Obstructive Sleep Apnea (OSA)

MS ENT Postgraduate Theory Answer - 20 Marks

1. Introduction and Historical Background

2. Epidemiology

• Affects approximately 2-4% of middle-aged adults; prevalence rises sharply with age and obesity
• Male:Female ratio = 2:1; postmenopausal women have similar prevalence to age-matched men
• Risk factors: obesity (BMI >30), male sex, age >50, large neck circumference (>43 cm males, >40 cm females), craniofacial abnormalities, family history, alcohol use, nasal obstruction
• Conditions with high OSA prevalence: hypertension (60%), coronary artery disease, stroke, type 2 diabetes, congestive heart failure, atrial fibrillation

3. Definitions and Classification

Respiratory Event Definitions (AASM):

Severity Classification (AASM - by AHI):

Important Indices:

• AHI (Apnea-Hypopnea Index): Number of apneas + hypopneas per hour of sleep
• RDI (Respiratory Disturbance Index): Apneas + hypopneas + RERAs per hour
• ODI (Oxygen Desaturation Index): Desaturation events per hour

Diagnostic Criteria (AASM/ICSD-3):

1. AHI ≥5 predominantly obstructive events per hour with associated symptoms or comorbidities, OR
2. AHI ≥15 predominantly obstructive events per hour regardless of symptoms

4. Pathophysiology

A. Impaired Upper Airway Anatomy

• Obesity, soft tissue hypertrophy, and craniofacial abnormalities (retrognathia, micrognathia) increase extraluminal tissue pressure around the pharynx
• At sleep onset, muscle tone decreases and the structurally compromised airway collapses
• Three sites of obstruction (Fujita Classification):
  • Type I: Retropalatal only
  • Type II: Both retropalatal and retrolingual
  • Type III: Retrolingual only

B. Low Arousal Threshold

• Some patients with OSA arouse from sleep at low levels of respiratory effort, preventing adequate recovery of airway patency and destabilizing sleep architecture

C. Inadequate Dilator Muscle Response

• Pharyngeal dilator muscles (genioglossus, tensor veli palatini) fail to maintain patency during sleep due to impaired reflex pathways from CNS
• Loop gain: The complex reflex pathways from CNS to pharynx that control pharyngeal dilator muscles may fail to maintain pharyngeal patency even without anatomic abnormality

D. High Loop Gain (Unstable Respiratory Control)

• An oversensitive ventilatory control system responds excessively to perturbations, causing cyclical swings in ventilation that perpetuate obstruction

Pathophysiologic Cascade:

• Progressive hypoxia and hypercapnia
• Intrathoracic pressure swings (markedly negative)
• Sympathetic activation and cortisol release
• Arousal terminates the episode (often unconscious/microarousal)

5. Clinical Features

Nocturnal Symptoms:

• Loud snoring (most common presenting complaint from bed partners)
• Witnessed apneas, choking, gasping
• Restless sleep
• Nocturnal sweating
• Nocturia / nocturnal enuresis
• Sleep fragmentation, frequent awakenings

Daytime Symptoms:

• Excessive Daytime Somnolence (EDS) - hallmark symptom
• Morning headache, sore throat
• Fatigue, unrefreshed sleep
• Decreased concentration and memory
• Cognitive dysfunction
• Depression and personality changes
• Decreased libido and impotence

Physical Examination Findings:

6. Investigations

A. Polysomnography (PSG) - Gold Standard

• EEG (sleep staging)
• EMG (chin and limb electrodes)
• EOG (eye movements for REM identification)
• ECG
• Nasal airflow (thermistor + pressure transducer)
• Thoracoabdominal effort (respiratory belts)
• Pulse oximetry (SpO2)
• Body position
• Esophageal manometry (if RERA detection needed)

B. Home Sleep Apnea Test (HSAT)

• Portable device for uncomplicated OSA
• Records fewer channels (airflow, effort, SpO2, HR, position)
• Appropriate for high pre-test probability, absence of comorbidities
• May underestimate AHI (monitors time awake + asleep)
• Not suitable if: central apnea suspected, significant comorbidities, prior non-diagnostic HSAT

C. Screening Questionnaires:

• Snoring (loud)
• Tired (daytime fatigue)
• Observed apnea
• Pressure (hypertension)
• BMI >35
• Age >50
• Neck circumference >40 cm (F) / >43 cm (M)
• Gender (male)
• Score 5-8 = high probability of moderate-to-severe OSA

D. Additional Investigations:

• Drug-Induced Sleep Endoscopy (DISE): Dynamic evaluation of airway collapse under light sedation mimicking sleep - guides surgical planning. Uses VOTE classification (Velum, Oropharynx, Tongue base, Epiglottis) or NOHL classification
• Cephalometric radiograph: 2D bony and soft tissue assessment; OSA patients show inferior hyoid displacement, smaller posterior airway space, longer soft palates
• CT/MRI: 3D airway assessment
• Müller Maneuver: Awake nasopharyngoscopy with forced inhalation against closed glottis - predicts UPPP success
• Fiberoptic nasopharyngoscopy: Identifies site and degree of obstruction

7. Complications / Sequelae

Cardiovascular:

• Systemic hypertension (most common - OSA is an independent risk factor)
• Coronary artery disease and myocardial infarction
• Atrial fibrillation and arrhythmias
• Congestive heart failure
• Pulmonary hypertension
• Stroke (increased risk 2-4x)
• Sudden cardiac death (predominantly during sleep hours)

Metabolic:

• Type 2 diabetes mellitus (insulin resistance from intermittent hypoxia)
• Metabolic syndrome

Neuropsychiatric:

• Cognitive impairment, memory loss
• Depression and anxiety
• Increased motor vehicle accident risk (2-7x normal)

Other:

• Nocturia/enuresis (altered ANP secretion)
• Sexual dysfunction
• Increased perioperative risk (anesthetic complications)
• Pediatric OSA: failure to thrive, behavioral problems, neurocognitive deficits, enuresis, cor pulmonale

8. Management

A. Conservative/Lifestyle Measures (All Patients):

• Weight loss: Most effective; 10% weight loss reduces AHI by ~26%
• Positional therapy: Lateral sleep positioning for position-dependent OSA
• Avoidance of alcohol, sedatives, and hypnotics (worsen muscle hypotonia)
• Treating nasal congestion
• Sleep hygiene

B. Positive Airway Pressure (PAP) Therapy - First Line

• CPAP: Fixed pressure (most common, 4-20 cm H2O)
• APAP (Auto-CPAP): Automatically adjusts pressure based on airway resistance
• BiPAP (Bilevel PAP): Separate inspiratory and expiratory pressures - used for OHS, central apnea, CPAP intolerance

C. Oral Appliances (Mandibular Advancement Devices - MAD):

• Used in mild-moderate OSA or CPAP non-tolerant patients
• Advance mandible forward by 50-75%, increasing retropalatal and retrolingual space
• Less effective than CPAP but better compliance
• Contraindicated in severe periodontal disease, TMJ disorders

D. Surgical Management:

1. Nasal Surgery:

• Septoplasty, turbinoplasty, FESS
• Rarely definitive alone but improves CPAP tolerance and reduces CPAP pressure requirements

2. Palatal/Oropharyngeal Surgery:

• Tonsillectomy and adenoidectomy (T&A): First-line in pediatric OSA; curative in 70-80% of children; also beneficial in adults with large tonsils
• Uvulopalatopharyngoplasty (UPPP): Described by Fujita (1981); resection of redundant palatal/pharyngeal tissue with tonsillectomy
  • Success rate 50% overall in unselected patients (AHI <20, 50% improvement)
  • Friedman Staging predicts success:
    • Stage I (small tonsil-large palate+BMI<40): 80% success
    • Stage II: 40% success
    • Stage III: Only 8% success
  • Complications: Nasal reflux (12-15%), bleeding (1-5%), infection (2%), VPI
  • Modified UPPP (UPPP + pharyngoplasty) improves outcomes
• Expansion sphincter pharyngoplasty (ESP): Addresses lateral pharyngeal wall collapse better than UPPP
• Lateral pharyngoplasty: Improves retropalatal lateral dimension
• Radiofrequency ablation (somnoplasty): Office-based tissue reduction

3. Tongue Base / Hypopharyngeal Surgery:

• Lingual tonsillectomy: For lingual tonsillar hypertrophy (coblation or TORS)
• Tongue base radiofrequency ablation: Reduces tongue base volume
• Genioglossus advancement (GA): Advances genial tubercle with genioglossus attachment anteriorly, preventing tongue base prolapse
• Hyoid myotomy and suspension: Advances hyoid and tongue base anteriorly, opens retrolingual space

4. Hypoglossal Nerve Stimulation (Upper Airway Stimulation - Inspire device):

• Implantable neurostimulator sensing respiratory effort, stimulating hypoglossal nerve during inspiration to advance tongue/dilate pharynx
• FDA-approved for moderate-severe OSA, CPAP-intolerant patients with AHI 15-65, BMI <32, no complete concentric collapse at velum on DISE
• Significant recent evidence; mean AHI reduction of 68%

5. Skeletal/Maxillomandibular Surgery:

• Maxillomandibular Advancement (MMA): Considered gold standard surgical cure; advances maxilla and mandible 10-12 mm, dramatically enlarging entire upper airway
  • Success rate 75-100% (AHI <20 with ≥50% improvement)
  • Riley-Powell-Stanford Protocol: Sequential phases (nasal surgery → UPPP → MMA for failures)
  • Suitable for patients with craniofacial anomalies, retrognathia, failed soft tissue surgery

6. Tracheostomy:

• Bypasses entire upper airway obstruction; definitive and 100% effective
• Reserved for severe, life-threatening OSA unresponsive to all other treatments
• Also used perioperatively in morbidly obese patients undergoing sleep surgery

7. Pediatric-Specific Surgery:

• T&A is the primary surgical treatment
• Additional options: Supraglottoplasty (for laryngomalacia-associated OSA), midface advancement (syndromic craniofacial)

E. Multilevel/Combination Surgery:

• OSA frequently has multiple anatomical sites of obstruction
• DISE-guided multilevel surgery has better outcomes than single-level procedures
• Phase I (soft tissue): Nasal, palatal, tongue base procedures combined
• Phase II (skeletal): MMA for Phase I failures

9. Special Considerations

OSA in Children:

• Most common cause: Adenotonsillar hypertrophy
• Presentation: Nocturnal: snoring, restless sleep, enuresis; Daytime: hyperactivity (not EDS), behavioral/learning problems
• T&A is first-line; PSG criteria differ from adults (AHI ≥1 in children is abnormal)
• Complications: Failure to thrive, cor pulmonale, neurocognitive deficits

OSA and Anesthesia:

• High perioperative risk: difficult airway, increased sensitivity to opioids/sedatives, postoperative airway collapse
• Pre-op CPAP should be continued perioperatively; ASA guidelines recommend caution with opioids, monitoring in high-dependency unit

OSA and Pregnancy:

• Gestational hypertension, preeclampsia, and fetal growth restriction risk increased

10. Summary / Key Points

• Cummings Otolaryngology Head and Neck Surgery (7th ed.) - Chapter 15: Sleep-Disordered Breathing
• Scott-Brown's Otorhinolaryngology Head & Neck Surgery
• AASM (American Academy of Sleep Medicine) - International Classification of Sleep Disorders (ICSD-3)
• Murray & Nadel's Textbook of Respiratory Medicine
• Braunwald's Heart Disease (Sleep-Disordered Breathing chapter)