What is inducible laryngeal obstruction?

Inducible Laryngeal Obstruction (ILO): A Simple Explanation

Inducible laryngeal obstruction is an inappropriate, temporary narrowing of the voice box (larynx) that occurs in response to specific triggers, causing breathing difficulties that can mimic asthma but involves the upper airway rather than the lungs. 1

What Happens During ILO?

ILO involves the following key features:

• Temporary airway closure: The vocal folds or structures above them inappropriately narrow or close when they should remain open during breathing
• Trigger-induced: Episodes are provoked by specific triggers such as exercise, emotional stress, or irritants
• Reversible: The obstruction resolves once the trigger is removed or addressed
• Breathing difficulty: Causes symptoms like shortness of breath, noisy breathing, and throat tightness

Types and Classification

ILO is classified based on two mandatory domains 1:

1. The inducer (what triggers an episode):

   • Exercise (e.g., during high-intensity training)
   • Emotional stress (e.g., during arguments)
   • Irritants (e.g., exposure to cleaning chemicals)
   • Sometimes the trigger may not be readily identifiable

2. Laryngoscopic findings (what's seen during examination):

   • Location: Glottic (true vocal folds), supraglottic (structures above vocal folds), or both
   • Breathing phase affected: Inspiratory, expiratory, or both
   • Onset pattern: Fast (one breath to next) or slow (over several breaths)
   • Resolution pattern: Fast (<5 minutes) or slow (>5 minutes)

How ILO Differs from Asthma

Many patients with ILO are initially misdiagnosed with asthma 2, 3:

• Location: ILO affects the larynx (voice box), while asthma affects the lower airways (bronchi)
• Response to medication: ILO typically doesn't respond to asthma medications like bronchodilators
• Sound characteristics: ILO often produces inspiratory stridor (noise during inhalation), while asthma typically causes expiratory wheezing
• Onset and resolution: ILO episodes often begin and resolve more suddenly than asthma attacks

Diagnosis

The gold standard for diagnosing ILO is videolaryngoscopy during symptom provocation or during an acute episode 4. This involves:

• Visualizing the vocal folds using a laryngoscope while exposing the patient to their specific trigger
• Documenting the specific pattern of laryngeal obstruction according to the international consensus nomenclature
• Ruling out other conditions that may mimic ILO

Common Pitfalls in ILO Management

• Misdiagnosis as asthma: Studies show that 38.3% of patients diagnosed with asthma may actually have ILO 2
• Inappropriate medication use: Treating ILO with asthma medications is ineffective and may delay proper treatment
• Failure to identify triggers: Not recognizing specific triggers prevents effective management
• Overlooking co-existing conditions: ILO and asthma can occur together, requiring comprehensive assessment

Treatment Approaches

Management of ILO focuses on:

1. Immediate management during episodes:

   • Removal from trigger exposure
   • Breathing techniques to control symptoms
   • Positioning upright to optimize airway patency
   • Reassurance and anxiety reduction 5

2. Long-term management:

   • Teaching specialized breathing techniques
   • Trigger avoidance strategies
   • Coordinated care between pulmonology, otolaryngology, and speech pathology
   • Psychological support if anxiety or stress are contributing factors 5

Understanding ILO is crucial for proper diagnosis and management, especially since it's frequently misdiagnosed as asthma, leading to inappropriate treatment and continued symptoms.