38 CLINICAL FOCUS
38 CLINICAL FOCUS
20 MARCH 2026 ausdoc. com. au
Therapy Update NEED TO KNOW
A hidden cause of dyspnoea
DYSPNOEA is a very common symptom globally, and in Australia it affects around 30 % of the population. 1, 2 It remains one of the most frequent complaints encountered in both primary care and EDs, contributing substantially to unplanned healthcare utilisation. 2, 3
Despite its prevalence, a significant proportion of individuals with this symptom do not have a definitive respiratory or cardiac diagnosis. 4 Data from national surveys suggest that many individuals with limiting dyspnoea remain undiagnosed or misdiagnosed. 3 Among those who are diagnosed with a respiratory condition such as asthma, symptom control is often suboptimal despite the availability of effective treatment strategies. 5
The differential diagnosis of breathlessness is broad, encompassing respiratory, cardiac, neuromuscular and psychological causes. In clinical practice, however, paroxysmal breathlessness in individuals without established cardiopulmonary disease is frequently attributed to asthma— often without adequate diagnostic confirmation. Approximately one in nine Australians is treated for asthma, reflecting a substantial cumulative impact on individuals and the healthcare system. 6 Objective testing, such as peak expiratory flow measurements and spirometry, is under-utilised in primary care settings. When
Table 1. Questions to help differentiate asthma from inducible
23, 26 laryngeal obstruction Inducible laryngeal obstruction
Very rapid onset- Symptoms are‘ instant’ or within seconds
Strong odours- Perfumes, cleaning products
Particulate matter- Bushfire or wood smoke, secondhand smoke, pollution
Mechanical factors- Talking, laughing
Psychological factors
- Stress Exercise
No- Patients will describe taking multiple puffs of their reliever with very little effect, or- Instant effect, within seconds, out of keeping with true medication effect onset
‘ How quickly does it come on?’
Asthma
Gradual onset- Symptoms build over 15-30 minutes
‘ What can trigger it?’
Allergens- Hay fever, mould, animal dander, dust, some foods
Particulate matter- Bushfire or wood smoke, second-hand smoke- Gas appliances Change in weather Viral infections Psychological factors
- Stress Exercise
‘ Does it respond to bronchodilators?’
Yes- Uses correct dose of bronchodilators- Relief within 5-10 minutes
‘ What symptoms do you get during an attack?’
- More difficulty breathing in- Stridor( inspiratory)- Throat tightness / constriction- Cough / throat clearing— occurs throughout the day, does not cause nocturnal waking- Voice changes
Respiratory
Dr Alice Crawford( top left) is a respiratory physician at Sir Charles Gairdner Hospital and adjunct clinical lecturer at Curtin Medical School and the School of Allied Health, Curtin University, Perth, WA. Zoe Castillo( top right) is a research administration officer at the Institute for Respiratory Health, Perth, WA. Kate Baumwol( bottom left) is a speech pathologist at Sir Charles Gairdner Hospital, Perth, WA.
Professor John Blakey( bottom right) is a respiratory physician at Sir Charles Gairdner Hospital, research leader at the Institute for Respiratory Health and clinical associate professor at Curtin Medical School, Curtin University, Perth, WA.
Inducible laryngeal obstruction is an important contributor to both undiagnosed breathlessness and poorly controlled asthma.
- More difficulty breathing out- Wheezing( expiratory)- Lower chest tightness / heaviness- Cough— worse in the early morning, or at night, causing nocturnal waking. performed, it is often of substandard quality. 7 Similarly, assessment of airway inflammation through fractional exhaled nitric oxide remains largely inaccessible. 8 This lack of confirmatory testing is also prevalent in respiratory specialists’ rooms. 9
As a result, it is estimated that around one-third of individuals treated for asthma lack objective evidence of the disease when comprehensively assessed. 5, 10 This translates to more than one in 30 Australians receiving treatment for a condition they may not have. 11 This diagnostic inaccuracy has significant implications, including unresolved causes and symptoms, and unnecessary medication use.
Furthermore, even among those with confirmed asthma, there is often a gap between objective physiological measurements and the patient’ s reported symptom burden, as captured by validated patient-reported outcome measures such as the Asthma Control Questionnaire or the Asthma Control Test. 12 This discordance is often attributable to comorbidities including obesity, dysfunctional breathing patterns, and inducible laryngeal obstruction( ILO), which may worsen with the use of sympathomimetics, such as short-acting beta agonists, and systemic corticosteroids.
Narrowing the differential diagnosis
There has been a welcome move towards addressing the‘ Treatable Traits’ of individuals with respiratory disease. 13 This model emphasises identifying objective issues that are treatable and targeting therapy towards those issues. This approach formalises the tailoring of treatment to the individual, making it a natural fit with clinical practice.
Applying a Treatable Traits lens to breathlessness invites us to identify the measurable and specific treatable problems that contribute to an individual’ s symptom complex( see figure 1). The sensation of breathlessness varies in character for given specific drivers, but in most cases it relates to the effort required from the individual to breathe, that is, the mouth pressure they are generating as a proportion of the maximum they can generate, and the frequency of respiration as a proportion of the fastest they can breathe. 14-16 Put simply: the harder you are sucking or blowing, the more breathless you feel.
Airflow obstruction is therefore a major— and often treatable— driver of dyspnoea. Notably, the narrowest part of the airway is at the larynx, which has a cross-sectional area many times smaller than the cumulative cross-sectional area of the small airways of the lung. 17 As such, changes at or around the level of the vocal cords can have a disproportionate impact on the sensation of breathlessness. Identifying and addressing laryngeal airflow limitation is therefore a key treatable trait contributing to breathlessness.
Inducible laryngeal obstruction
ILO, also known as vocal cord dysfunction, is defined as the inappropriate, transient, and reversible narrowing of the larynx in response to triggers. 18
ILO is commonly researched in hospital-presenting populations, who typically have a female predominance. Patients generally present in two key age groups: those in middle adulthood who often present with‘ classic’ features of ILO, and adolescents or young people who usually present with exercise-related symptoms. Populations that are frequently researched include those attending respiratory or asthma outpatient clinics in tertiary hospitals, symptomatic adolescents engaging in sports, or elite-level athletes. Most publications originate from the UK, US, Denmark, Sweden, Norway and Australia. As such, our perspective about who is affected by ILO is skewed, with very few general population studies. This is in part due to the relative invasiveness of gold standard testing, limited access to costly equipment and availability of nasoendoscopists experienced in ILO diagnosis. 19-22
Clinical queries
ILO presents as a rapid-onset severe breathlessness which is generally described as unresponsive to asthma therapies. Associated features may include upper chest tightness, throat discomfort, cough, voice changes and noisy stridor on inspiration that
Inducible laryngeal obstruction( ILO) can mimic— or coexist with— asthma. The symptoms are similar, but probing questions can help distinguish the two.
ILO does not respond to asthma therapies and may be the reason a patient’ s asthma is difficult to control. Objective tests can determine if their symptoms are in excess of their lower airway obstruction.
Referral to a tertiary asthma clinic with a multidisciplinary team including an ILOexperienced speech pathologist can clarify diagnoses, treat the ILO, and improve patient outcomes.
First-line treatment for ILO is speech pathology intervention, not medications or surgery, and is usually successful.
can often be mistakenly described by the patient as‘ wheeze’. Given the similarity of symptoms to asthma, that is, breathlessness,‘ wheeze’, chest tightness and cough, it is unsurprising that ILO is often misdiagnosed as asthma. 23 To further confuse matters, ILO coexists with asthma in 25 % of those with confirmed asthma.
20, 24
Untangling ILO from asthma therefore requires two key approaches: first, a more discerning history, and second, objective testing for both conditions. It is key to note that clinical history alone is insufficient to differentiate between asthma and ILO, and the use of objective tests is crucial to diagnosis and successful management.
Clinicians with ILO experience will usually begin by requesting a full description of an attack, then follow with probing questions aimed at discriminating between asthma and ILO( see table 1).
With regard to the question,“ How quickly does it come on?”, symptoms that appear instantly and build in severity over seconds to minutes are in keeping with an ILO attack. In comparison, symptoms that gradually build over 30 minutes, and peak within 1-2 hours with a slow recovery over hours to days, are more suggestive of an asthma attack.
Another discerning question is,“ What can trigger it?” Patients describe aerosolised deodorants, perfumes, cleaning products, strong odours or mechanical factors like laughing as triggers for ILO. These may be quite different from the typical asthma triggers, which include viruses, cold