Unit
- Obstructive sleep apnea (OSA): A disorder characterized by repeated collapse of the upper airway during sleep, leading to apnea or hypopnea episodes that disrupt sleep architecture and cause intermittent hypoxia.
- Anatomical factors: Enlarged tonsils, retrognathia, obesity (increased pharyngeal fat deposition), and nasal obstruction all contribute to airway collapsibility by reducing the cross-sectional area of the pharynx.
- Neuromuscular control: During sleep, pharyngeal dilator muscles (e.g., genioglossus) lose tone. In OSA patients, this loss is more profound, allowing the airway to collapse even at normal negative inspiratory pressures.
- Diagnostic scoring: The apnea-hypopnea index (AHI) measures severity: mild (5-15 events/hour), moderate (15-30), severe (>30). Respiratory disturbance index (RDI) includes respiratory effort-related arousals.
- Consequences of untreated OSA: Systemic hypertension, cardiovascular disease (arrhythmias, heart failure, stroke), metabolic dysfunction (insulin resistance), daytime somnolence, cognitive impairment, and increased accident risk.
- Pathophysiology of CPAP effect: Positive airway pressure acts as a pneumatic splint, maintaining pharyngeal patency throughout the respiratory cycle. The effective pressure must exceed the critical closing pressure of the airway.
- Patient variability: Required pressure differs based on sleep stage (REM vs. NREM), body position (supine vs. lateral), and nasal patency. This variability underpins the rationale for auto-adjusting CPAP devices.
- Endotyping research: Four main pathophysiological traits (anatomy, muscle responsiveness, arousal threshold, loop gain) influence CPAP response. A high arousal threshold may paradoxically worsen central apneas if pressure is too high.
- Gender differences: Women often present with atypical symptoms (insomnia, fatigue) and less severe AHI. CPAP therapy may be underprescribed in women due to lower suspicion and different fat distribution patterns.
- Comorbidities impact: Conditions like chronic obstructive pulmonary disease (overlap syndrome), congestive heart failure (Cheyne-Stokes respiration), and opioid use can cause central or mixed apneas requiring differentiated therapy (e.g., adaptive servo-ventilation).
- Adherence challenges: Many patients struggle with CPAP adherence due to mask discomfort, claustrophobia, or noise. Up to 50% discontinue within the first year. Interventions include desensitization, heated humidification, and alternative mask interfaces. Regular follow-up improves long-term compliance.
- Pressure titration protocols: Manual titration in a sleep lab involves gradual pressure increases until apneas are eliminated. Auto-CPAP devices adjust pressure in real-time based on flow limitation, snoring, and apnea detection. In-home auto-titration is increasingly used for uncomplicated OSA.
- Mask selection factors: Nasal masks, full-face masks, and nasal pillows each have distinct advantages. Nasal pillows are minimal but require adequate nasal patency; full-face masks are useful for mouth breathers. Proper sizing and fit are critical to prevent leaks and maximize therapy effectiveness.
Scope of Practice
Role: CPAP Therapy Manager in a Sleep Clinic
Within scope:
- Reviewing sleep study reports to identify OSA diagnosis and severity
- Educating patients about OSA pathophysiology and CPAP mechanism
- Explaining the link between untreated apnea and chronic health conditions
- Recommending CPAP therapy based on physician prescription
- Documenting patient understanding in the medical record
Outside scope:
- Interpreting polysomnography raw data for diagnostic purposes
- Diagnosing sleep disorders beyond OSA
- Prescribing CPAP pressure settings without a physician order
- Modifying treatment for central sleep apnea without specialist input
- Providing medical clearance for CPAP therapy
Quick Revision
- Obstructive sleep apnea involves repeated airway collapse during sleep, leading to hypoxia and sleep disruption.
- CPAP therapy splints the airway open with positive pressure, preventing apnea events.
- AHI and RDI quantify severity; understanding patient variability improves treatment outcomes.
- Untreated OSA is linked to cardiovascular, metabolic, and cognitive complications.