high-risk job or a strong family history of lung disease, ask your doctor whether monitoring is right for you.

Complications

If left untreated

• The test itself is very safe. Short-term effects are mild: coughing, tiredness, dizziness or light-headedness, a dry throat, or rarely fainting. These usually pass within minutes, and you can rest as needed.
• The bigger risk is not having the test: a lung condition can go undiagnosed or untreated and slowly get worse.
• Untreated breathing problems can lead to more infections, poorer sleep and fitness, reduced ability to work or exercise, and more frequent hospital visits.
• Missing out on treatment can also mean missing out on simple things that would make you feel considerably better.

Long-term outlook

The outlook is generally good. Most people who have lung function tests get clear answers, and many conditions found this way respond well to treatment. Knowing your numbers gives you and your doctor a baseline to compare against, so changes are spotted early and your plan can be adjusted. Many people with lung conditions live full, active lives with the right support — and the test is the first step in getting that support.

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