Airway obstruction

An upper airway or central airway obstruction can be rapidly fatal. Stridor is a common clinical feature of airway obstruction and is a red flag for respiratory failure and difficult airway management. Patients with respiratory distress or signs of respiratory failure require immediate airway management, respiratory support, and/or treatment of rapidly reversible causes of airway obstruction. Upper airway obstruction is often managed with endotracheal intubation. Central airway obstruction may require rigid bronchoscopy, flexible bronchoscopy, and/or endobronchial intubation. Advanced evaluation and diagnostic testing are done only after securing the airway and/or excluding life-threatening causes of airway obstruction. Airway obstruction may be caused by infectious, inflammatory, or structural changes in the airway and/or neuromuscular conditions that reduce airway patency. Airway obstruction is diagnosed clinically, but airway endoscopy and imaging may be necessary to determine the specific etiology. Definitive treatment is based on the underlying cause.

Distal airway obstruction involving bronchioles and/or alveoli usually manifests with wheezing, and the causes and progression vary from those of upper and central airway obstruction. The approach and management of wheezing are discussed separately.

Upper airway ^[1][2]

• The airway between the nares and the larynx
• Includes nasopharynx, oropharynx, hypopharynx, and larynx
• All portions are extrathoracic.

Lower airway ^[1][2][3][4]

• A broad term for the central airway and the distal airway
• Structures included in the lower airway vary depending on the source and the context.
  • Epiglottis or upper larynx (overlaps with some definitions of the upper airway)
  • Trachea and bronchi (overlaps with the central airway)
  • Bronchioles and alveoli (overlaps with the distal airways and some definitions of the lung parenchyma)

Definitions of the beginning of the lower airway vary and range from the epiglottis to the distal larynx. The central airway begins with the trachea.

Central airway ^[3]

• Major airway structures distal to the larynx
• Typically includes the trachea and mainstem bronchus ^[4]
• The upper trachea is extrathoracic; all other portions are intrathoracic.

Obstruction of the upper airway or central airway is a medical emergency that can cause respiratory failure and death.

Distal airway ^[5]

• Airway from the eighth-generation bronchioles to the alveoli
• Lacks cartilaginous support.
• Airway collapse, not intraluminal obstruction, is most often the cause of the obstruction.
• See “Wheezing in children,” “Asthma,” and “Acute exacerbation of COPD.”

Stridor is a risk factor for a difficult airway.

• Perform an ABCDE survey and allow the patient to assume a position of comfort.
• If signs of airway obstruction and impending respiratory failure are present:
  • Begin high-flow nasal cannula oxygen therapy. ^[1]
  • Prepare for a difficult airway.
  • Begin basic airway management.
  • Consult anesthesia and/or otolaryngology urgently.
  • Manage the difficult airway.
• Consult pulmonology urgently if clinical features of central airway obstruction are present. ^[4]
• Treat rapidly reversible causes of airway obstruction with, e.g.:
  • IM epinephrine for anaphylaxis
  • Antidotes for sedative-hypnotic overdose (e.g., naloxone for opioid overdose)
  • Racemic epinephrine for croup
  • Maneuvers to dislodge an aspirated FB
  • Consider systemic steroids for acute airway edema (off-label).
• Consider heliox in nonintubated patients. ^[3]
• Obtain etiology-specific diagnostics and manage the underlying cause.

Avoid unnecessary procedures that may increase agitation and worsen turbulent airflow, especially in children. ^[6]

Consider transporting stable patients to the operating room for intubation.

Use age to help narrow potential diagnoses. Laryngomalacia and vocal fold immobility (e.g., vocal cord paralysis) are common in infants; foreign body aspiration and croup are common in young children. ^[7]

Infectious ^[4][6]

Acute

• Croup
• Epiglottitis
• Diphtheria
• Bacterial tracheitis
• Retropharyngeal abscess
• Tetanus

Chronic

• Tuberculosis
• Fungal infections

Allergic or inflammatory ^[4][6]

Acute

• Spasmodic croup
• Angioedema
• Anaphylaxis
• Smoke inhalation injury
• Exposure to irritants and asphyxiants
• Aspiration pneumonitis

Chronic

• Granulomatosis with polyangiitis
• Amyloidosis
• Sarcoidosis

Structural ^[6]

Acute

• Acute aspiration
  • Foreign body aspiration (FBA)
  • Excessive vomiting (especially if risk factors for aspiration are present)
  • Hematemesis
• Trauma
  • Blunt neck trauma
  • Penetrating neck injury
  • Laryngeal fracture
  • Facial fractures
  • Soft tissue injuries of the head and neck
• Edema (e.g., postextubation laryngeal edema)
• Massive hemoptysis
• Airway stent dislodgment

Chronic

• Tumors
  • Pharyngeal cancer
  • Laryngeal cancer
  • Subglottic hemangioma
  • Mediastinal masses
  • Endobronchial lung cancer
  • Goiter
• Obstructive sleep apnea
• Airway malacias (e.g., tracheomalacia, laryngomalacia)
• Laryngotracheal stenosis (e.g., after prolonged intubation, radiation therapy, lung transplant)
• Laryngeal papillomatosis
• Congenital anomalies
  • Micrognathia
  • Pierre Robin syndrome
  • Treacher Collins syndrome
  • Macroglossia
  • Down syndrome
  • Choanal atresia
  • Thyroglossal duct cyst
  • Lingual thyroid
  • Laryngocele
  • Double aortic arch

Neuromuscular impairment

Systemic conditions that impair airway protective reflexes may also decrease airway patency.

• Causes of altered mental status and coma
  • Traumatic brain injury
  • Sedative-hypnotic drug overdose
  • Stroke
• Laryngospasm
• Vocal cord paralysis
• Neuromuscular weakness with bulbar dysfunction
  • Guillain-Barré syndrome, especially Miller-Fisher syndrome
  • Myasthenia gravis
  • Botulism

Clinical features of partial airway obstruction ^[8]

• Stridor
• Noisy breathing
• Stertor
• Hoarse voice
• Gurgling from secretions
• Hypoxia or hypercarbia
• Signs of increased work of breathing

Clinical features of complete airway obstruction ^[8]

• Inability to speak or cough
• Inaudible breaths
• Paradoxical movement of the chest and abdomen
• Profound hypoxia

Clinical features of central airway obstruction ^[3][4]

• Dyspnea and stridor (most common)
• Prolonged and/or gradual onset of symptoms
• Unilateral wheezing
• Worsens with exercise ^[3]
• Late signs: dyspnea at rest, cough, wheezing, diminished sputum production ^[3]

Central airway obstruction is easy to misdiagnose because it is less common than other lower airway diseases (e.g., asthma) but has similar clinical features. ^[4]

Stridor ^[9]

Stridor is a harsh, high-pitched vibratory breath sound produced by upper airway obstruction.

• Inspiratory stridor
  • Typically caused by extrathoracic airway obstruction, most commonly at or above the glottis
  • Characteristic of epiglottitis, spasmodic croup, upper airway FBA, bilateral vocal cord palsy
• Expiratory stridor
  • Suggests intrathoracic tracheal obstruction
  • Characteristic of lower airway FBA, tracheal cancer
• Inspiratory and expiratory (biphasic) stridor: suggests a fixed obstruction, typically glottic or subglottic

Although stridor is a key clinical feature of airway obstruction, it does not always occur.

Stertor ^[10][11]

• Definition: a low-pitched flapping or snoring sound caused by nasal or nasopharyngeal obstruction ^[10][11]
• Common causes
  • Laryngomalacia
  • Nasal foreign body
  • Nasal congestion
  • Adenoid hypertrophy
  • Nasal turbinate hypertrophy
  • Nasolacrimal duct cyst
  • Obstructive sleep apnea

Wheezing

• Definition: A prolonged, musical, high-pitched sound most commonly heard during expiration and typically caused by distal airway obstruction
• Common causes
  • Asthma exacerbation
  • COPD exacerbation
  • Anaphylaxis
  • Bronchopneumonia
  • Bronchiolitis
  • Lower airway FBA
  • Congestive heart failure
  • See also “Wheezing in children.”

Differentiating wheezing from expiratory stridor is difficult. Wheezing is a musical sound produced primarily during expiration, whereas expiratory stridor is typically a single harsh, high-pitched expiratory sound. ^[12]

A focused history and physical examination can narrow potential diagnoses and facilitate the choice of diagnostic testing. ^[6][9]

Focused history

• Onset: acute or chronic
• Prior events
  • Choking episode or aspiration event
  • URI or febrile illness
  • Sore throat
  • Dysarthria, dysphonia
  • Dysphagia or feeding difficulties
  • Previous intubation and/or airway trauma or surgery
• Exacerbating factors
  • Nighttime
  • Eating
  • Supine position
  • Crying or strenuous activity
  • URI
• Associated symptoms
  • Drooling
  • Barking cough
  • Muffled voice or cry
  • Weak voice or cry
  • Cyanosis
  • Neck stiffness
  • Torticollis
  • Constitutional symptoms

Focused physical examination

• Clinical features of airway obstruction
• Clinical features of respiratory failure
• Respiratory phase of stridor (if present)
• Lung auscultation
• Head and neck examination, including:
  • Hard signs of penetrating neck injury
  • Features of blunt neck trauma

Do not assume decreasing stridor is a reassuring sign. Respiratory failure due to decreased airflow may be imminent. ^[10]

Airway obstruction is diagnosed clinically; the suspected etiology and the patient's clinical status guide the choice of diagnostic testing. ^[9][10]

Airway endoscopy

Direct visualization of the airway can provide a definitive diagnosis. Endoscopy may also be used for definitive management (e.g., removal of a foreign body or excision of an airway mass).

• Fiberoptic laryngoscopy
• Video laryngoscopy
• Rigid bronchoscopy
• Flexible bronchoscopy

Perform a diagnostic bronchoscopy in all patients with symptomatic central airway obstruction. ^[13]

Imaging ^[6][9]

Imaging can be helpful to assess for anatomical abnormalities, foreign bodies, or infection (e.g., abscesses).

• X-ray neck and chest (lateral and AP views)
  • Steeple sign (AP view of neck and chest) suggests croup.
  • Thumbprint sign (enlarged epiglottis looks like a thumb on a lateral neck x-ray) suggests epiglottitis.
  • Nonspecific subglottic narrowing or irregularities of the anterior trachea on neck x-ray may occur with bacterial tracheitis.
  • Radiolucent foreign bodies may be visible in any view.
  • Asymmetrical lung inflation suggests a foreign body in a bronchus.
• CT or MRI neck and/or chest
  • To confirm x-ray findings or guide surgical management.
  • May demonstrate airway mass or inflammation
• Neuroimaging may be indicated to determine the underlying cause of a functional airway obstruction.

A CT should be obtained in all patients with suspected central airway obstruction. ^[3][4][13]

Ensure the airway is protected or an airway specialist is immediately available when obtaining imaging. Sedation and/or supine position may cause complete airway obstruction. ^[6]

Laboratory studies ^[6][14]

Routine testing is not recommended for airway obstruction, but studies may confirm the etiology and guide management.

• Respiratory viral panel: to identify a causative virus
• CBC: to help distinguish between bacterial and viral infections
• Blood gas analysis: to assess for hypoxemia and/or hypercarbia
• Diagnostics for altered mental status and diagnostics for neuromuscular weakness: may be required to investigate the underlying cause of functional airway obstruction

Pulmonary function testing (PFTs) ^[3][4]

• Indication: unclear location and/or nature of an airway obstruction in a stable patient
• Findings
  • Flattening of only the inspiratory loop suggests a variable extrathoracic obstruction (i.e., upper airway or upper trachea).
  • Flattening of only the expiratory loop suggests a variable intrathoracic obstruction (i.e., lower trachea or bronchus).
  • Flattening of both loops suggests a fixed airway obstruction in any location.
  • See “Pulmonary function testing” for flow volume loops in chronic obstructive lung disease (i.e., distal airway pathology).

Do not obtain spirometry and PFTs in patients with respiratory distress or advanced disease; these tests may lead to acute respiratory failure. ^[3]

Acquired

Congenital

• Follow the ABCDE approach.
• If clinical features of obstructed airway and/or clinical features of respiratory failure are present:
  • Prepare for a difficult airway.
  • Begin basic airway management.
  • Consult anesthesia and/or otolaryngology urgently.
  • Consider transport to the operating room for airway management.
  • Manage the difficult airway.
• Consult pulmonology urgently if clinical features of central airway obstruction are present.
• Perform a focused clinical evaluation for airway obstruction.
• Obtain etiology-specific diagnostics and initiate treatment.
• Admit patients at risk of progressive airway obstruction or continued respiratory distress.

Disposition is based on etiology and severity of symptoms. Consider admission for patients with: ^[6][10]

• Ongoing respiratory distress
• Risk of progressive, recurrent, and/or refractory airway obstruction
• Presence of admission criteria for croup
• Bacterial tracheitis
• Epiglottitis
• FBA
• Persistent AMS or neuromuscular weakness
• Aspiration pneumonitis
• Head and neck cancers or mediastinal masses requiring definitive airway management (e.g., tracheostomy)

Follow the initial management of airway obstruction for all patients. Further management is based on the specific cause of the obstruction.

Upper airway obstruction treatment ^[1]

• Ensure a safe airway and adequate oxygenation.
  • Endotracheal intubation bypasses upper airway obstructions.
  • Often requires difficult airway management
  • An emergency surgical airway or planned surgical airway may be required for complete obstruction or failed intubation.
• Treat the underlying cause of obstruction.
• Monitor for the effectiveness of treatment and/or potential recurrence of obstruction with serial examinations.

Complete airway obstruction can recur immediately after endotracheal tube removal. Be prepared for reintubation when extubating patients with airway obstruction.

Central airway obstruction treatment ^[3][4][13]

Therapeutic bronchoscopy

• Clinical applications
  • Endobronchial intubation (rigid bronchoscopy only): allows immediate ventilation past a complete tracheal obstruction
  • Tumor resection (e.g., electrocautery, argon laser, cryotherapy)
  • Airway dilation
  • Control of massive hemoptysis and removal of obstructing clot
  • Removal of a central airway foreign body
  • Airway stent placement or repositioning
• Techniques
  • Rigid bronchoscopy
    • Performed in the operating room with anesthesia
    • Conventional or jet ventilation is possible during the procedure.
    • The large operating channel provides good access for suctioning and tumor resection.
    • Can be pushed past a large tumor for immediate relief of airway obstruction
  • Flexible bronchoscopy
    • May be performed outside the operating room with procedural sedation
    • Allows better visualization of smaller airways than with rigid bronchoscopy
    • Oxygenation is possible through the endoscope but ventilation is not.
    • Suctioning and tumor resection are limited.

Surgery

• Tumor resection
• Resection of the stenotic portion of the airway

Adjunct treatment

• Radiation therapy: external beam or brachytherapy
• Chemotherapy: systemic or topical