• Silent myocardial infarction
• Risk factors — smoking, high blood lipid levels, hypertension, obesity, diabetes, family history.
• Symptoms — breathlessness, general malaise, sudden collapse, upper body discomfort.
• Signs — breathless (sometimes), abnormal pulse rate, sweating, reduced peripheral perfusion.
• Electrocardiogram (ECG) — features suggestive of acute MI include ST depression with T-wave inversion, persistent ST elevation, or new left bundle branch block. Q-waves are characteristic of a resolved MI.
• Cardiac arrhythmia
• Risk factors — heart failure, valvular heart disease, ischaemic heart disease.
• Symptoms — palpitations, breathlessness, chest pain, syncope (or near syncope).
• Signs — bradycardia or tachycardia.
• ECG — changes that are evident when the person is symptomatic are diagnostic. Typical ECG features of supraventricular tachycardia (SVT) that are treatable in primary care include:
• P-waves (usually not identifiable), regular narrow QRS complex tachycardia (unless the person has a bundle branch block as well), and a rate that is usually 130–250 bpm.
• For an image of a typical SVT trace, see Wikimedia Commons.
• Acute pulmonary oedema
• Risk factors — chronic heart failure, ischaemic heart disease, valvular heart disease.
• Symptoms — severe breathlessness, orthopnea, coughing (rarely frothy blood-stained sputum).
• Signs — elevated jugular venous pressure, gallop rhythm, inspiratory crackles at lung bases, and (occasionally) wheeze. Peripheral circulation is shut down (in contrast to people with an acute exacerbation of chronic obstructive pulmonary disease).
• Chronic heart failure
• Risk factors — hypertension, ischaemic heart disease, valvular heart disease, chronic cardiac arrhythmia.
• Symptoms — fatigue and breathlessness, including orthopnea and paroxysmal nocturnal dyspnoea.
• Signs — basal crackles, displaced apex beat, third heart sound, and (if congestive cardiac failure is present) increased jugular venous pressure, dependent oedema, and hepatomegaly.

Clinical features of silent myocardial infarction

• These are based on evidence, from observational studies, that is summarized in an expert review of the clinical features of people with confirmed myocardial infarction presenting without chest pain [Wong and White, 2002].

Clinical features of cardiac arrhythmia

• These are based on expert observation reported in the Oxford textbook of medicine [Cobbe et al, 2010].
• The ECG features of SVT are based on expert observation reported in The ECG in practice [Hampton, 2008].

Clinical features of pulmonary oedema

• These are based on expert observation reported in the Oxford textbook of medicine [Morrell and Firth, 2010].

Clinical features of chronic heart failure

• These are based on expert observation reported in guidelines issued by National Collaborating Centre for Chronic Conditions, the Scottish Intercollegiate Guidelines Network, and the European Society of Cardiology [National Collaborating Centre for Chronic Conditions, 2003; SIGN, 2007; European Society of Cardiology, 2008].

• Asthma
• Risk factors — personal history of rhinitis or eczema, or family history of atopy.
• Symptoms — wheeze, breathlessness, cough. Symptoms are variable (often worse at night, first thing in the morning, and upon exercise or exposure to cold or allergens).
• Signs — there may be none when the person is feeling well. During an acute episode, the respiratory rate is increased, and wheeze is usually present.
• Peak expiratory flow rate (PEFR) is reduced during an acute episode. Acute asthma is:
• Life-threatening — when PEFR is less than 33% of predicted, and is associated with tachycardia, hypotension, a silent chest, or impaired level of consciousness.
• Severe — when PEFR is 33–50% of predicted, and is associated with a respiratory rate of more than 25 breaths per minute and an inability to complete full sentences.
• Moderate — when PEFR is more than 50% of predicted, with a respiratory rate of less than 25 breaths per minute.
• Chronic obstructive pulmonary disease
• History — typically, the person is older than 35 years of age, is a smoker (or past smoker), and reports slowly progressive breathlessness.
• Symptoms — persistent progressive breathlessness that is often associated with wheezing or chest tightness, and a cough (producing purulent sputum). Acute exacerbations of symptoms are common, and are frequently caused by respiratory tract infection.
• Signs — wheeze, hyperinflated chest (in emphysema), crackles (when infection is present). There may be signs of right-side heart failure in people with severe disease, including swollen ankles and increased jugular venous pressure. The person's peripheries (the hands and feet) are often warm to the touch and a dusky colour (cyanosed), with distended veins.
• Pneumonia
• Symptoms — cough associated with at least one other symptom of breathlessness, sputum production, wheeze, or pleuritic pain.
• Signs — any focal chest sign (such as dull percussion note, bronchial breathing, coarse crackles, or increased vocal fremitus/resonance) plus at least one systemic feature (such as fever/sweating, myalgia), with or without a temperature greater than 38°C. There may be signs of an associated pleural effusion.
• Pulmonary embolism (PE)
• Risk factors — immobilization, surgery, cancer, symptoms or signs of deep vein thrombosis (DVT).
• Symptoms — acute-onset breathlessness (in 73% of people with PE), pleuritic pain (66%), cough (37%), haemoptysis (13%). Recurrent acute episodes may lead to chronic breathlessness.
• Signs — tachypnoea of more than 20 breaths per minute (in 70% of people with PE), crackles (51%), tachycardia (30%), signs of DVT (11%).
• Pneumothorax/tension pneumothorax
• Risk factors — smoking, age and body type (adults who are young, tall, and slim), previous pneumothorax, chronic respiratory disease (such as chronic obstructive pulmonary disease or asthma), trauma to chest wall (including therapeutic procedures such as injections and aspirations).
• Symptoms — collapse, sudden-onset pleuritic pain, breathlessness.
• Signs — reduced chest wall movements, reduced breath sounds, reduced vocal fremitus, and increased resonance of the percussion note on the affected side. Tension pneumothorax can result in a rapid development of severe symptoms associated with tracheal deviation away from the pneumothorax, tachycardia, and hypotension.
• Pleural effusion
• Causes — include: heart, liver, or renal failure; pneumonia; pulmonary embolism; cancer (including mesothelioma); tuberculosis; pleural infection (empyema); and autoimmune disease.
• Symptoms — progressive breathlessness.
• Signs — reduced chest wall movements on the affected side, stony dull percussion note, diminished or absent breath sounds, and (in people with heart or renal failure) signs of fluid overload.
• Lung/lobar collapse
• Causes — airway compression (for example by enlarged lymph nodes infiltrated with cancer) or blockage (secondary to pneumonia or an inhaled foreign body).
• Symptoms — breathlessness, cough.
• Signs — reduced chest wall movement on the affected side, dull percussion note with bronchial breathing, reduced or diminished breath sounds.
• Bronchiectasis
• History — suspect in people with a history of recurrent or chronic productive cough, especially if they do not smoke.
• Symptoms — cough with daily sputum production (present in 75–100% of adults), progressive breathlessness (72–83%), haemoptysis (51–45%), non-pleuritic chest pain between exacerbations (31%).
• Signs — coarse crackles during early inspiration that are heard in the affected areas, usually in the lower lung fields (70% of adults). Others include wheeze (34%) and large airway rhonci (44%). Finger clubbing occurs infrequently.
• Interstitial lung disease (ILD)
• Causes — include idiopathic pulmonary fibrosis, sarcoidosis, pneumoconioses, ILD associated with drug therapy, ILD associated with connective tissue disease, and hypersensitivity pneumonitis/extrinsic allergic alveolitis (following sensitization to inhaled environmental allergens; for example from birds, hay, or mushrooms).
• Symptoms — cough and slowly progressive breathlessness. When it is caused by extrinsic allergic alveolitis there may be a history of recurrent episodes of flu-like illness following exposure to the responsible allergen. There may be symptoms of the underlying cause (for example joint pains when the ILD is associated with connective tissue disease).
• Signs — there may be none in sarcoidosis. When present, there may be fine end-inspiratory crepitations (indicative of fibrosis), finger clubbing, cyanosis, and signs of right heart failure.

Clinical features of pulmonary embolism

• These are based on evidence from a diagnostic study of the clinical features associated with confirmed pulmonary embolism [Stein et al, 1991].

Clinical features of pneumothorax

• These are based on expert observation reported in the Oxford textbook of medicine [Davies et al, 2010].

Clinical features of tension pneumothorax

• These are based on expert observation reported in the Oxford handbook of general practice [Simon et al, 2010].

Clinical features of asthma

• These are based on expert observation, supported by observational studies reported in the British guideline on the management of asthma, issued by the British Thoracic Society and Scottish Intercollegiate Guidelines Network [SIGN and BTS, 2009].

Clinical features of chronic obstructive pulmonary disease

• These are based on expert observation reported in the guideline Chronic obstructive pulmonary disease: national clinical guideline on management of chronic obstructive pulmonary disease in adults in primary and secondary care [National Clinical Guideline Centre, 2010].

Clinical features of bronchiectasis

• These are based on a summary of the evidence from observational studies, reported in the British thoracic society guideline for non-CF bronchiectasis [British Thoracic Society, 2010].

Diagnostic criteria for clinical features of community-acquired pneumonia

• These are based on an assessment of the evidence on the sensitivity of clinical features to diagnose pneumonia, summarized in the British Thoracic Society guidelines on The management of community acquired pneumonia [British Thoracic Society, 2001; British Thoracic Society, 2009].

Clinical features of interstitial lung disease

• These are based on expert observation reported in the Oxford textbook of medicine [Wells and Hirani, 2008; Baughman and Lower, 2010; Hendrick and Spickett, 2010; Seaton, 2010].

Clinical features of lung/lobar collapse

• These are based on expert observation reported in the textbook Clinical medicine [Frew and Holgate, 2005].

Clinical features of pleural effusion

• These are based on expert observation reported in the Oxford textbook of medicine [Davies et al, 2010].

• Anaemia
• Symptoms — fainting, exertional breathlessness, fatigue, palpitations.
• Signs — paleness (for example of the conjunctiva or palms).
• Diaphragmatic splinting (due to ascites, obesity, or pregnancy)
• Symptoms — chronic breathlessness that develops in association with increasing abdominal size. There are no symptoms to suggest other causes of chronic breathlessness.
• Signs — ascites (shifting dullness and fluid thrill) or obesity. There are no clinical features of other causes for chronic breathlessness.
• Psychogenic breathlessness
• History — the person has no identifiable risk factors for a physical cause of breathlessness. Anxiety disorders are common, especially panic disorders. The episode is often preceded by a stressful event.
• Symptoms — breathlessness is characteristically intense and may be associated with symptoms of hyperventilation (including tingling of the extremities, tetanus, and light-headiness). Other symptoms, such as palpitations and chest pain, may occur. Symptoms of anxiety may accompany breathlessness.
• Signs — no signs of a physical cause for breathlessness. Breathing pattern may be irregular and gasping, and accompanied by sighing.

Clinical features of anaemia

• These are based on expert observation reported in the Oxford textbook of medicine [Weatherall, 2010].

Clinical features of the causes of abdominal splinting

• These are based on expert observation reported in Macleod's clinical examination [Ford et al, 2009].

Clinical features of psychogenic breathlessness

• These are based on observational data from a Chinese study of 111 people with psychogenic breathlessness [Han et al, 2004].