HNS36 Infectious Causes Of Upper Airway Obstruction

Question 1

Upper and Lower respiratory tract

Answer 1

Upper:

• Nasal cavity
• Pharynx (Nasopharynx, Oropharynx (narrow), Laryngopharynx (narrow))
• Larynx

Lower:

• Trachea
• Bronchi
• Lungs

Question 2

Acute epiglottitis - Infection in Oropharynx

Answer 2

Causative agent:

1. ***Haemophilus influenzae type B
   - Gram -ve coccobacilli
   - require both X (haemin) + V (NAD) factors
   - 6 types (a-f) / nontypeable
   - beta-lactamase producing

Group:
- Children 2-4 years old

Clinical features:

1. Fever (rapid onset: 6-12 hours)
2. Severe sore throat
3. ***Dysphonia
4. ***Drooling oral secretion
5. ***Stridor

Diagnosis:

1. Laryngoscopy: “Cherry-red” epiglottis
2. Neck X-ray: ***“Thumb” sign (do NOT wait for X-ray) —> Enlarged epiglottis
3. Blood culture
4. DO NOT take swab before laryngoscopy —> swab can further aggravate inflammation

Management:

1. Airway protection (Intubation, Tracheostomy)
2. Antibiotic e.g. ***Amoxicillin-clavulanate
3. ***Rifampicin prophylaxis if unvaccinated contact <= 4 years in household

Question 3

Peritonsillar abscess (Quinsy) - Infection in Oropharynx

Answer 3

Causative agents:

1. ***Group A streptococcus (Streptococcus pyogenes)
2. Mixed (Oropharyngeal organisms: Viridans Streptococcus, Anaerobes)

Group:

• Adolescents
• Young adults

Clinical features:

1. Severe sore throat
2. Low grade fever
3. ***Dysphagia
4. Inflammation of peritonsillar area with ***medial displacement of tonsil
5. Bilateral —> airway obstruction —> Stridor

Management:

1. Airway protection
2. Antibiotic
3. Drainage of abscess

Question 4

Streptococcus

Answer 4

Gram +ve cocci in ***chains

1. α haemolytic (green discolouration)
   —> Streptococcus pneumoniae (Optochin sensitive, Bile soluble)
   —> Viridans Streptococcus (Optochin resistant, Bile insoluble)
2. β haemolytic (clear zone of haemolysis)
   - Lancefield grouping:
   —> Group A (Streptococcus pyogenes) (sensitive to Bacitracin) —> Acute pharyngitis
3. γ haemolytic (no clear zone)

Question 5

Deep fascial space infections - Infection in Oropharynx

Answer 5

3 major deep space:

1. Submandibular and Sublingual space —> Ludwig’s angina
   - Floor swelling
2. Lateral pharyngeal / Parapharyngeal space
   - Jaw angle swelling
   - Anterior (close to masticator): Pain +++, Trismus +++
   - Posterior (airway most narrow): Dyspnea +++
3. Retropharyngeal space (anterior to vertebral column)
   - Posterior pharynx swelling

Question 6

Submandibular and Sublingual space infection (Ludwig’s angina: Pain in chest —> mimic angina)

Answer 6

Causative agents:
1. Mixed oral flora —> Underlying ***dental root abscess (50-90%)

Clinical features:

1. ***Board-like (hard) swelling involving bilateral submandibular and sublingual spaces
2. High fever, systemic toxicity
3. Mouth held open
4. Dysphagia

Management:

1. Airway protection
2. Antibiotic
3. ***Soft tissue decompression (removal of infected tissue)
4. ***Dental assessment

Question 7

Lateral pharyngeal / Parapharyngeal space infections

Answer 7

Causative agents:
Pathogens from primary site
—> Underlying spread of infection from adjacent structures
—> ***Odontitis, Pharyngitis, Tonsillitis, Parotitis, Otitis, Mastoiditis

Clinical features:

1. Fever
2. Sore throat
3. Dysphagia
4. Neck stiffness

Life-threatening complications (spread through Carotid sheath):
1. Jugular vein thrombophlebitis (Lemierre syndrome) (Internal jugular)
—> Fusobacterium necrophorum
—> Multifocal pneumonia / Lung abscess
2. ***Carotid artery erosion (Internal carotid)

Investigations:

1. CT/MRI (to assess extent of infection)
2. Blood culture
3. Pus culture

Management:

1. Airway protection
2. Antibiotic
3. +/- Drainage
4. ***Treat primary infective focus

Question 8

Retropharyngeal space infections

Answer 8

Causative agents:
Pathogens from primary site (**Odontitis, Peritonsillar abscess, **Cervical vertebral osteomyelitis, Perforated pharynx)
—> Mixed **oral flora (from pharynx / dental source)
—> **Staphylococcus aureus (from vertebral osteomyelitis)

Clinical features:

1. Fever
2. Sore throat
3. Dysphagia
4. Neck stiffness

Complications:
- ***Mediastinitis: spread of infection along space (difficult to treat)

Investigations:

1. Neck X-ray (***Prevertebral soft tissue swelling)
2. CT (to assess extent of infection)
3. Blood culture
4. Pus culture

Management:

1. Airway protection
2. Antibiotic
3. +/- Drainage

Question 9

Relationships between 3 major deep space

Answer 9

Submandibular and Sublingual space
—> connected to Lateral pharyngeal space
—> connected to Carotid sheath
—> both linked to Retropharyngeal space
—> along space —> Mediastinum

Question 10

Croup (Laryngotracheobronchitis) - Infection in Larynx

Answer 10

Infection of larynx (vocal cord) + trachea + bronchi

Causative agents (VIRUS):

1. Parainfluenza virus
2. Influenza virus
3. RSV
4. Adenovirus
5. Rhinovirus
6. Mycoplasma

Group:
- Young children (3 months - 3 years) (most common cause of ***stridor in children)

Clinical features:

1. URI symptoms (slow onset / prodromal symptom: 2-3 days)
2. Fever
3. Hoarseness
4. ***Barking cough
5. ***Stridor
6. ***Tripod position

Investigations:

1. Neck X-ray: **Subglottic swelling, Hourglass, **Steeple sign
2. Nasopharyngeal aspirate (NPA): for respiratory virus antigens

Management:

1. Airway protection
2. Racemic ***Adrenaline (dilate airway)
3. ***Steroid (↓ oedema)
4. NO antibiotic (∵ viral infection)

Question 11

Comparison between Acute epiglottitis and Croup

Answer 11

Acute epiglottitis (***Supraglottic):

• ***Haemophilus influenzae type B
• 2-4 years
• toxic and unwell
• abrupt onset
• high fever
• minimal/absent cough
• unable to speak
• drooling saliva

Croup (***Subglottic):

• ***VIRUS
• 3 month - 3 years
• well looking
• ***viral prodrome
• moderate fever
• ***barking cough
• hoarse voice
• ***able to swallow

Question 12

Summary of infectious causes of upper airway obstruction

Answer 12

Oropharynx:

1. Acute epiglottitis
2. Bilateral peritonsillar abscess (Quinsy)
3. Deep fascial space infections
   - Submandibular and Sublingual space
   - Lateral pharyngeal / Parapharyngeal space
   - Retropharyngeal space
4. Diphtheria (Corynebacterium diphtheriae, pseudomembrane)
5. EBV infectious mononucleosis (anginose (severe) form)

Larynx:
1. Croup (Laryngotracheobronchitis)

Others:
1. Secondary infections complicating conditioning mucositis (after conditioning chemotherapy)

Question 13

Non-infectious causes of upper airway obstruction

Answer 13

More common than infectious causes!!!

1. ***Foreign body aspiration
2. ***Tumour
3. Bilateral vocal cord palsy
4. Goitre
5. Angioneurotic edema
6. Subcutaneous emphysema

Always secure airway before making differential diagnosis!!!