Airway Obstruction

Airway obstruction is a partial or complete blockage of the airways that impedes airflow. An airway obstruction can be classified as upper, central, or lower depending on location. Lower airway obstruction (LAO) is usually a manifestation of chronic disease, such as asthma or chronic obstructive pulmonary disease (COPD). Upper airway obstruction (UAO) and central airway obstruction (CAO) refers to a mechanical blockage of the large airways and are potentially life-threatening events, which need to be recognized and managed promptly.

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Overview

Definition

Airway obstruction is a blockage of the airways, which impedes air flow and effective respiration.

Anatomic classification

  • Upper airway obstruction (UAO):
    • Nasopharynx, larynx, and trachea
  • Central airway obstruction (CAO):
    • Trachea and mainstem bronchi
  • Lower airway obstruction (LAO): 
    • Distal to mainstem bronchi
    • Involves small airways
    • Usually a manifestation of chronic disease

Epidemiology

  • Exact incidence is unknown.
  • Occurs in 20%–30% of patients with lung cancer

Etiology

Upper airway obstruction and CAO (large airway obstruction):

  • Masses:
    • Lung cancer most common
    • Benign masses (papillomas)
  • Aspiration of foreign body
  • Mucous plug
  • Tracheomalacia
  • Angioedema (tongue swelling)
  • Anaphylaxis
  • Obstructive sleep apnea (OSA)
  • Laryngoceles
  • Tracheal strictures/stenosis
  • Airway hematomas (trauma)
  • Extrinsic compressions (e.g., vascular rings, thyroid tumors)
  • Infections

Foreign body stuck between vocal cords (bronchoscopic view)

Image: “Foreign body stuck between vocal cords” by Kamran Mottaghi et al. License: CC BY 3.0

Lower airway obstruction (small airway obstruction):

  • Asthma
  • Chronic obstructive pulmonary disease (COPD)
  • Post-infective bronchial hyperreactivity
  • Bronchiectasis and cystic fibrosis
  • Infections:
    • Allergic bronchopulmonary aspergillosis
    • Endobronchial tuberculosis

Pathophysiology

Mechanisms

  • Extrinsic or intrinsic compression due to tumors
  • Endobronchial granulation tissue or calcifications
  • Thinning or collapse of the airway wall due to tracheomalacia
  • Airway edema due to infection, inflammation, or bleeding

Chronic and subacute

  • Minor obstruction is often asymptomatic initially.
  • Can be caused by a mass, a stricture, or external compression
  • Can be exacerbated by exertion, increased ventilatory demands (e.g., pneumonia), or progressive obstruction; and then become acute

Acute

  • Precipitating events:
    • Foreign body aspiration
    • Mucous plug
    • Laryngotracheal trauma
    • Smoke inhalation
    • Pediatric infections:
      • Epiglottitis
      • Croup
      • Tonsillar or retropharyngeal abscess
      • Diphtheria
  • Acute exacerbation of mild chronic obstruction in the setting of swelling, bleeding, or increased secretions

Clinical Presentation

Chronic and subacute

  • Symptoms are non-specific:
    • Dyspnea
    • Wheezing
    • Cough
    • Hemoptysis
    • Hoarseness
    • Chest pain
  • Frequently misdiagnosed as asthma/COPD
  • Diagnostic clues:
    • Positional symptoms rather than diurnal (day vs. evening)
    • Inspiratory wheeze (stridor)
    • History of intubation or tracheal disease (tracheal stenosis)

Acute

  • Acute onset tachypnea
  • Tachycardia
  • Inspiratory stridor
  • Wheezing
  • Increased respiratory effort: suprasternal retractions, nasal flaring, grunting
  • Gagging, gasping
  • Cyanosis
  • Obtunded mental status

Diagnosis

History

History can be obtained from a responsive patient not in extremis.

  • Does the patient have a history of:
    • Respiratory disease
    • Lung or head/neck cancer
    • Foreign body aspiration
    • Previous intubation/tracheostomy
    • Neck surgery

Physical exam

  • General: 
    • Cyanosis
    • Pulse oximetry < 90%
    • Facial/neck swelling
    • Signs of respiratory distress (tachypnea, nasal flaring, gasping, use of accessory muscles)
  • Direct inspection of the airways:
    • Visual inspection (angioedema, foreign body)
    • Laryngoscopy
    • Bronchoscopy

Imaging

  • Should only be performed after airway stabilization
  • Chest X-ray:
    • Mass
    • Tracheal deviation
    • Mediastinal shift
    • Endobronchial luminal defect
  • Neck X-ray:
    • Thumbprint sign for epiglottitis
  • Chest computed tomography (CT):
    • More detailed imaging than X-ray
  • Magnetic resonance imaging (MRI):
    • For vascular pathology
    • Soft tissue tumors (e.g., sarcomas)

Pulmonary function test (PFT)

For chronic/subacute symptoms in the setting of suspected obstruction:

  • Minimal variability in peak flow/spirometry
  • Characteristic “squared-off” flow-volume loop 
  • Fall in peak expiratory flow rate (PEFR) relatively greater than fall in forced expiratory volume in 1 second (FEV1)

Management

Life-threatening obstruction

  • If a foreign body is suspected, abdominal thrusts (Heimlich maneuver) or back slaps (for infants) should be performed for responsive patients.
  • Cardiopulmonary resuscitation is initiated for unresponsive patients.
  • The goal of initial management:
    • Provide adequate oxygenation
    • Secure airway
  • The initial step is bag-mask ventilation.
  • Maneuvers to help open the airway:
    • Head tilt-chin lift (if no cervical spine trauma is suspected)
    • Jaw-thrust (allows airway opening without disturbing the cervical spine)
  • Endotracheal intubation is the definitive airway management.
  • If intubation cannot be accomplished:
    • A laryngeal mask can be inserted if obstruction is from a swollen tongue.
    • Emergent cricothyroidotomy or tracheostomy
    • Rigid bronchoscopy and retrograde intubation may be needed in case of bronchial obstruction.

The abdominal thrusts (Heimlich) anti-choking maneuver

Image: “The abdominal thrusts (Heimlich) anti-choking maneuver” by US ARMY MEDICAL DEPARTMENT CENTER AND SCHOOL FORT SAM HOUSTON. License: Public Domain

Not immediately life-threatening obstruction

  • History, laboratory, and imaging evaluations can be obtained.
  • Initial management:
    • Sit the patient up.
    • High-flow oxygen or heliox (a mixture of oxygen and helium) via a mask
    • Intravenous high-dose corticosteroids (reduce edema around the obstruction)
    • Nebulized salbutamol and adrenaline
    • Intravenous fluid replacement
  • Definitive management depends on the underlying cause.

Differential Diagnosis

  • Chronic obstructive pulmonary disease: chronic obstructive inflammation of the small airways and changes in the lung parenchyma and pulmonary vasculature. Patients usually present with dyspnea and chronic cough. COPD is a progressive condition with acute flares. Management includes smoking cessation, pulmonary rehabilitation, and pharmacotherapy.
  • Asthma: chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. Patients typically present with wheezing, cough, and dyspnea. Diagnosis is confirmed with a PFT showing a reversible obstructive pattern. Treatment, based on symptom severity, includes bronchodilators and inhaled corticosteroids for control of inflammation.

References

  1. Aboussouan, L. S., & Stoller, J. K. (1994). Diagnosis and management of upper airway obstruction. Clinics in chest medicine, 15(1), 35–53. https://pubmed.ncbi.nlm.nih.gov/8200192/
  2. Herth F. JF. (2020).  Clinical presentation, diagnostic evaluation, and management of central airway obstruction in adults. Retrieved 25 January 2021, from https://www.uptodate.com/contents/clinical-presentation-diagnostic-evaluation-and-management-of-central-airway-obstruction-in-adults
  3. Loftis L.L. (2019). Emergency evaluation of acute upper airway obstruction in children. Retrieved 25 January 2021, from https://www.uptodate.com/contents/emergency-evaluation-of-acute-upper-airway-obstruction-in-children
  4. Wittels K. (2019). Basic airway management in adults. Retrieved 26 January 2021, from https://www.uptodate.com/contents/basic-airway-management-in-adults

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