Sleep Disorders and Their Physiological Effects

Sleep Requirements and Importance

• Average adult needs 7-9 hours of sleep daily to ensure:
  • Physical and mental restoration.
  • Long-term health and quality of life.
  • Sleep disorders can exacerbate pre-existing conditions.

Normal Stages of Sleep

• Sleep is an active process with specific brain regions being stimulated.
• Two primary sleep stages:
  • Non-Rapid Eye Movement (NREM)
  • Rapid Eye Movement (REM)
• NREM and REM cycle every 90-120 minutes, resulting in 4-5 cycles per night.

Non-Rapid Eye Movement Sleep (NREM)

• General Characteristics:
  • Occurs at the beginning of sleep.
  • EEG shows diminishing brain activity, indicating a restorative state.

Stages of NREM

• N1 (Light Sleep):
  • Characterized by slow rolling eye movements, low amplitude.
  • Comprises 5-10% of total sleep (a few minutes).
• N2 (Moderate Sleep):
  • EEG displays K complexes and sleep spindles.
  • Adults spend 40-50% of their sleep here.
• N3 (Deep Sleep):
  • Deepest sleep stage, 25% of total sleep.
  • Features slow wave or delta wave sleep with high amplitude.
  • Sensitivity to stimuli decreases, making it hard to wake.
  • Release of essential growth hormones, particularly in children/adolescents during the first half of the night.

Rapid Eye Movement (REM) Sleep

• High brain activity characterized by:
  • Eye rolling/rapid fluttering of eyes.
  • 25% of total sleep; dream activity occurs here.
  • EEG shows low-amplitude, mixed frequency waves.
  • Decreased muscle tone resembling a paralyzed state.

Physiological Effects of REM

• Decreased ventilatory response:
  • $P_{aO2}$ decreases by 2-12 mmHg.
  • $P_{aCO2}$ rises by 2-8 mmHg.
• Altered cardiovascular responses: blood pressure and heart rate changes.
• More profound effects in patients with existing pulmonary/cardiac diseases.

Sleep Disorders Overview

• Common disorders include:
  • Sleep-Related Breathing Disorders (SBD)
  • Insomnia (difficulty staying asleep)
  • Hypersomnia Disorder (e.g., sleepwalking)
  • Circadian Rhythm Disorders
  • Parasomnias (e.g., night terrors)
  • Sleep-Related Movement Disorders (e.g., restless leg syndrome)

Consequences of Excessive Daytime Sleepiness/Somnolence (EDS)

• Key symptom of sleep-related disorders.
• Impairs daily functioning, increases accident risk, impacts productivity and quality of life.

Sleep Apnea Types

• Obstructive Sleep Apnea (OSA): Most common, characterized by:
  • Apneas requiring a ≥90% airflow reduction for at least 10 seconds despite respiratory effort.
• Central Sleep Apnea: Less common, represents 10-15% of cases.
• Mixed Sleep Apnea: Combination of central and obstructive.

OSA Characteristics

• Occurs in 2-4% of adults, primarily caused by airway obstruction due to:
  • Obesity
  • Pharyngeal/neck adipose tissue
  • Anatomical features (e.g., tonsillar hypertrophy in rare cases).

Adult Risk Factors for OSA

• BMI >25
• Alcohol consumption before bedtime
• Smoking
• Nasal congestion
• Neck size (>17 inches for men, >16 inches for women)
• Males over 40 years old.

Hypopnea

• Defined as a significant decrease in breathing without complete airflow cessation:
  • A decrease in airflow by 30% with at least a 3% O2 desaturation for 10 seconds.

OSA in Children and Infants

• Main symptom is snoring.
• Caused by anatomical features of the airway.

Symptoms of Pediatric OSA

• OSA symptoms include:
  • Daytime sleepiness or hyperactivity.
  • Bedwetting after achieving bowel control.
  • Social withdrawal and poor academic performance.
  • Aggression.

Clinical Features for OSA

• Hypertension history
• Chronic nasal congestion
• Snoring (primary hallmark)
• Morning headaches, memory issues
• Symptoms of depression and nocturnal choking.

Screening Questionnaires

• Berlin Questionnaire:
  • 10-item survey assessing snoring, daytime sleepiness, BMI, and blood pressure.
• STOP-BANG Assessment:
  • 8 questions focusing on snoring, EDS, and risk factors for OSA.

Scoring for STOP-BANG

• 1 point for each positive response; scoring results:
  • <3 = low probability of OSA
  • >3 = high probability of OSA
  • >5 = high probability of moderate to severe OSA.

Sleep Study (Polysomnography)

• Overnight PSG is the gold standard for diagnosing sleep disorders.
• Records:
  • EEG for sleep stages
  • EOG for REM periods
  • EMG for muscle tone
  • Airflow measurements
  • Oxygen saturation (SpO2)
  • Snoring level.

Apnea-Hypopnea Index (AHI)

• Number of apneas and hypopneas per hour of sleep:
  • AHI <5: Normal
  • AHI 5–15: Mild sleep apnea (treatment depending on symptoms).
  • AHI 15-30: Moderate sleep apnea.
  • AHI >30: Severe sleep apnea (requires treatment).

Treatment Goals and Strategies

• Normalize SaO2, ventilation.
• Eliminate apneic events and improve sleep quality.

Treatment Options:

• Behavioral: Improve sleep hygiene and consider lifestyle changes like weight loss, avoidance of alcohol, and positional therapy.
• Medical:
  • Continuous Positive Airway Pressure therapy (CPAP) is the first-line treatment for OSA.
  • Auto CPAP (APAP) allows for automatic adjustment of pressure.
• Surgical Options:
  • Inspire Stimulator for non-CPAP tolerant patients.
  • Uvulopalatopharyngoplasty (UPPP) and maxillofacial surgery (less common and have lower success rates).

Central Sleep Apnea (CSA)

• Lack of respiratory effort leading to apnea caused by central factors (e.g., brainstem injury, narcotic overdose).

Hypoventilation Syndrome

• Reduced breathing size at night due to conditions like obesity or neuromuscular diseases.
• Treatment often involves BiPAP or nocturnal noninvasive ventilation.

Obesity Hypoventilation Syndrome

• Characterized by daytime hypercapnia in obese individuals.
• Treatment includes noninvasive ventilation and bilevel positive airway pressure therapy (BiPAP).

Full Face Masks in Therapy

• Essential for any connected mask system to allow exhalation through vented masks and exhalation ports to enable patient comfort during therapy.