Flow-volume loops in different types of physiologic airway obstruction
The configuration of the flow-volume loop can help distinguish the site of airway narrowing. The airways are divided into intrathoracic and extrathoracic components by the thoracic inlet.
(A) Normal flow-volume loop: the expiratory portion of the flow-volume curve is characterized by a rapid rise to the peak flow rate, followed by a nearly linear fall in flow. The inspiratory curve is a relatively symmetrical, saddle-shaped curve.
(B) Dynamic (or variable, nonfixed) extrathoracic obstruction: flow limitation and flattening are noted on the inspiratory limb of the loop.
(C) Dynamic (or variable, nonfixed) intrathoracic obstruction: flow limitation and flattening are noted on the expiratory limb of the loop.
(D) Fixed upper airway obstruction (can be intrathoracic or extrathoracic): flow limitation and flattening are noted in both the inspiratory and expiratory limbs of the flow-volume loop.
(E) Peripheral or lower airways obstruction: expiratory limb demonstrates concave upward, also called "scooped-out" or "coved" pattern.1. What is Inducible Laryngeal Obstruction (ILO)?
- Answer: ILO is a condition characterized by inappropriate, transient, and reversible narrowing of the larynx in response to external triggers. This leads to symptoms like stridor and can be mistaken for asthma.
2. What are common terms associated with ILO?
- Answer: ILO is also known as paradoxical vocal fold motion, laryngeal dyskinesia, vocal cord dysfunction (VCD), and periodic laryngeal obstruction.
3. What are the primary triggers of ILO?
- Answer: ILO can be triggered by exercise, inhaled irritants, emotional stress, post-extubation, and sometimes laryngopharyngeal reflux. It may also be idiopathic in some cases.
4. How does ILO differ from asthma?
- Answer: Although ILO symptoms can resemble asthma, including wheezing and difficulty breathing, it differs because ILO typically presents with inspiratory stridor, not expiratory wheezing. Additionally, ILO does not respond to bronchodilators, and pulmonary function tests may be normal between episodes.
5. What are the key clinical symptoms of ILO?
- Answer: Patients with ILO often present with dyspnea, throat tightness, stridor, dysphonia, and sometimes cough or dysphagia. Stridor may be heard on inspiration, expiration, or both and is typically loudest over the neck.
6. How is ILO diagnosed?
- Answer: The gold standard for diagnosing ILO is laryngoscopy during an episode. This allows direct visualization of abnormal vocal fold motion and helps rule out other causes of airway obstruction.
7. What role does pulmonary function testing (PFT) play in evaluating ILO?
- Answer: PFTs, especially with flow-volume loops, may show inspiratory flattening suggestive of extrathoracic airway obstruction. However, PFTs alone cannot confirm or exclude ILO; laryngoscopy is essential for diagnosis.
8. How can exercise-induced laryngeal obstruction (EILO) be evaluated?
- Answer: Continuous laryngoscopy during exercise is the preferred method for diagnosing EILO. This allows real-time visualization of laryngeal motion during exercise, which can help confirm EILO.
9. What is the differential diagnosis for ILO?
- Answer: The differential diagnosis includes asthma, laryngospasm, laryngeal angioedema, vocal fold motion abnormalities, laryngotracheal stenosis, and dynamic airway collapse (e.g., tracheomalacia, laryngomalacia).
10. What are initial management strategies for an acute episode of ILO?
- Answer: Initial management includes reassurance, supportive care, and panting maneuvers, which can help open the vocal folds. In severe cases, continuous positive airway pressure (CPAP) or helium-oxygen (heliox) mixtures may be used.
11. What are the long-term management strategies for ILO?
- Answer: Long-term management involves speech-behavioral therapy, avoidance of laryngeal irritants, and sometimes psychotherapy for patients with psychosocial triggers. A multidisciplinary approach is recommended for complex cases.
12. What is the role of speech-behavioral therapy in ILO?
- Answer: Speech-behavioral therapy helps patients control their breathing and manage episodes. Techniques include respiratory retraining, whole-body relaxation, and vocal hygiene. Speech-language pathologists may use biofeedback with videolaryngoscopy during therapy sessions.
13. How are psychosocial factors managed in patients with ILO?
- Answer: Psychotherapy may be beneficial for patients with psychosocial triggers, as it can help them identify and manage stressors that exacerbate ILO.
14. When is botulinum toxin considered in the treatment of ILO?
- Answer: Botulinum toxin injections may be used in refractory cases of ILO, particularly when symptoms are severe and unresponsive to speech therapy. It is often combined with speech and psychological therapies.
Given the associated risk of {{c1::vocal cord dysfunction}} postoperatively, patients who have had a prior {{c2::anterior cervical approach surgery::surgery}} may need to undergo a preoperative ENT evaluation with {{c3::laryngoscopy}}.
to assess for preoperative vocal cord function.
In one study, they found that 17.3% of patients had abnormal findings on laryngoscopic exam which affected decisions regarding approach for revision ACDF
In one study, they found that 17.3% of patients had abnormal findings on laryngoscopic exam which affected decisions regarding approach for revision ACDF
due to adduction of vocal cords during inspiration
Asthma symptoms that fail to respond to typical asthma therapy is suggestive of {{c1::vocal cord dysfunction::diagnosis}}
What type of upper airway obstruction is depicted by the following flow-volume loop?
{{c1::Variable extrathoracic obstruction}}
- Expiratory part is normal (obstruction is pushed outwards by force of expiration)
- During inspiration, the obstruction is sucked into the trachea with partial obstruction and flattening of the inspiratory part of the flow volume loop; results in inspiratory stridor
Flattening of the top and bottom of a pulmonary flow volume curve is characteristic of what?
{{c1::Fixed upper-airway obstruction
Eg, laryngeal edema secondary to a food allergy.}}
What is the likely diagnosis given the flow-volume loop below?
{{c1::Fixed upper airway obstruction (e.g. laryngeal edema)}}
characterized by flattening of the top and bottom of the curve due to decreased airflow rate during inspiration and expiration
What type of upper airway obstruction is depicted by the following flow-volume loop?
{{c1::Fixed upper airway obstruction}}
- In these conditions, the fixed mass impairs both inspiration and expiration
- in diagnosing upper airway obstruction in patients with goiters, flow volume loops the most appropriate method
What type of upper airway obstruction is seen in vocal cord paralysis / dysfunction and laryngeal tumors?
{{c1::Variable extrathoracic obstruction}}
When a vocal cord is paralyzed, it moves passively with pressure gradients across the glottis; during forced inspiration it is drawn inward (impairs inspiration), during forced expiration it is passively blown aside (does not impair expiration)
On flow-volume loop =
characterized by flattening of the top and bottom of the curve due to decreased airflow rate during inspiration and expiration
What type of upper airway obstruction is seen in tracheomalacia and bronchogenic cysts?
{{c1::Variable intrathoracic obstruction}}
In tracheomalacia; during a forced inspiration, negative pleural pressure holds the floppy trachea open; during a forced expiration, loss of structural support results in tracheal narrowing and plateau of diminished flow
On flow-volume loop =
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