Wheezing: Causes Other Than Asthma

Sounds from the airways are classified by the site of narrowing. A wheeze arises in the bronchi inside the chest and is best heard on breathing out, because that is when they narrow most. Stridor is a loud, often harsh sound usually heard on breathing in, pointing to narrowing in the upper airway: the throat, larynx or upper trachea. The difference is practical: wheeze points thoughts towards diseases of the bronchi and heart, stridor towards problems of the larynx, trachea or a foreign body.

In practice the boundary can be blurred: with severe upper airway obstruction the sound may be heard on both breathing in and out, and bystanders often call everything 'wheezing'. It helps to ask whether the sound is louder on breathing in (more stridor) or out (more wheeze), whether it is loudest at the neck (upper airway) or over the lungs, and whether it changes after bronchodilator medicines. No improvement after an inhaler is one clue towards upper airway obstruction.

Many people have not one but several diseases that cause wheezing and breathlessness. Asthma, COPD and heart failure overlap particularly often, and telling them apart is harder than it seems. We write about emphysema and COPD in an entry in the knowledge base, and about NT-proBNP in a separate entry on cardiac markers.

Practical conclusion: wheezing in an older person, a smoker or someone with heart disease should not be automatically attributed to asthma. The same symptom can result from congestion in the lungs in heart failure (colloquially 'cardiac asthma'), and then an inhaled bronchodilator brings only partial relief, whereas treating the heart is the key. Conversely, a person with COPD may have heart failure at the same time, which is easy to overlook. NT-proBNP, an ECG and an echocardiogram help (we write about a normal NT-proBNP in early heart failure in our article on exertional breathlessness), as does spirometry.

Vocal cord dysfunction, today more often called inducible laryngeal obstruction (ILO), means that the vocal cords or structures above them wrongly narrow the entrance to the airway on breathing in. Attacks come on suddenly, often in response to exercise, smells, smoke, chemicals, laughter, cough and sometimes stress. The person feels tightness in the throat, difficulty breathing in and an audible stridor, and the classic asthma drugs do not help. It is often mistaken for asthma and so is described as a common mimic of it, but it can also coexist with asthma and reflux.

What follows? First, ILO is a real and common mimic of both asthma and anaphylaxis, but it has to be diagnosed by examination (laryngoscopy, with spirometry as support), not from a description alone. Second, clinical features help: predominant throat and larynx symptoms (tightness, voice change, stridor), absence of hives and systemic symptoms, and many different triggers favour ILO. Third, one must not conclude that every wheeze with throat tightness is ILO: anaphylaxis is life-threatening, so with sudden breathlessness after food, a drug or a sting, especially with swelling, hives or dizziness, help is always called (112), and differentiation is left to specialists.

The basis of treatment of ILO is not inhaled drugs but speech pathology (breathing therapy): the person learns to recognise the start of an attack and to control breathing so as to relax the throat and larynx. Until recently data from randomised trials were sparse, but new studies are appearing.

Several things follow for the reader. Speech pathology is the basis of treatment of ILO and most treated people feel improvement (74% in one trial, about 63-64% in the other), although neither trial had a no-intervention group, so we do not know how much of the improvement is due to the therapy itself. Adding a drug (amitriptyline) gave no extra benefit, and biofeedback did not differ from classic respiratory retraining. The availability of specialists (speech therapists working on breathing, ENT specialists with laryngoscopy) depends on the region and we will not assess it for Poland here.

The basic test for wheezing is spirometry, which we describe in an entry in the knowledge base. It measures how fast and how much air can be blown out, and detects airway obstruction and assesses its reversibility after a bronchodilator. Spirometry also records the so-called flow-volume loop, a graph in which both breathing out and breathing in have a characteristic shape. Changes of that shape (flattening of the inspiratory or expiratory part) may indicate narrowing of the upper airway, which distinguishes it from ordinary bronchial obstruction.

Conclusion: the flow-volume loop is a cheap addition to spirometry that can suggest the problem lies in the upper airway, but it does not settle the diagnosis on its own. When upper airway obstruction or ILO is suspected, laryngoscopy (looking at the larynx with a thin endoscope) is usually needed, and when structural changes are in doubt, CT or bronchoscopy. When symptoms suggest the heart, NT-proBNP and an echocardiogram are added. When they suggest reflux, assessment of the oesophagus is considered (see the entry on reflux).

Equally mistaken is the belief that wheezing without obvious disease is 'just nerves'. Attacks of breathlessness with throat tightness are sometimes dismissed as anxiety, yet they have a physical explanation that can be examined and treated. It is worth going back to the doctor and asking for a wider work-up.

Wheezing is a symptom that too often ends up with a single label. The data show that several diseases can lie behind wheezing at once, and each needs different treatment: bronchi, heart, upper airway, allergy or reflux. A sensible order is a precise description of symptoms (when, on breathing in or out, what triggers it, whether a drug helps), spirometry with a flow-volume loop, tests of the heart and laryngoscopy if needed, and in the background a clear list of situations in which one does not wait at all. It is especially worth remembering that lack of improvement on asthma treatment is not the patient's failure but a diagnostic clue.