Airway Obstruction

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

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.

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.