Tests for Unexplained Breathlessness in London and Surrey

Tests for unexplained breathlessness often start with blood tests, an ECG, a chest X-ray and spirometry. Depending on the findings, further investigations may include detailed lung function tests, an echocardiogram or chest CT. Cardiopulmonary exercise testing (CPET) can help when symptoms remain unexplained, particularly during activity. You will not necessarily need every test.

This guide explains the main investigations for adults and how to arrange a respiratory assessment in London, Kingston upon Thames or Ashtead.

When breathlessness needs urgent help

Call 999 for severe breathing difficulty, inability to speak because of breathlessness, a tight or heavy chest, pain spreading to the arms, back, neck or jaw, very pale, blue or grey skin or lips, or sudden confusion. Do not drive yourself to A&E.

Call 999 if you cough up more than a few spots of blood, or cough up blood alongside breathing difficulty, a very fast heartbeat, or chest or upper-back pain.

Contact NHS 111 urgently for increased breathlessness, pain or swelling in one leg, or small blood streaks without the emergency features above.

What does unexplained breathlessness mean?

Breathlessness is described as unexplained when the assessment so far has not adequately accounted for your symptoms. More than one condition may contribute.

NHS England’s chronic breathlessness pathway covers persistent symptoms lasting more than eight weeks. This is not a reason to wait eight weeks before seeking help: new, worsening or activity-limiting symptoms need assessment sooner.

For background on possible causes, see the practice’s breathlessness information.

What happens before testing?

Your clinician will ask when symptoms started, what makes them better or worse, how they affect everyday tasks and which medicines you take. A physical examination helps guide testing.

Bring previous test reports and a current medicine list. Note which activities bring on symptoms and how long recovery takes. This helps the clinician decide which results need reviewing and which investigations may add useful information.

Which tests are usually considered first?

Oxygen measurements and walking tests

A pulse oximeter estimates blood oxygen saturation using a finger sensor. A normal reading does not explain breathlessness or exclude a breathing problem. Movement, poor circulation and skin pigmentation can affect accuracy; readings may overestimate oxygen levels in people with darker skin. Results need interpreting alongside symptoms.

If appropriate, a supervised walking assessment checks what happens during activity. A six-minute walk test records walking distance and can monitor oxygen levels and symptoms. It assesses your response to exertion but does not establish the cause by itself.

Blood tests

A full blood count checks for anaemia. Depending on your symptoms, other blood tests may assess thyroid function or diabetes.

NT-proBNP helps assess suspected heart failure. NICE recommends specialist assessment and echocardiography within six weeks for levels of 400 to 2,000 ng/L, or within two weeks for levels above 2,000 ng/L. A result below 400 ng/L in an untreated person makes heart failure less likely but does not exclude it in every case. Obesity, medicines and other illnesses can affect the result. These referral intervals concern suspected chronic heart failure, not emergency symptoms.

D-dimer is not a routine breathlessness blood test. It is used within a clinical pathway for suspected blood clots. A positive result does not diagnose a clot; when pulmonary embolism is likely, urgent imaging may be needed without waiting for D-dimer.

ECG

An electrocardiogram records the heart’s electrical activity and can identify rhythm abnormalities. If symptoms are intermittent, a portable monitor may be useful because a short resting ECG may not capture an episode.

Chest X-ray

A chest X-ray can show changes such as infection or fluid, but it cannot exclude every lung condition. Even lung cancer does not always appear on an X-ray. Persistent symptoms may require further assessment despite a normal result. This does not mean everyone needs a CT scan.

Spirometry and asthma tests

Spirometry measures the volume and speed of air you breathe out. It helps identify airflow obstruction, including patterns seen in asthma and chronic obstructive pulmonary disease (COPD). It can suggest reduced lung volumes, but spirometry alone cannot confirm restriction; that requires measurement of total lung capacity.

If asthma is suspected, testing may include blood eosinophils, fractional exhaled nitric oxide (FeNO), bronchodilator reversibility or peak-flow monitoring. FeNO measures a marker of airway inflammation. In people over 16 with a history suggesting asthma, the BTS/NICE/SIGN guideline uses FeNO of 50 parts per billion or more as one diagnostic criterion. A normal result does not exclude asthma, particularly after treatment with inhaled corticosteroids.

What if the first tests do not explain the symptoms?

Full lung function tests and gas transfer

Full lung function testing may add lung volumes and gas transfer to spirometry. Lung volumes can be measured in a transparent booth or by other techniques. Gas transfer, also called TLCO or DLCO, assesses transfer from the lungs into the blood using a small amount of carbon monoxide in a test gas mixture. It is not a direct measurement of oxygen transfer.

A low gas transfer result can occur with emphysema, interstitial lung disease or pulmonary vascular disease. Anaemia and test quality also affect interpretation. The finding is a clue, not a diagnosis, and can occur alongside normal spirometry.

Echocardiogram

An echocardiogram uses ultrasound to assess the heart’s structure, valves and function. A normal ejection fraction, which describes the proportion of blood pumped out with each beat, does not by itself exclude heart failure. Some patients need further assessment for heart failure with preserved ejection fraction.

Echocardiography can also suggest pulmonary hypertension, but confirmation may require right heart catheterisation at a specialist centre.

CT scans and investigations for blood clots

The type of scan depends on the clinical question:

• High-resolution chest CT helps assess suspected interstitial lung disease. Diagnosis may require specialist review alongside other findings.
• CT pulmonary angiography (CTPA) uses contrast to investigate suspected pulmonary embolism. A ventilation/perfusion scan, often called a V/Q scan, is an alternative in selected circumstances.
• V/Q scanning also has an established role in investigating suspected chronic thromboembolic pulmonary hypertension, where longstanding clots affect blood flow through the lungs. It is not reserved only for inconclusive CT scans.

Bronchial challenge testing

If asthma remains suspected after initial tests, a specialist may recommend a bronchial challenge test to assess whether the airways narrow excessively. The choice depends on your symptoms and earlier results.

Sleep studies

Loud snoring, witnessed pauses in breathing and unrefreshing sleep may prompt assessment for obstructive sleep apnoea. Questionnaires can support assessment but cannot diagnose it alone. NICE generally recommends home respiratory polygraphy, which monitors breathing during sleep; overnight oximetry may be considered when access is limited. Persistent symptoms can warrant further testing after a negative result.

When is cardiopulmonary exercise testing useful?

CPET assesses how your body responds to increasing exercise, usually on a stationary bicycle. You wear a mask or mouthpiece to measure oxygen uptake and carbon dioxide output while staff monitor your heart rhythm, oxygen saturation and blood pressure.

The results can help identify patterns of heart or lung limitation, reduced fitness or abnormal breathing during exertion. They may guide treatment or indicate which further investigation is needed. CPET does not guarantee a diagnosis or identify every underlying condition on its own.

Routine CPET is different from invasive CPET, which adds measurements through catheters in blood vessels.

Other reasons for breathlessness with normal initial tests

Breathing pattern disorder

Altered breathing patterns can cause breathlessness, frequent sighing or difficulty getting a satisfying breath. Assessment may include observation by a respiratory physiotherapist. A questionnaire such as the Nijmegen Questionnaire can help screen symptoms, but it cannot establish the diagnosis alone. Breathing retraining may help, while coexisting conditions still need appropriate treatment.

Breathlessness during sport

Exercise-related symptoms may require testing for exercise-induced airway narrowing or inducible laryngeal obstruction, where the voice box narrows during breathing. For suspected exercise-induced laryngeal obstruction, clinicians may examine the larynx with a small camera during exercise. It can resemble asthma, and the two conditions can coexist.

Breathlessness after COVID-19

Persistent symptoms after COVID-19 need assessment even when initial tests are normal. Rehabilitation should be individualised. If activity causes delayed worsening of symptoms, known as post-exertional symptom exacerbation, tell your clinician before exercise testing or rehabilitation. WHO guidance supports pacing your activities for this problem and assessment of cardiac impairment and exercise-related oxygen drops before exercise training.

Frequently asked questions (FAQs) about unexplained breathlessness

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This article provides general information and does not replace an individual medical assessment.