Sleep Disordered Breathing: Diagnosis and Treatment

Sleep Disordered Breathing (SDB)

Definition and Overview

Sleep disordered breathing (SDB) refers to a group of disorders characterized by abnormal respiratory patterns or insufficient ventilation during sleep. The most common forms include obstructive sleep apnea (OSA) and central sleep apnea (CSA).

• Abnormal respiratory patterns: Includes the presence of apneas (complete cessation of airflow) or hypopneas (partial reduction in airflow).

• Insufficient ventilation: Inadequate air exchange during sleep, leading to decreased oxygenation.

Apnea: A period when a patient stops breathing for 10 seconds or more, often resulting in brief arousal to resume breathing.

Hypopnea: A period when breathing becomes abnormally shallow (at least a 30% decrease in airflow) for 10 seconds or more, usually with oxygen desaturation or arousal.

Clinical significance: SDB disrupts sleep architecture, causes excessive strain on the nervous and cardiovascular systems, and may lead to daytime fatigue and other health complications.

Sleep Studies

Purpose and Methods

Sleep studies are diagnostic tests used to monitor a patient's breathing, body movements, and physiological responses during sleep to identify sleep disorders such as sleep apnea.

• Polysomnography (PSG): The gold standard for diagnosing SDB, typically performed in a clinic, hospital, or sleep lab.

• Home Sleep Studies: Portable monitoring devices allow for sleep studies to be conducted at home, increasing patient comfort and convenience.

Parameters Monitored

• Airflow (nasal and oral)

• Blood oxygen saturation (SpO2)

• Respiratory effort (chest and abdominal movements)

• Electroencephalogram (EEG) for sleep stages

• Electrocardiogram (ECG) for heart rhythm

• Body position and limb movements

Sleep Study Measurements

The severity of SDB is classified using the apnea/hypopnea index (AHI), which represents the number of apneas and hypopneas per hour of sleep.

Severity	AHI (per hour)
Normal	<5
Mild	5 – 15
Moderate	15 – 30
Severe	>30

Example: A patient with an AHI of 20 would be classified as having moderate sleep apnea.

Sleep Apnea Treatment Options

Positive Airway Pressure (PAP) Therapy

PAP therapy is the most effective treatment for OSA and certain types of CSA. It works by delivering pressurized air through a mask, creating a pneumatic splint that prevents upper airway collapse.

• Continuous Positive Airway Pressure (CPAP): Delivers air at a fixed pressure throughout the night.

• Automatic Positive Airway Pressure (APAP): Adjusts pressure automatically based on detected airway resistance.

• Bilevel Positive Airway Pressure (BiPAP): Provides higher pressure during inhalation and lower pressure during exhalation, useful for patients with higher pressure needs or those intolerant to CPAP.

Result: PAP therapy can restore normal sleep patterns and resolve sleep debt in patients with severe sleep apnea.

Relevant Equations

• Apnea-Hypopnea Index (AHI): $\text{AHI} = \frac{\text{Number of apneas + hypopneas}}{\text{Total sleep time in hours}}$

Oral Appliance Therapy

Mandibular repositioning devices (MRDs) are custom-made oral appliances that hold the lower jaw forward during sleep, increasing airway space and reducing collapse.

• Indicated for mild to moderate OSA or for patients who cannot tolerate PAP therapy.

• Not suitable for all patients; effectiveness varies.

Alternative Treatment Options

• Surgery: Considered when other treatments fail or are not tolerated. Includes:

  • Uvulopalatopharyngoplasty (UPPP): Removal of excess tissue in the throat to widen the airway.

  • Tracheostomy: Creation of a direct airway through the neck, reserved for severe, life-threatening cases.

Risks: All surgical options carry inherent risks and variable success rates.

Summary Table: Sleep Apnea Treatment Modalities

Treatment	Mechanism	Indication
CPAP	Fixed positive airway pressure	All severities, especially moderate-severe OSA
APAP	Auto-adjusting airway pressure	Variable pressure needs, REM-related OSA
BiPAP	Higher inspiratory, lower expiratory pressure	CPAP intolerance, central sleep apnea
Oral Appliance	Mandibular advancement	Mild-moderate OSA, CPAP intolerance
UPPP Surgery	Airway tissue removal	CPAP/oral appliance failure
Tracheostomy	Direct airway creation	Severe, refractory cases

Additional info: SDB is closely linked to cardiovascular, metabolic, and neurocognitive complications. Early diagnosis and appropriate treatment are essential for improving patient outcomes.