In-Depth Notes on Sleep and Sleep-Related Breathing Disorders

Lecture Overview

  • Lecture 15: Sleep and Sleep-Related Breathing Disorders
  • Focus on the significance of sleep cycles, EEG patterns, and clinical cases of sleep disorders.

Sleep Overview

  • Sleep is a cyclic state of decreased motor activity and perception, essential for brain maturation and strengthening synaptic connections.
  • Divided into two main types: Slow Wave Sleep (SWS) and Rapid Eye Movement (REM) Sleep.
Electroencephalogram (EEG) Patterns
  • Alpha Waves (10 Hz): Occur during relaxed wakefulness with closed eyes; decrease with activity.
  • Beta Waves (14-30 Hz): Associated with alertness and mental activity.
  • Theta Waves (4-8 Hz): Occur during severe emotional stress; associated with drowsiness.
  • Delta Waves (< 4 Hz): Dominant in deep sleep; rare during wakefulness.
Stages of Sleep
  • Sleep progresses through various stages:
    • Stage 1: Light sleep, transition from wakefulness.
    • Stage 2: Sleep spindles appear, deeper relaxation.
    • Stage 3 & 4: Deep, slow-wave sleep, low frequency EEG.
    • REM Sleep: High brain activity, rapid eye movements, and muscle paralysis.
Slow Wave Sleep (SWS) vs. REM Sleep
  • SWS:
    • Characterized by low-frequency EEG waves.
    • Decreased muscle tone and overall brain activity.
    • Logical dreams occur.
  • REM Sleep:
    • High-frequency EEG waves, rapid eye movements, muscle paralysis (postural atonia).
    • Emotionally charged narratives in dreams.

Narcolepsy

  • A neurological disorder characterized by abnormal regulation of sleep/wake cycles.
  • Symptoms:
    • Sleep paralysis - paralysis occurring at sleep onset or awakening.
    • Hypnagogic hallucinations - vivid dream-like experiences at sleep onset.
  • Caused by a lack of orexin, a neuropeptide produced in the hypothalamus; autoimmune destruction of orexin-producing cells is implicated.

Sleep-Related Breathing Disorders

1. Obstructive Sleep Apnea (OSA)
  • Clinical Case: An obese, 37-year-old man with symptoms such as daytime sleepiness, hypertension, and snoring.
  • Characterized by:
    • Repeated drops in arterial O₂ levels during sleep.
    • Ineffective breathing movements, abnormally coordinated thoracic and abdominal movements.
  • Treatment: CPAP (Continuous Positive Airway Pressure) to keep airways open and maintain blood oxygen levels.
2. Partial Diaphragmatic Paralysis
  • Clinical Case: A 22-year-old woman with difficulty breathing during non-REM and REM sleep due to diaphragm paralysis (injury to phrenic nerve).
  • Blood O₂ saturation is normal during wakefulness but declines during sleep.
  • Treatment Options:
    • Inhibiting REM sleep or using artificial ventilation.
3. Chronic Bronchitis
  • Clinical Case: A 60-year-old man suffering from lung disease and daytime hypoxia.
  • Symptoms worsen during sleep, significantly affecting oxygen/CO₂ levels.
  • Treatment: Inhaled O₂ therapy while monitoring for CO₂ narcosis.
4. Ondine's Curse (Congenital Central Hypoventilation Syndrome)
  • A rare condition resulting in loss of autonomic breathing control during sleep, maintaining voluntary control.
  • Symptoms include cyanosis and cardiovascular impairment.
  • Diagnosis and Treatment: Monitoring ventilation and potentially using a phrenic pacemaker.
5. Inverse Ondine's Curse
  • A condition following brain injury leading to inability to initiate voluntary breathing, although automatic breathing remains intact.
  • Diagnosed with imaging studies and monitoring of breathing patterns.

Effects of Sleep Deprivation

  • Long-term effects include:
    • Irritability, cognitive impairment, memory issues, hallucinations, ADHD-like symptoms.
    • Physical effects: increased heart rate variability, tremors, risk of diabetes and heart disease, growth suppression, obesity, and decreased temperature regulation.

Summary of Important Concepts

  • Understanding sleep-related disorders is critical for medical practitioners given their prevalence and impact on quality of life.
  • Integration of sleep physiology in the medical curriculum is necessary, as a lack of sleep knowledge can contribute to inadequate treatment of common conditions.