Obstructive Sleep Apnea

What is obstructive sleep apnea (OSA)?

Recurrent episodes of upper airway obstruction during sleep causing apneas, hypopneas, or respiratory‑effort related arousals (RERAs).

What is an apnea?

A ≥10‑second cessation of airflow with continued respiratory effort.

What is a hypopnea?

A ≥30% reduction in airflow for ≥10 seconds with ≥3% oxygen desaturation or arousal.

What causes airway collapse in OSA?

Loss of pharyngeal dilator muscle tone during sleep leading to upper airway narrowing and obstruction.

How common is OSA in adults?

Approximately 10–30% of adults, higher in older and obese populations.

Which sex is more affected by OSA?

More common in males, but post‑menopausal females have increased risk.

How does age affect OSA prevalence?

Risk increases with age due to decreased airway tone and increased comorbidities.

What are major risk factors for OSA?

• Obesity

• Male sex

• Age >50

• Large neck circumference

• Craniofacial abnormalities

• Family history

• Hypothyroidism

• Nasal obstruction

• Alcohol/sedative use

• Smoking

Which risk factor is the strongest modifiable predictor of OSA?

Obesity.

How does hypothyroidism contribute to OSA risk?

Causes macroglossia, myxedema, and decreased ventilatory drive, all of which worsen airway obstruction.

How does alcohol increase OSA severity?

Alcohol reduces upper airway muscle tone and increases collapsibility during sleep.

What is the core pathophysiology of OSA?

Repetitive upper airway collapse → intermittent hypoxia → sympathetic activation → sleep fragmentation → cardiometabolic stress.

What is the consequence of intermittent hypoxia in OSA?

Increased oxidative stress, inflammation, and sympathetic overactivity contributing to hypertension and cardiovascular disease.

What symptoms are commonly associated with OSA?

• Daytime sleepiness

• Loud snoring

• Witnessed apneas

• Non‑restorative sleep

• Morning headaches

• Nocturia

• Irritability

• Cognitive impairment

What is excessive daytime sleepiness?

Inability to stay awake during passive activities due to chronic sleep fragmentation.

What physical exam findings may suggest OSA?

• Elevated BMI

• Large neck circumference

• Crowded oropharynx (Mallampati III–IV)

• Nasal obstruction

• Signs of hypertension

What labs are commonly ordered when evaluating fatigue possibly due to OSA?

• CBC

• TSH and free T4

• CMP

Why is a CBC ordered in suspected OSA?

To rule out anemia as a cause of fatigue.

Why is TSH ordered in suspected OSA?

Hypothyroidism can mimic or worsen OSA symptoms.

What is the gold standard diagnostic test for OSA?

Polysomnography (in‑lab sleep study).

What does polysomnography measure?

• Airflow

• respiratory effort

• oxygen saturation

• EEG, EMG, EKG

• sleep stages

• limb movements.

What is home sleep apnea testing (HSAT)?

A simplified at‑home test measuring airflow, respiratory effort, and oxygen saturation

What is the apnea‑hypopnea index (AHI)?

Number of apneas + hypopneas per hour of sleep.

What AHI defines mild OSA?

AHI 5–14.

What AHI defines moderate OSA?

AHI 15–29.

What AHI defines severe OSA?

AHI ≥30.

What symptoms + AHI combination can diagnose OSA?

AHI ≥5 with symptoms (daytime sleepiness, snoring, witnessed apneas).

Is imaging routinely used in OSA diagnosis?

No, imaging is not routinely required unless evaluating craniofacial abnormalities or surgical planning.

What are the primary treatment goals for OSA?

Reduce apneas/hypopneas, improve daytime functioning, improve sleep quality, and reduce cardiovascular risk.

What is first‑line therapy for moderate–severe OSA?

CPAP (continuous positive airway pressure).

How does CPAP work?

Provides constant pressure to splint the upper airway open during sleep.

What is APAP?

Auto‑titrating positive airway pressure that adjusts pressure based on detected events.

What is BPAP?

Bilevel positive airway pressure providing separate inspiratory and expiratory pressures

What are common side effects of CPAP therapy?

Nasal dryness, congestion, mask discomfort, aerophagia.

What strategies improve CPAP adherence?

Humidification, mask refitting, gradual acclimation, patient education.

What lifestyle modifications help treat OSA?

• Weight loss

• Avoid alcohol/sedatives

• Positional therapy

• Treat nasal obstruction

• Improve sleep hygiene

How much weight loss can improve OSA severity?

Even 10% weight loss can significantly reduce AHI.

What oral appliances can be used for OSA?

Mandibular advancement devices that reposition the jaw to enlarge the airway.

What surgical options exist for OSA?

• UPPP (uvulopalatopharyngoplasty)

• Maxillomandibular advancement

• Hypoglossal nerve stimulation (Inspire)

Is there a primary pharmacologic treatment for OSA?

No, medications do not treat airway obstruction.

When are wake‑promoting agents used in OSA?

For residual daytime sleepiness after optimal PAP therapy (e.g., modafinil, solriamfetol).

What cardiovascular complications are associated with untreated OSA?

• Hypertension

• Arrhythmias (AFib)

• MI

• Stroke

• Heart failure

• Pulmonary hypertension

What metabolic complications are associated with OSA?

• Insulin resistance

• Type 2 diabetes

• Dyslipidemia

• Weight gain

What neurocognitive complications are associated with OSA?

• Memory impairment

• Poor concentration

• Mood disorders

• Increased motor vehicle accidents

How is OSA monitored after diagnosis?

PAP adherence monitoring, symptom review, equipment checks, and repeat sleep study if symptoms persist.

When should a repeat sleep study be considered?

PAP intolerance, persistent symptoms, major weight change, or surgical evaluation.

What prevention strategies reduce OSA risk?

• Weight control

• Avoid alcohol/sedatives

• Treat nasal obstruction

• Manage endocrine disorders

What conditions are included in the differential diagnosis for fatigue similar to OSA?

• Hypothyroidism

• Anemia

• B12 deficiency

• CHF

• Narcolepsy

• RLS

• Anxiety/depression

• Circadian rhythm disorders

• Malignancy

• Substance effects (ETOH, caffeine, nicotine)

What is a key clinical pearl regarding obesity and OSA?

Obesity is the strongest modifiable risk factor for OSA.

What AHI value is considered severe and highly testable?

AHI ≥30

What is the first‑line therapy for moderate–severe OSA?

CPAP.

What endocrine disorder can mimic or worsen OSA?

Hypothyroidism.

What is a classic symptom triad for OSA?

• Snoring

• Witnessed apneas

• Daytime sleepiness

What is a major reason to treat OSA aggressively?

It significantly reduces cardiovascular morbidity and mortality.