Stridor is a high-pitched sound due to turbulent airflow through a partially obstructed airway. ^[1]

From first principles: when a tube's lumen narrows, flow velocity increases (Venturi effect), and once Reynolds number exceeds ~2000, laminar flow becomes turbulent, producing audible vibration. In the extrathoracic airway, during inspiration negative intrathoracic pressure is transmitted to the airway, which tends to collapse extrathoracic structures inward — hence extrathoracic obstruction worsens on inspiration (inspiratory stridor). During expiration, positive intrathoracic pressure compresses intrathoracic airways — hence intrathoracic obstruction worsens on expiration (expiratory wheeze). ^[2]

• Stridor: high-pitched, from laryngeal/tracheal level — implies narrowing of the airway at or below the larynx
• Stertor (snoring): low-pitched, from above the larynx (nasopharynx/oropharynx) — e.g., adenotonsillar hypertrophy, tongue base prolapse ^[1]

• Neonates are obligate nasal breathers — bilateral choanal atresia is therefore an ENT emergency ^[1]
• The paediatric airway is narrowest at the cricoid ring (subglottis), not at the glottis as in adults; even 1 mm of mucosal oedema dramatically increases resistance (resistance ∝ 1/r⁴ by Poiseuille's law)
• Cartilage is softer and more collapsible (laryngomalacia)

Laryngomalacia, Vocal cord palsy, Subglottic stenosis, Congenital tumour/cyst, Subglottic haemangioma, Vascular & lymphatic malformation, Tracheal anomaly, Craniofacial abnormalities, Choanal atresia

Croup, Epiglottitis, Retropharyngeal abscess, Recurrent respiratory papillomatosis, Obstructive sleep apnoea, Foreign body

Tumour, Infection, Bilateral vocal cord palsy, Trauma, Foreign body, Anaphylaxis, Obstructive sleep apnoea

Unstable patients need immediate resuscitation or intubation ^[1]

Perinatal history, Birth history, Age of onset, Aggravating factors, Voice/cry, Choking/feeding, History of intubation

Why each matters:

• Perinatal history: maternal infections (HPV → RRP), birth trauma (vocal cord palsy), prematurity (subglottic stenosis from intubation)
• Age of onset: stridor from birth = congenital cause; onset at weeks-months = laryngomalacia or haemangioma; acute onset = infection or foreign body
• History of intubation: acquired subglottic stenosis is the commonest acquired cause of subglottic narrowing

Phase of stridor, Signs of respiratory distress (respiratory rate, suprasternal/subcostal insucking, nasal flaring, agitation, fatigue, decreased consciousness), Fever, Cyanosis, Position of child, Craniofacial anomaly, Neck swelling, Cutaneous haemangioma, Auscultation

Individualised: AP & lateral neck XR, CXR, Endoscopy, CT, MRI/MRA

Commonest cause of stridor in infant — 80%

Clinical assessment: Good history → PE (stridor characteristics, insucking, respiratory distress) → Growth charts (body weight maintained along or increasing percentile) → duration of each milk intake, choking ^[1]

Management: Monitor with regular follow-up by Paediatrician or ENT. Severe cases may need supraglottoplasty under GA ^[1]

Why supraglottoplasty works: In laryngomalacia, the supraglottic tissues (omega-shaped epiglottis, short aryepiglottic folds, redundant arytenoid mucosa) prolapse into the airway during inspiration. Supraglottoplasty/aryepiglottoplasty trims this redundant tissue to widen the supraglottic inlet.

Subglottic diameter < 4 mm in full-term infant; < 3.5 mm in preterm

Grading — Cotton-Myers Classification ^[1]:

How it's graded: During LTB, the subglottis is sized with endotracheal tubes — the largest tube with air leak at 25 cmH₂O determines the functional diameter ^[1].

Treatment ^[1]:

CO₂ laser opening, Balloon dilatation, Tracheostomy, Laryngotracheal reconstruction (LTR) with intercostal cartilage augmentation

Treatment ^[1]:

• Treat underlying cause
• Conservative management
• Bilateral: 50% need tracheostomy
• Congenital palsy may recover at 2-5 years old
• Definitive surgery after adolescence: lateralisation or arytenoidectomy

Why Arnold-Chiari malformation? The vagus nerve nuclei in the medulla are compressed by cerebellar tonsillar herniation → bilateral recurrent laryngeal nerve dysfunction.

Symptomatic by 3 months. Inspiratory to biphasic stridor. Recurrent croup. 50% cutaneous haemangioma.

Treatment ^[1]:

Systemic steroid, Oral propranolol (beta-blocker), CO₂ laser ablation in selected cases, Tracheostomy for obstructing circumferential haemangioma

Why propranolol? Beta-blockers cause vasoconstriction (blocking β₂-mediated vasodilatation), inhibit VEGF/bFGF expression, and promote apoptosis of haemangioma endothelial cells. This is now first-line medical therapy.

Stridor in neonate, respiratory distress, choking, aspiration, difficult intubation. GA for excision.

Congenital midline defect of the posterior larynx, trachea, and anterior wall of oesophagus due to incomplete formation of tracheoesophageal septum.

• Benjamin-Inglis Classification (Type I–IV; Type IV has high mortality)
• Presents as stridor, aspiration on feeding
• Treatment depends on grading: conservative → endoscopic repair → open surgery

• Teratomas

60% present at birth. 75% in head & neck region. Macrocystic or microcystic. Can cause airway obstruction.

Treatment: Surgical excision; Injection with OK432 (an attenuated strain of Streptococcus pyogenes) ^[1]

Why OK432? It acts as a sclerosant, inducing an intense inflammatory reaction within the cyst wall, leading to fibrosis and shrinkage. Works best for macrocystic lesions.

1:8000 live births. F:M = 2:1. Failure of breakdown of buccopharyngeal membrane. Unilateral:Bilateral = 3:2. Bilateral is an ENT emergency because neonates are obligate nasal breathers. Treatment: Transnasal opening of atresia.

Pierre Robin syndrome, Treacher Collins syndrome, Apert syndrome, Crouzon syndrome — causing hypoplastic mandible, hypoplastic maxilla, retrognathia, choanal atresia

• Mandibular distraction may be used to advance the mandible and relieve airway obstruction ^[1]

Vascular ring (double aortic arch), Aberrant subclavian artery, Aberrant pulmonary artery — all cause extrinsic compression of trachea. Managed by CTSU (Cardiothoracic Surgical Unit).

6 months to 3 years, peak at 2 years. Caused by Parainfluenza virus, Influenza virus type A, RSV, Mycoplasma pneumoniae.

Management ^[1]:

5-10% may need admission. Systemic steroid. Nebulised adrenaline. Intubation for severe cases.

Recurrent croup needs to rule out underlying subglottic stenosis ^[1]

ENT & Paediatric emergency. 2-6 years old, peak 3-4 years. Caused by Haemophilus influenzae type B, β-haemolytic Streptococcus, Pneumococcus, Staphylococcus.

Management ^[1]:

Keep calm. No attempt for throat exam, blood taking or IV access [in the ward]. Diagnosis by history. Consult senior, senior paediatrician, ENT, anaesthetist. Bring patient to operation theatre. Gaseous induction followed by intubation. Blood culture, set up IV line [AFTER intubation]. Antibiotics: 3rd generation Cephalosporin.

Croup vs. Epiglottitis — Key Discriminators:

^[1][3]

Commonest deep neck infection in children < 4 years. Infected retropharyngeal lymph nodes.

Management: Watch out for airway. Transoral drainage and antibiotics. ^[1]

HPV 6, 11. Mother infected with genital warts → transmitted during delivery. Mean age of presentation 2 years. Papillomas can occur from lips to lungs. Presents with hoarseness, stridor.

Treatment ^[1]:

Excision with laryngeal debrider, CO₂ laser ablation, may need repeated sessions to prevent airway obstruction

Common between 1-3 years. Ask about choking episode, coughing spells, any witness.

Management: Rigid bronchoscopy (ventilating bronchoscope) under GA for removal ^[1]

Tumours (nasal cavity to larynx, thyroid), Infection (parapharyngeal abscess, peritonsillar abscess, Ludwig's angina, submandibular abscess), Bilateral vocal cord palsy, Trauma, Foreign body, Anaphylaxis, OSAS

Sore throat, Dyspnoea, Dysphagia, Hoarseness, Blood in saliva, Nasal symptoms, Smoking, Drinking, Fever, Neck swelling/pain

Vital signs, Fever, Head & neck exam, Oral cavity, Thyroid, Neck lymph nodes

XR neck, CXR, Laryngoscopy, Urgent CT neck ± oral cavity or thorax with contrast

Collection of pus between tonsillar capsule and superior constrictor. Sore throat, Dysphagia, Odynophagia, Airway obstruction, Peritonsillar swelling, Deviation of uvula to the other side, Trismus.

Management: Transoral incision and drainage, antibiotics ^[1]

Parapharyngeal abscess, retropharyngeal abscess. Causes: tonsillitis, dental origin. Neck swelling, sore throat, odynophagia, trismus, airway obstruction, stridor.

Management: Urgent consult ENT, watch out for airway obstruction, Laryngoscopy, Urgent CT neck with contrast, Transcervical drainage ± tracheostomy, Antibiotics, Consult dental for assessment. ^[1]

Infection of floor of mouth, submental and submandibular space. Septic. Hot-potato voice, dysphagia. Tender swelling at submental. Superior, posterior displacement of tongue → airway obstruction. Trismus.

Management: Urgent consult ENT, Laryngoscopy, CT oral cavity and neck with contrast, Transcervical drainage ± tracheostomy ^[1]

Why is Ludwig's angina so dangerous? The infection spreads through the fascial planes of the floor of mouth, pushing the tongue posterosuperiorly into the airway. Unlike quinsy, the pus is diffuse (cellulitis/phlegmon), making drainage more challenging, and airway compromise is rapid.

Can occur in adults. Sore throat, rapid onset, dysphagia. PE: painful over central neck. Watch out for airway obstruction. Consult ENT → laryngoscopy ± intubation or tracheostomy. Severe cases may be done in operation theatre. IV Augmentin.

Obstruction due to CA oropharynx, tongue, larynx, hypopharynx, thyroid. Bilateral vocal cord palsy in advanced CA oesophagus, thyroid. NPC.

• Blunt or penetrating neck injury → laryngeal fracture, haematoma, oedema → airway compromise
• Requires urgent ENT assessment, may need emergency tracheostomy

Difficulty in breathing, stridor. Causes include tumours, iatrogenic cause, stroke. Consult ENT, Laryngoscopy, Emergency tracheostomy.

Why bilateral VCP causes airway obstruction: Both cords sit in the paramedian position (adducted), leaving only a narrow slit for airflow. Unilateral palsy usually causes hoarseness without significant airway compromise because one cord can still abduct. ^[4][5]

1. Upper airway obstruction 2. For assisted ventilation 3. Prolonged intubation 4. Bronchial toilet

These align with the anaesthesia/surgery framework ^[4][5]:

• Bypass UAO (intrinsic tumour/foreign body, extrinsic compression, post-op oedema)
• Prolonged mechanical ventilation (avoid complications of prolonged ETT — laryngeal injury, patient discomfort)
• Facilitate weaning from ventilation
• Suctioning of secretions (bronchial toilet)

GA or LA (if failed intubation). Dissection down to trachea. Incision between 2nd and 3rd tracheal ring. Insertion of tracheostomy tube.

Why between 2nd and 3rd ring? Too high (1st ring/cricothyroid membrane area) risks subglottic stenosis and damage to the cricoid cartilage. Too low risks injury to the innominate artery and increases the risk of tracheo-innominate fistula. The 2nd-3rd interspace is the sweet spot for access while minimising complications.

CXR to rule out pneumothorax. Check tube tip position — 1-2 cm above carina for infants.

1. Immediate post-op — CXR to rule out pneumothorax 2. Emergency preparation in case of early dislodgement in ward 3. Frequent suction to prevent blockage, check patency and position of tube and tapes 4. Daily dressing 5. Change of tube — first change at 5-7 days, then depending on tube type and risk of blockage 6. Assess and decide on feeding mode for the patient 7. Long-term: home care plan, types of tube, equipment (suction machine, ventilator), speaking valve 8. Short-term: ENT assessment and time for decannulation

One-way valve allows free airflow into lungs. Valve closed on exhalation → directs expired air up the larynx and out through mouth/nose for phonation. Assess duration of use as tolerated, saturation monitoring, may need ST (speech therapy) assessment and training, increase use gradually especially in children.

Prerequisite for speaking valve use: There must be some air leak around the tracheostomy tube (i.e., cuff must be deflated or tube must be uncuffed). If the cuff is inflated, expired air cannot pass upward through the larynx and the patient will suffocate.

If a patient presents with UAO:

1. Assess ABCDE
2. Basic airway manoeuvres: Head-tilt chin-lift (if no C-spine concern), Jaw thrust (if C-spine concern)
3. Airway adjuncts: OPA (unconscious only — triggers gag in conscious), NPA (semi-conscious; C/I if basal skull fracture)
4. Ventilation: BVM with reservoir + high-flow O₂
5. Advanced: ETT intubation (gold standard definitive airway)
6. Surgical airway: Needle cricothyrotomy (emergency, last resort, ~30 min max) → Tracheostomy (definitive)

Post-thyroidectomy bilateral RLN injury → bilateral VCP → dyspnoea + stridor upon extubation → require immediate re-intubation ± tracheostomy. Post-thyroidectomy haematoma → venous obstruction → acute laryngeal oedema → airway compromise — management: cut subcuticular stitches and strap muscle stitches to evacuate haematoma. A surgical drain post-thyroidectomy serves to prevent airway obstruction by releasing pressure caused by wound swelling (as tested in 2025 MCQ Q53).

Stem: "A mother brought in her 3-year-old child because of difficulty in breathing. On assessment, you heard loud, high-pitched sounds when the child breathed in. What is the MOST IMMEDIATE concern?"

A. Asthma attack B. Severe infection C. Shock D. Upper airway obstruction ✓

Rationale: Loud high-pitched sounds on inspiration = inspiratory stridor = upper airway obstruction. Asthma presents with expiratory wheeze. Infection may be the underlying cause but the immediate concern is the obstructed airway. Shock doesn't present with inspiratory stridor.

Stem: "You are a first-year surgical resident. An 80-year-old lady, Ms. Lai, was admitted to the surgical ward today for enlarging neck swelling and increasing difficulty in breathing in the past 6 months."

Q1: "List six important questions that should be asked during history taking." (12 marks)

Q2: "List six important physical signs that should be checked." (12 marks)

Model answer for Q1: (1) Duration and rate of growth of the swelling (2) Dysphagia/odynophagia (3) Hoarseness/voice change (4) Stridor or noisy breathing (5) History of previous thyroid/neck surgery or radiation (6) Smoking and drinking history — The history mirrors the adult UAO history framework from this lecture ^[1]

Model answer for Q2: (1) Vital signs including SpO₂ (2) Stridor — phase and severity (3) Signs of respiratory distress (suprasternal/subcostal insucking, accessory muscle use) (4) Neck swelling — size, consistency, mobility with swallowing/tongue protrusion (5) Oral cavity examination (6) Cervical lymphadenopathy ^[1]

Stem: Patient with decreased consciousness and noisy breathing over his throat, SpO₂ 85%, septic shock picture.

Q11: "List three simple airway maneuvers to manage his airway." (9 marks)

Answer: (1) Head-tilt chin-lift (2) Jaw thrust (3) Suction of oropharynx / clearance of airway ^[4][6]

Q12: "Name the MOST APPROPRIATE simple airway adjunct to help manage his airway." (3 marks)

Answer: Oropharyngeal airway (OPA) — patient is unconscious, so OPA is appropriate (NPA would also be acceptable but OPA is preferred for unconscious patients needing prolonged BVM). ^[4][6]

Stem: "A 70-year-old man presented with shortness of breath. Wheezing during inspiration." Most likely diagnosis?

Options: A. Bronchiectasis, B. Cardiomyopathy, C. COPD, D. IPF, E. Lung abscess, F. Lung cancer with LUL obstruction, G. Malignant pleural effusion, H. Pneumococcal pneumonia, I. PE, J. Retrosternal goitre ✓

Rationale: Inspiratory wheeze (fixed extrathoracic obstruction) = retrosternal goitre compressing the trachea. Expiratory wheeze would suggest intrathoracic obstruction (COPD/asthma). This directly tests the concept of stridor/wheeze phase localising the obstruction level ^[1].

Stem: "A woman had known hyperthyroidism and large multinodular goitre, and she had total thyroidectomy done. A suction drain is inserted post-operatively. What is the purpose of keeping a surgical drain for this woman?"

A. To prevent surgical site infection by delivering antibiotics B. To prevent airway obstruction by releasing pressure caused by wound swelling — This is one acceptable answer, but the more standard answer is: C. To monitor post-operative thyroxine level directly D. To reduce haematoma formation by draining blood and serous fluid ✓

Rationale: The primary purpose of a surgical drain post-thyroidectomy is to drain blood/serous fluid and prevent haematoma accumulation. A post-thyroidectomy haematoma can cause venous congestion → laryngeal oedema → airway obstruction. Option B describes a downstream benefit but D is the most direct answer about the drain's purpose. Option A and C are incorrect.

Stem: "A 30-year-old man presents with recurrent angioedema without wheals, with a history of ICU admission for airway obstruction. His father as well as 2 of his 4 siblings also had a similar history. Which investigation is MOST APPROPRIATE?"

A. Tryptase B. C1-esterase inhibitor level ✓ C. Specific IgE panel D. Next generation sequencing

Rationale: Family history of angioedema + airway obstruction without wheals = hereditary angioedema (HAE) from C1-esterase inhibitor deficiency. This is autosomal dominant. Relevant to UAO because HAE can cause life-threatening laryngeal oedema.