Chart — Sleep Medicine
Obstructive vs Central Sleep Apnea
OSA and CSA both fragment sleep with recurrent apneas, but their mechanisms — and therefore their treatments — are fundamentally different. This chart maps the key distinguishing features side by side so you can orient quickly, whether you are reviewing a polysomnography report or preparing for boards.
Written by Apex Respiratory Editorial Team
Educational use only. This material supports respiratory therapy education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional protocols, or physician orders. Always follow facility policies and current provider orders, and verify calculations independently before clinical use.
Overview
Sleep-disordered breathing encompasses a spectrum of conditions characterized by repeated pauses in airflow during sleep. The two most clinically important categories are obstructive sleep apnea (OSA) — caused by physical collapse of the upper airway despite ongoing drive to breathe — and central sleep apnea (CSA), in which the brain temporarily fails to send the signal to breathe at all. Both produce oxygen desaturation and arousal, but the polysomnographic signatures, patient populations, and therapeutic strategies differ substantially. Correctly distinguishing them is essential before initiating positive-pressure therapy, because the wrong device can worsen outcomes (see Key Pitfall row).
OSA vs CSA: Feature Comparison
| Feature | Obstructive (OSA) | Central (CSA) |
|---|---|---|
| Mechanism | Upper airway collapses despite preserved respiratory drive | Absent or reduced central respiratory drive |
| Respiratory effort during event | PRESENT (paradoxical chest/abdominal motion) | ABSENT |
| Airflow during event | Absent or reduced | Absent or reduced |
| Snoring | Loud, habitual | Usually absent |
| Typical body habitus | Often obese | Variable; heart failure / opioid / neurologic |
| Common causes | Obesity, crowded/narrow airway, retrognathia, enlarged tonsils | Heart failure (Cheyne-Stokes), stroke, chronic opioids, high altitude, brainstem lesions |
| Daytime ABG / CO₂ | Usually normal (high only with OHS overlap) | Normal or high (in hypercapnic forms) |
| Breathing-pattern clue | Repetitive obstruction ending in an arousal | Crescendo-decrescendo (Cheyne-Stokes) pattern |
| First-line therapy | CPAP | Treat the underlying cause; CPAP for coexisting OSA; ASV (NOT in HFrEF EF ≤ 45%); bilevel-ST for hypercapnic forms |
| Key pitfall | Mask leak leading to nonadherence | ASV is harmful in symptomatic HFrEF (SERVE-HF trial) |
How to Tell Them Apart
The single most reliable discriminator on a polysomnography (PSG) report is the respiratory-effort channel— typically recorded with respiratory inductance plethysmography (RIP) belts around the chest and abdomen. When effort signals are present during an apnea (even paradoxical, out-of-phase motion), the event is obstructive. When the effort signals are absent during the apnea, the event is central. Esophageal manometry (the gold standard) confirms borderline cases by directly measuring intrathoracic pressure swings. In practice, most labs score from RIP; look for the effort bands in the raw tracing rather than relying solely on the summary AHI breakdown.
- Effort present, airflow absent— obstructive apnea. The brain is signaling; the airway is not responding.
- Effort absent, airflow absent— central apnea. The brainstem has temporarily suspended the ventilatory rhythm.
- Mixed apnea— begins without effort (central component) then effort resumes before airflow returns (obstructive component). Scored as mixed; counts toward the overall AHI.
- Complex sleep apnea (treatment-emergent CSA) occurs when CPAP therapy suppresses OSA but unmasks central events — re-evaluate after 4–8 weeks of CPAP use before switching devices.
Related Resources
Sources
- Kacmarek RM, Stoller JK, Heuer AJ. Egan's Fundamentals of Respiratory Care. 12th ed. Elsevier; 2021.
- Berry RB, Quan SF, Abreu AR, et al. The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology and Technical Specifications. Darien, IL: American Academy of Sleep Medicine; 2020.
- Aurora RN, Chowdhuri S, Ramar K, et al. The treatment of central sleep apnea syndromes in adults: practice parameters with an evidence-based literature review and meta-analyses. Sleep. 2012;35(1):17-40.