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Respiratory physiology · London

Spirometry and full pulmonary function tests, read by a consultant respiratory physician.

FEV1, FVC, DLCO, body plethysmography, FeNO. ATS/ERS 2019 standardised, GLI reference equations. From £180 for spirometry, £350-£650 for a full PFT.

A patient performing spirometry with a respiratory physiologist in a London chest unit

What lung function testing measures

Spirometry is the start. A full PFT is the full picture.

The right combination depends on your symptoms, referral question and any suspected diagnosis. Ask your GP or respiratory physician which is right before you book.

Spirometry

FEV1 (forced expiratory volume in one second), FVC (forced vital capacity) and the FEV1/FVC ratio, with the full flow-volume loop. Standardised to ATS/ERS 2019, reported against GLI reference equations. Reversibility testing adds a repeat set 15 minutes after a bronchodilator to look for asthma. Race-neutral or race-specific z-scores are used to define the lower limit of normal (LLN).

Full pulmonary function test (PFT)

Spirometry pre and post bronchodilator, body plethysmography for absolute lung volumes (TLC, RV, FRC), and single-breath carbon monoxide gas transfer (DLCO / TLCO with KCO). Add-ons: MIP, MEP and SNIP mouth pressures for respiratory muscle strength, forced oscillation technique (FOT) for effort-independent airway mechanics, multiple breath washout (MBW) for small-airway ventilation heterogeneity, and FeNO for eosinophilic airway inflammation. Cardiopulmonary exercise testing (CPET) is a separate assessment on its own page.

When it is used

The questions lung function testing answers.

A DLCO drop with normal spirometry is a classic early warning sign. That is one of the many patterns a full PFT is designed to catch.

  • Chronic cough or unexplained breathlessness

    The standard first-line workup when symptoms have not settled with primary care management.

  • Asthma vs COPD differentiation

    Reversibility testing (>12% and >200 mL FEV1 improvement) separates asthma from fixed COPD obstruction.

  • ILD monitoring

    DLCO frequently drops before spirometry changes. Serial testing tracks disease trajectory and treatment response.

  • Pre-operative fitness for lung resection

    FEV1 and DLCO predict post-operative complications and guide surgical planning.

  • Chemotherapy monitoring

    Bleomycin, oxaliplatin and immune checkpoint inhibitors can cause pulmonary toxicity. DLCO is the sensitive marker.

  • Occupational and medical surveillance

    HGV, aviation, commercial diving and hazardous-dust surveillance all require standardised spirometry.

  • Pulmonary hypertension screening

    A reduced DLCO with preserved spirometry is a classic pattern that prompts echo and further workup.

  • FeNO for eosinophilic inflammation

    A raised FeNO supports an eosinophilic asthma phenotype and helps guide inhaled or biologic therapy.

Interpretation basics

What the numbers mean.

Your consultant explains everything in context. This is the short version.

  • Obstruction

    FEV1/FVC below 0.70 or below the lower limit of normal (LLN). Severity graded by FEV1 percent predicted.

  • Reversibility

    A post-bronchodilator FEV1 improvement of >12% and >200 mL supports asthma.

  • Restriction

    A reduced TLC on body plethysmography confirms true restriction. Spirometry alone cannot diagnose it.

  • Impaired gas transfer

    A reduced DLCO points to ILD, emphysema, pulmonary vascular disease or anaemia. Correction with KCO and alveolar volume aids the pattern.

Before your appointment

Preparation matters. Good technique matters more.

The test is technician-dependent. Coaching is what turns a valid effort into a valid result.

  • Short-acting bronchodilators (SABA)

    Withhold for 4 hours before reversibility testing where safe to do so.

  • Long-acting bronchodilators (LABA)

    Withhold for 12 hours before reversibility testing where safe to do so.

  • Ultra long-acting (LAMA)

    Withhold for 24 hours before reversibility testing. Never stop rescue medication without clinical advice.

  • Caffeine

    Avoid tea, coffee and energy drinks for 4 hours before testing.

  • Food and smoking

    No heavy meal for 2 hours. No smoking or vaping for at least 1 hour.

  • Exercise and clothing

    No vigorous exercise for 30 minutes before the appointment. Loose clothing that does not restrict the chest wall.

  • Recent respiratory infection

    Ideally wait 4-6 weeks after a chest infection unless the referrer specifically wants a baseline during illness.

  • Bring your inhalers

    List every device and dose. The physiologist needs to know exactly what you have taken and when.

Indicative pricing

Honest ranges across UK units.

Test Indicative range
Spirometry alone (FEV1, FVC, FEV1/FVC, flow-volume loop) £180-£320
Spirometry with reversibility (pre and post bronchodilator) £220-£380
Full PFT: spirometry + lung volumes (body plethysmography) + DLCO £350-£650
FeNO (eosinophilic airway inflammation) add-on £80-£150
MIP / MEP / SNIP (respiratory muscle strength) £120-£240
MBW (multiple breath washout) or FOT (forced oscillation) £200-£400
Full PFT bundle with consultant respiratory physician consultation £450-£850

Related

The wider chest workup.

What often sits alongside lung function testing.

  • Bronchoscopy

    Direct airway visualisation with sampling for infection, inflammation or malignancy.

    Read more

  • Private CT scan

    HRCT chest for ILD, emphysema and nodule characterisation.

    Read more

  • CPEX / CPET

    Cardiopulmonary exercise testing. Covered on a separate page.

    Read more

  • Asthma biologics clinic

    Anti-IgE, anti-IL5 and anti-TSLP therapy for severe eosinophilic asthma.

    Read more

  • Bronchial thermoplasty

    For severe persistent asthma resistant to standard therapy.

    Read more

  • Asthma

    Diagnosis, monitoring and modern step-up therapy.

    Read more

  • COPD

    Fixed obstruction: diagnosis, phenotyping and treatment.

    Read more

  • Interstitial lung disease

    ILD diagnosis, DLCO monitoring and antifibrotic therapy.

    Read more

Frequently asked

What people ask before enquiring.

  • Do I need a referral for spirometry or full PFT?

    Spirometry and reversibility usually accept self-referral. Full PFT with lung volumes and DLCO is normally requested by a respiratory physician.

  • How is spirometry different from a full PFT?

    Spirometry measures FEV1, FVC and the FEV1/FVC ratio using a mouthpiece and a spirometer. A full PFT adds body plethysmography for true lung volumes (TLC, RV, FRC) and DLCO for gas transfer, plus optional respiratory muscle testing. Spirometry cannot diagnose restriction on its own.

  • Should I take my inhalers before the test?

    For reversibility testing, your team may ask you to withhold SABA for 4 hours, LABA for 12 hours and LAMA for 24 hours where safe. Never stop rescue medication without clinical advice. Bring every inhaler you use to the appointment.

  • How accurate are the results?

    Very accurate when performed to ATS/ERS 2019 standards on calibrated equipment with a trained physiologist and reproducible efforts (minimum three acceptable manoeuvres). Reports use GLI reference equations with the lower limit of normal (LLN) and z-scores rather than a fixed percent predicted.

  • Will my insurance cover it?

    Most policies cover lung function testing when medically indicated and pre-authorised.

  • Can I have FeNO on the same visit?

    Yes. FeNO takes about ten minutes and is usually done first, before spirometry, to avoid manoeuvres influencing the reading. It is particularly useful when eosinophilic asthma is suspected.