Body plethysmography (lung volume test)
A breathing test done inside a clear, sealed booth that measures the total amount of air your lungs can hold, including air left behind after breathing out.
✓ Medically reviewed by a GMC-registered consultant · last reviewed September 2026 · next review September 2027 · how we review
In short
- It measures the total air your lungs hold, including trapped air that simpler tests miss, while you sit in a clear sealed booth.
- The booth is see-through and you can be seen and talk to the operator throughout, but some people find the enclosed space uncomfortable.
- It does not diagnose a specific disease on its own; results are read with your symptoms and other tests.
- It depends on following instructions and good technique, so manoeuvres are repeated to get reliable results.
A plain-English summary. The detail — including risks and recovery — is below.
At a glance
A general guide. Your specialist will give you advice for your situation.
Accurately measures total lung capacity and trapped air that simpler tests cannot
When someone cannot tolerate sitting in the enclosed booth despite support.
You sit in the clear booth and do several breathing manoeuvres with coaching. Tell the operator at any time if you feel unwell or want to come out.
Reliable, quality-checked results interpreted by a trained professional.
You sit in the clear booth and do several breathing manoeuvres with coaching. Tell the operator at any time if you...
Any light-headedness or cough usually settles within minutes, and most people resume normal activities straight...
The measurements are interpreted by a specialist and usually discussed at a clinic appointment or by letter...
Depending on the results, you may have further tests, start or change treatment, or be monitored over time.
What is body plethysmography?
Body plethysmography is a breathing test that measures how much air your lungs can hold, including the air that stays behind after you breathe out as far as you can. It is done while you sit inside a clear, sealed booth, sometimes called a 'body box'.
You breathe through a mouthpiece, and at one point you gently pant against a brief, closed shutter. By measuring the small pressure changes inside the sealed booth as you breathe, the machine works out your lung volumes — including total lung capacity and the residual volume left after a full breath out. It can also measure how much resistance there is in your airways.
This test is especially good at measuring trapped air that simpler tests cannot, which is why it is often used alongside spirometry and gas transfer to assess conditions such as COPD, asthma and restrictive lung problems.
It measures how the lungs are working on the day. It does not name a specific disease by itself; results are interpreted alongside your symptoms, examination and other tests.
Types, options & approaches
There may be different ways to do this. The right approach depends on the clinical question and your circumstances.
Plethysmography vs spirometry
| Body plethysmography | Spirometry | |
|---|---|---|
| What it measures | Total lung volume and trapped air | Airflow in and out |
| Trapped air | Measured well | Not measured |
| Setting | Sealed booth ('body box') | Open chair |
| When used | When lung volumes are needed | First-line airflow test |
The two are complementary. Spirometry measures airflow; plethysmography measures how much air the lungs hold, including air that does not move out.
Preparing for your test
- Follow any instructions on your appointment letter; you can usually take your normal inhalers and medicines.
- Avoid smoking or vaping shortly before, and avoid a heavy meal, vigorous exercise and alcohol just beforehand.
- Wear loose clothing that allows comfortable, deep breathing.
- Tell the team if you have a recent chest infection, as you may be asked to reschedule.
- If you find enclosed spaces difficult, mention it in advance — the booth is clear and you can be seen and heard throughout.
- Mention recent surgery, a heart attack, stroke or eye surgery, which may affect whether the test goes ahead.
- Bring your inhalers and a list of medicines.
What happens
A trained physiologist explains the test and helps you into the clear booth, where you sit on a chair. The door is closed so the booth is sealed, but it is see-through and the operator can see you, talk to you and let you out at any time.
You breathe through a mouthpiece with a soft clip on your nose. You breathe normally, then follow instructions to breathe in different ways, including a gentle panting against a brief, closed shutter. This lets the machine measure your lung volumes from the tiny pressure changes in the booth. The manoeuvres are usually repeated to get reliable results, with coaching throughout.
The test typically takes around 15–30 minutes, often as part of a fuller set of lung function tests. The measurements are recorded and interpreted afterwards by a specialist, alongside your symptoms and history.
Is this test right for me?
A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.
May not be suitable if…
- When someone cannot tolerate sitting in the enclosed booth despite support.
- When someone cannot follow the breathing instructions, making reliable results impossible.
- As a stand-alone way to diagnose a specific disease without considering symptoms and other tests.
- During an acute chest infection, which can distort results.
Delay or rearrange if…
- You have a current chest infection or are acutely unwell.
- You have had recent surgery or a cardiovascular event that means breathing manoeuvres should wait.
- You are too anxious or unwell on the day to complete the test.
- Key information or previous results are missing and would change interpretation.
Alternatives to discuss
- Gas-dilution methods of measuring lung volumes for people who cannot use the booth.
- Spirometry alone if only airflow information is needed.
- Imaging such as a chest X-ray or CT scan for structural questions.
- Clinical assessment alone where a test would not change management.
Before you decide
Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.
What matters most to me?
Think about symptoms, daily life, work, caring responsibilities, sport, fertility, travel, appearance and anxiety — the right choice depends on your priorities, not just the medical facts.
What are all my options?
Ask about waiting, monitoring, medicines, rehabilitation, a smaller or larger procedure, a different test, NHS referral, or a second opinion where that would help.
What would make me pause?
Active infection, pregnancy, unstable medical problems, smoking, medicines that increase bleeding, poor support at home, or feeling pressured are all reasons to slow down and get tailored advice.
What happens if I do nothing today?
For some problems, waiting is safe; for others, delay can make treatment harder. A good consultation should explain the trade-off in plain English.
Benefits
- Accurately measures total lung capacity and trapped air that simpler tests cannot
- Helps tell apart obstructive conditions (such as COPD) and restrictive ones
- Can measure airway resistance, adding information about narrowing
- Builds a fuller picture when combined with spirometry and gas transfer
- Helps monitor a condition or the effect of treatment over time
- Non-invasive and does not use radiation
Risks & complications
- Feeling enclosed or mildly claustrophobic in the booth
- Light-headedness or breathlessness for a short time after the manoeuvres
- Coughing during or after the test
- Needing to repeat manoeuvres if results are inconsistent
- Anxiety in the booth that means stopping and trying again, or being unable to complete it
- Headache or tiredness shortly afterwards
- Inconclusive results needing repeat or further tests
- Fainting (the most commonly reported notable event in lung function testing)
- Difficulty completing the test in people who cannot tolerate the enclosed space or follow the manoeuvres
Body plethysmography is a safe, non-invasive test. The main practical issue is comfort: some people feel enclosed in the sealed booth, although it is clear and you can be seen and let out at any time. Results depend on following instructions and good technique, so manoeuvres are repeated. Tell the team in advance if you find enclosed spaces difficult, so they can talk you through it or consider an alternative way of measuring lung volumes.
Published figures to discuss
Body plethysmography is safe and non-invasive, and serious complications are rare. The main issue is tolerability rather than danger: some people find the sealed booth uncomfortable. Because adverse events are so uncommon, robust complication percentages are not well established, so we describe risks qualitatively. The more relevant uncertainty is that results depend on technique and on being able to complete the manoeuvres in the booth.
| Figure | Reported range | How to interpret it | Source / confidence |
|---|---|---|---|
| Physical harm from the test | Very low | It is non-invasive and does not involve radiation, injections or sedating medicine. | Guide sourcesClinical context |
| Claustrophobia, dizziness or breathlessness in the booth | Recognised | Patients can stop if they feel unwell. Anxiety and poor seal around the mouthpiece can reduce test quality. | Guide sourcesClinical context |
| Technically invalid or misleading result | Recognised | Leaks, poor effort, recent bronchodilator use, acute illness and suboptimal coaching can all distort lung-volume measurements. | Guide sourcesClinical context |
| False reassurance from normal lung volumes | Recognised | Normal volumes do not rule out asthma, early interstitial lung disease, pulmonary vascular disease or non-lung causes of breathlessness. | Guide sourcesClinical context |
These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.
What happens afterwards
There is usually no physical recovery — most people feel normal within minutes. 'Afterwards' mainly means waiting for the results to be interpreted.
- Brief light-headedness or breathlessness that quickly passes
- A little coughing after the manoeuvres
- Feeling slightly tired from the effort for a short while
- Waiting a few days to weeks for the results to be explained
Aftercare
- Resume your normal inhalers and medicines as advised once the test is done.
- Have a drink and rest for a few minutes if you feel light-headed.
- Ask when and how you will get your results.
- Note any symptoms to discuss when the results are explained.
- Attend any follow-up appointment or further tests arranged.
- Contact the clinic if you feel persistently unwell afterwards, which is unusual.
- Appointment instructions checked
- Note if you find enclosed spaces difficult, mentioned in advance
- Note of recent illness, surgery or heart problems
- Inhalers and medicines list brought along
- Avoided smoking, heavy meals and vigorous exercise beforehand
- Questions about what the result will show
- Clear plan for how results will be shared
⚠ Get urgent help if…
- Chest pain during or after the test — tell the operator immediately or seek urgent help
- Severe or persistent breathlessness that does not settle
- Fainting or feeling you might pass out
- Severe anxiety or panic in the booth — tell the operator, who can let you out
- Coughing up blood
- Any symptom that feels serious — a breathing test should not leave you unwell
Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.
General guidance — it doesn't replace the specific advice your specialist gives you.
Results & realistic expectations
A 'good' result is a set of reliable measurements of your lung volumes (and sometimes airway resistance) that, alongside your symptoms, examination and other tests, help your specialist understand how your lungs are working. The pattern can suggest whether the lungs are over-inflated with trapped air, restricted, or normal.
The test does not name a specific disease on its own, and a normal result does not rule out every lung condition. It is one important piece of the picture, interpreted together with spirometry, gas transfer, imaging and your symptoms. Poor technique or difficulty tolerating the booth can affect the result, which is why it is repeated and quality-checked.
The results reflect your lungs on the day of testing. Lung volumes change over time and with treatment, so the test is often repeated to monitor a condition. How often depends on your diagnosis and stability, which your clinician will advise.
Related tests, treatments or support
Body plethysmography is usually combined with spirometry and a gas transfer test in one visit to give a full picture of lung function, and sometimes with a chest X-ray or CT scan and blood tests, depending on your symptoms.
Follow-up & long-term care
Results are interpreted by a specialist and usually discussed at a clinic appointment or by letter. Depending on the findings, you may have further tests, start or change treatment, or be reviewed at intervals. Any abnormal result should have a clear plan for what happens next.
- Repeat the test as advised to monitor a known condition
- Use inhalers and treatments as prescribed between tests
- Tell the team about new symptoms before a monitoring test
- Keep previous results so changes over time can be compared
Repeat, follow-on and what comes next
- Manoeuvres are repeated in one sitting to get reliable, quality-checked results.
- The test may need redoing if technique or tolerance affected the results.
- An alternative method may be used if someone cannot complete the booth test.
- Monitoring tests are repeated over time to track a condition.
Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.
What good aftercare looks like
- Reliable, quality-checked results interpreted by a trained professional.
- A clear explanation of what the result means alongside your symptoms.
- A plan for any further tests, treatment or monitoring.
- Results shared with your GP or referring clinician.
- A contact route if you feel unwell afterwards, which is unusual.
What affects the cost
Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:
- Whether the test is done alone or as part of full lung function testing
- Where it is done and the equipment used
- Who interprets and reports the results
- Whether it is combined with imaging or blood tests
- Any follow-up consultation to discuss the results
- Whether repeat tests are needed for monitoring
- Whether the test is standalone or part of a full lung function package
- The fee for the test and for interpretation and reporting
- Whether a consultation to discuss results is included
- Cost of any additional tests or imaging if recommended
- What happens, and what it costs, if the test must be repeated
- How and when you receive your results
- Whether results are shared with your GP or referring clinician
On the NHS? Body plethysmography is available on the NHS when clinically indicated, usually in a hospital lung function laboratory; private testing is used mainly for speed or convenience.
You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.
Consent traps and marketing red flags
These are not small details. They are often where patients lose choice, time to reflect, or realistic expectations.
Consent traps
- Not being warned that the test is done in an enclosed booth, which some find difficult.
- Not being told that technique and cooperation strongly affect the result.
- Assuming a normal result rules out all lung disease.
- No clear plan for who interprets the result and how you will be told.
- No mention of alternative ways to measure lung volumes if the booth is not tolerated.
Marketing red flags
- Lung function testing sold as a complete 'lung MOT' that rules everything out.
- Results given without specialist interpretation or clinical context.
- Claims that the test diagnoses a specific disease with certainty.
- Bundled testing pushed regardless of symptoms.
- No mention of quality checks or what happens if the booth cannot be tolerated.
Choosing a specialist safely
- Check the specialist is on the GMC Specialist Register for this area.
- Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
- You're entitled to time to consider and to have your questions answered before you agree — the specialist who looks after you should explain it, not a salesperson.
- Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
- You're entitled to your total cost in writing — including any follow-up — before you decide.
Questions to ask your medical professional
Take this to your consultation. A good specialist will welcome every one of these.
- What is this test looking for in my case?
- Is there anything I need to do or avoid beforehand?
- What will the result change about my diagnosis or treatment?
- What happens if the result is normal, abnormal or inconclusive?
- What can I do if I find the booth difficult?
- When and how will I get my results, and who explains them?
- Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
- Will you be the specialist who carries out my test, and who looks after me afterwards?
- What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
- What does a realistic result look like — and what can this test not achieve?
- What are my options, including waiting, doing nothing for now, or choosing a different approach?
- Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
- What is the total cost in writing, including any follow-ups, and how much time do I have to decide?
Frequently asked questions
Will I feel trapped in the booth?
How is this different from spirometry?
Is the test uncomfortable?
Will it diagnose my condition?
How long does it take?
Why do I have to repeat the manoeuvres?
Is it available on the NHS?
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How we made this page
Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →
Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.
Sources & standards: Asthma + Lung UK — Lung volume test (body plethysmography) Body Plethysmography — StatPearls (NCBI) Royal Free London — Lung function tests: a guide Pulmonary Function Tests — StatPearls (NCBI) ARTP — lung function testing resources
Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.
Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.
Related guides: Spirometry (lung function test) · Full lung function tests (gas transfer) · Respiratory consultation · Bronchial and transbronchial biopsy · Bronchial challenge (provocation) test