Respiratory Causes of Breathlessness – London & Surrey

Respiratory causes of shortness of breath include asthma, chronic obstructive pulmonary disease (COPD), chest infections and conditions affecting the lung tissue, lining or blood vessels. The pattern of your symptoms helps guide assessment, but symptoms alone rarely establish the diagnosis.

You may notice breathlessness when walking or climbing stairs, or find that you can no longer maintain your usual running pace. A new or worsening change deserves attention, even if you have never smoked or your first tests were normal.

This article explains the main lung and airway causes of breathlessness, the investigations that may help and when to seek urgent care. More than one cause may be present.

When shortness of breath needs urgent help

Call 999 if you have:

• Sudden unexplained breathing difficulty, or severe breathlessness with gasping, choking or being unable to get words out.
• A tight or heavy chest, or pain spreading to your arms, back, neck or jaw.
• Sudden confusion, or skin or lips becoming blue, grey or very pale.
• Heart palpitations happening now with shortness of breath, chest pain, feeling faint or fainting.
• Coughing up more than a few spots or streaks of blood, or coughing up blood with breathing difficulty, a very fast heartbeat, or chest or upper back pain.

Do not drive yourself to A&E.

Contact NHS 111 urgently for new or increased breathing difficulty without the emergency features above, pain or swelling in one leg, or a few small spots or streaks of blood in your phlegm. If palpitations with breathlessness, chest pain or faintness have now stopped, ask for an urgent GP appointment or contact NHS 111.

Follow the NHS advice on shortness of breath. Do not wait for a routine appointment if you are acutely unwell.

What breathlessness can feel like

Shortness of breath, also called breathlessness or dyspnoea, is the uncomfortable feeling that breathing requires more effort or is not satisfying. It may feel like chest tightness, air hunger or difficulty taking a full breath.

The timing matters. Symptoms appearing suddenly require a different assessment from breathlessness developing over months. Your doctor will also ask whether symptoms occur at rest, during exercise, at night or when lying flat, and whether you have cough, wheeze, fever or chest pain.

Common respiratory causes of breathlessness

Asthma

Asthma causes inflammation and variable narrowing of the airways. Breathlessness may come with wheezing, cough or chest tightness, and symptoms often vary between days. Night-time symptoms, cold air, exercise, pollen, pets and viral infections can provide useful clues.

Asthma can start in adulthood. Repeated episodes labelled as chest infections may warrant assessment for an underlying airway condition, particularly when there is wheezing or a cough that keeps returning.

Diagnosis should combine a compatible history with objective evidence. Tests may include a blood eosinophil count, a fractional exhaled nitric oxide (FeNO) test, spirometry with bronchodilator reversibility, or a peak-flow diary. Further testing may be needed if initial results are inconclusive. The BTS, NICE and SIGN asthma guideline sets out this approach.

COPD and emphysema

COPD causes persistent airflow obstruction. Breathlessness often becomes gradually more noticeable during activity, sometimes alongside a longstanding cough, regular sputum and repeated chest infections. Emphysema is damage to the air sacs that can form part of COPD.

Smoking is the main risk factor, but occupational dust, fumes and other exposures also matter. A smoking history alone does not establish the diagnosis: post-bronchodilator spirometry is needed to confirm persistent airflow obstruction in the appropriate clinical context.

Unusually early disease, little or no smoking history, or a relevant family history may prompt testing for alpha-1 antitrypsin deficiency, an inherited condition that can affect the lungs and liver.

Chest infections and pneumonia

Pneumonia can cause breathlessness over hours or days, usually with cough and sometimes fever, sputum or pain when breathing. Older adults may have less obvious symptoms, including confusion or marked weakness.

Breathing that worsens or fails to improve as expected needs reassessment. After hospital treatment for pneumonia, a follow-up chest X-ray is not automatically needed for everyone. NICE recommends considering an X-ray at about six weeks after discharge when symptoms persist or deteriorate, there is unexplained weight loss, or there are risk factors for underlying respiratory disease or lung cancer, such as smoking or age over 50.

Bronchiectasis

Bronchiectasis is permanent widening and damage of the airways, which can allow mucus to collect and infections to recur. A persistent productive cough, sputum on most days and frequent courses of antibiotics are common clues. Some people cough up blood.

A chest CT scan is usually needed to confirm the diagnosis. Treatment may include airway-clearance physiotherapy, treatment of infections and investigation of any underlying cause. New coughing up of blood needs prompt medical advice, with emergency help for the features described above.

Interstitial lung disease and pulmonary fibrosis

Interstitial lung diseases affect the tissue around the lung’s air sacs. Some cause scarring, known as pulmonary fibrosis, which makes the lungs stiffer and can impair oxygen transfer.

Typical features include gradually increasing breathlessness on exertion and a persistent dry cough. A clinician may hear fine crackles when listening to the lungs. Oxygen levels can fall during walking even when resting readings are normal.

Assessment may require full lung-function testing, including gas transfer, and a high-resolution CT scan. Specialist review helps distinguish the different conditions, which have different treatments. Some fibrotic lung diseases can be treated with medicines that slow progression in suitable patients.

Pulmonary embolism

A pulmonary embolism is a blood clot blocking a blood vessel in the lungs. It belongs in the assessment of respiratory symptoms even though it affects the circulation.

Symptoms can include sudden unexplained breathlessness, pain on breathing, a rapid heartbeat, coughing up blood or collapse. Risk factors include recent surgery, immobility, previous clots, cancer, pregnancy and oestrogen-containing medicines, although a clot can occur without an obvious trigger.

Suspected pulmonary embolism needs urgent assessment. NHS guidance on pulmonary embolism advises emergency help for sudden breathing difficulty, chest or upper back pain, a very fast heartbeat or collapse. Call 999 and do not drive yourself to A&E.

A normal chest X-ray does not rule out a pulmonary embolism. Assessment may involve a clinical risk score, a D-dimer blood test and an appropriate scan. The choice and order of tests depend on how likely a clot is.

In some people, blood clots do not fully resolve and leave persistent obstruction or scarring in the lung arteries. This can cause chronic thromboembolic pulmonary hypertension, or CTEPH, where raised pressure in these blood vessels contributes to ongoing breathlessness.

Pleural effusion and pneumothorax

A pleural effusion is fluid collecting between the lung and chest wall. It can restrict lung expansion and may result from infection, heart failure, cancer or another condition. Finding the underlying cause is essential.

A pneumothorax occurs when air enters this space, allowing part or all of the lung to collapse. Sudden breathlessness with sharp, often one-sided chest pain requires emergency assessment. Imaging helps identify the problem; treatment depends on its severity and cause.

Lung cancer

Breathlessness has many non-cancerous causes, but persistent unexplained symptoms need assessment. A continuing cough, coughing up blood, unexplained weight loss, appetite loss or repeated chest infections should be mentioned to your doctor. Lung cancer can occur in people who have never smoked.

NICE guidance on suspected lung cancer recommends an urgent chest X-ray for people aged 40 or over with two or more unexplained symptoms from cough, fatigue, breathlessness, chest pain, weight loss or appetite loss. For someone aged 40 or over who has ever smoked, one of these unexplained symptoms meets that criterion.

Unexplained coughing up of blood at age 40 or over meets the criterion for a suspected cancer pathway referral. These criteria guide clinicians; they are not a reason for younger people to ignore concerning symptoms.

A normal X-ray does not completely exclude lung cancer, so persistent or changing symptoms still need review.

Other breathing problems that may need assessment

Sleep apnoea and breathing during sleep

Obstructive sleep apnoea causes repeated narrowing or closure of the upper airway during sleep. Loud snoring, witnessed pauses, waking with choking or gasping, morning headaches and daytime sleepiness are useful clues.

It should not automatically be used to explain daytime breathlessness on exertion, which may have another cause. A sleep study, often performed at home, can investigate suspected sleep apnoea. Smartwatch readings alone cannot establish the diagnosis.

Breathlessness during running or cycling

Exercise-induced bronchoconstriction can cause cough, wheeze or chest tightness during or after exercise. Another possibility is inducible laryngeal obstruction, where the voice box temporarily narrows, often causing throat tightness, noisy breathing or difficulty breathing in.

These conditions can coexist and need different approaches. Tests performed at rest may not reproduce symptoms, so selected patients need exercise-related breathing tests or assessment of the larynx.

For people exercising in London, traffic pollution may aggravate airway symptoms. Tell your clinician if particular routes or exposures trigger symptoms, but do not assume pollution explains a persistent drop in exercise capacity.

Long COVID and post-viral breathlessness

Persistent breathlessness after a viral illness can reflect airway inflammation, changes in lung function, breathing pattern disorder, reduced fitness or problems outside the lungs. Long COVID can involve several systems at once.

The assessment should look for treatable contributors and new conditions, rather than assuming every symptom has the same cause. If activity causes a delayed worsening of fatigue or other symptoms, tell your clinician before increasing exercise.

How respiratory causes of breathlessness are investigated

Assessment starts with your history and examination, including pulse, breathing rate and oxygen saturation. It should also consider the heart and other possible causes. Depending on the findings, investigations may include:

Investigation	What it can help assess
Spirometry and bronchodilator testing	Airflow obstruction and changes after an inhaled medicine.
FeNO and selected blood tests	Evidence supporting asthma and possible non-lung contributors.
Chest X-ray	Pneumonia, pleural problems and some other chest abnormalities.
Full lung-function tests	Lung volumes and gas transfer between the lungs and blood.
Walking oxygen assessment	Whether oxygen saturation falls during exertion.
Selected CT or exercise testing	A suspected condition or symptoms unexplained by initial tests.

Not everyone needs every investigation. Tests such as CT pulmonary angiography, sleep studies or cardiopulmonary exercise testing answer specific clinical questions. Bronchoscopy is reserved for situations where inspecting or sampling the airways is appropriate.

Our guide to tests for unexplained breathlessness explains the main investigations and what happens when initial results do not explain your symptoms.

Bring previous results, a current medication list and details of smoking or workplace exposures. A concrete comparison is helpful: “I used to climb three flights of stairs; now I stop after one.”

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