What you should learn
Tell central, obstructive, and mixed patterns apart.
Make sure the effort belts are trustworthy before calling an event central.
Understand CO₂ control, periodic breathing, and TECSA in simple terms.
Know what the technologist checks, documents, and escalates.
1. Start with one question: Is the patient trying to breathe?
Airflow alone does not tell you whether an apnea is central. You must look at breathing effort too.
| Pattern | Airflow | Effort | Easy way to remember |
|---|---|---|---|
| Obstructive apnea | Stops | Continues | The patient is trying to breathe against a blocked airway. |
| Central apnea | Stops | Stops | Airflow and breathing effort pause together. |
| Mixed apnea | Stops | Absent first, then returns | It starts central and then looks obstructive. |
2. Why central breathing can become unstable
Your brain uses carbon dioxide (CO₂) as one signal for how strongly to breathe. During sleep, some people are more likely to cross a level where the breathing drive briefly pauses. That level is called the apneic threshold.
Loop gain is a way to describe how strongly the breathing-control system reacts to change. A very “touchy” system can overshoot: breathing rises, CO₂ falls, breathing drops, CO₂ rises, and the cycle repeats.
3. Treatment-emergent central sleep apnea (TECSA)
A patient may start PAP because of obstructive sleep apnea. The obstruction improves, but central events appear or become more noticeable. This is called treatment-emergent central sleep apnea.
4. Periodic breathing and Cheyne-Stokes breathing
Periodic breathing is easier to see when you look at several minutes instead of one 30-second epoch. The breaths slowly get larger, then smaller, and the pattern repeats. Cheyne-Stokes breathing is a specific periodic breathing pattern that includes central events and is often discussed with cardiovascular disease.
5. Coach Bob PSG Case Lab
These are original teaching traces. They are simplified to train pattern recognition, not to replace the current scoring manual.
Case 1: What kind of apnea?
Case 2: Can you trust the effort signal?
The thorax belt becomes almost flat even during breaths that are clearly visible on the other signals and video.
Case 3: PAP changes the pattern
Snoring and obstructive events improve on PAP. New pauses now show loss of both airflow and effort.
Case 9: What do you see when you zoom out?
Start with this 30-second view. Then zoom out to see the larger breathing pattern.
6. Technologist workflow
- Review the order and available history.
- Make sure airflow, thorax, abdomen, SpO₂, and ordered CO₂ channels are reliable.
- Classify the pattern using airflow and effort together.
- Widen the time window when periodic breathing is suspected.
- During PAP, ask what changed: obstruction, leak, oxygenation, ventilation, or respiratory drive?
- Correct artifact before drawing conclusions.
- Document what you observed and follow the physician order and laboratory protocol.
7. Word of the Day
How strongly the breathing-control system responds to chemical signals such as CO₂ and oxygen.
Coach Bob memory hook: “Chemo = chemicals. Sensitivity = how strongly the system reacts.”
8. Suggested flashcards
Central apnea
Airflow and inspiratory effort are absent during the event.
Mixed apnea
Starts with absent effort; effort returns before airflow.
TECSA
Central events that emerge or become prominent when PAP treats obstructive sleep apnea.
Apneic threshold
A CO₂ level below which breathing drive may pause during sleep.
Loop gain
A way to describe how strongly the breathing-control system reacts to a disturbance.
Periodic breathing
A repeating rise and fall in ventilation over time.
Cheyne-Stokes breathing
A specific waxing-and-waning periodic breathing pattern associated with central events.
Backup rate
Timed breaths delivered when spontaneous breathing is too slow or absent, depending on mode and settings.
ASV
Adaptive servo-ventilation; an advanced PAP mode that changes support in response to unstable breathing.
Signal integrity
Confidence that the sensor is actually measuring what it is supposed to measure.
9. Glossary
- Central sleep apnea (CSA)
- A sleep-related breathing disorder with repeated central respiratory events.
- Respiratory effort
- The body’s attempt to breathe, usually followed with thoracic and abdominal effort signals.
- RIP
- Respiratory inductance plethysmography; a common method for measuring chest and abdominal effort.
- TECSA
- Treatment-emergent central sleep apnea.
- Hypocapnia
- A lower-than-normal carbon dioxide level.
- Hyperpnea
- Breathing that becomes deeper or greater than baseline.
- Periodic breathing
- A repeating pattern of rising and falling ventilation.
- Cheyne-Stokes breathing
- A specific periodic breathing pattern with waxing and waning ventilation and central events.
- Apneic threshold
- The CO₂ level below which stable breathing drive may stop during sleep.
- Chemosensitivity
- How strongly respiratory control responds to chemical changes such as CO₂.
- Loop gain
- A measure of how strongly a control system responds to a disturbance.
- ASV
- Adaptive servo-ventilation.
- Backup rate
- A timed breath rate used in selected PAP modes.
- Transvenous phrenic nerve stimulation
- An implanted treatment that stimulates the phrenic nerve to support breathing in selected patients with CSA.
10. Related Sleep Pathways Guild learning
Common PAP failures
Review problems that can appear during PAP therapy, including central-event concerns.
Read article →11. Practice with our free webapps
Free RPSGT Study Webapp
Practice questions, skill labs, reports, and exam-prep tools.
Open RPSGT Webapp →12. Go deeper with a book
Want a textbook beside you while you study? Visit the Sleep Pathways Guild curated RPSGT Book Store for books on polysomnography, respiratory physiology, PAP therapy, and sleep medicine.
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13. APA references
- American Academy of Sleep Medicine. (2023). The AASM manual for the scoring of sleep and associated events: Rules, terminology and technical specifications (Version 3).
- Badr, M. S., Khayat, R. N., Allam, J. S., et al. (2025). Treatment of central sleep apnea in adults: An American Academy of Sleep Medicine clinical practice guideline. Journal of Clinical Sleep Medicine, 21(12).
- Javaheri, S., & Badr, M. S. (2023). Central sleep apnea: Pathophysiologic classification and related concepts.
- Robertson, B., Marshall, B., & Carno, M.-A. (2014). Polysomnography for the sleep technologist: Instrumentation, monitoring, and related procedures. Elsevier.
- American Academy of Sleep Medicine. (2023). International classification of sleep disorders (3rd ed., text revision).
Independent educational resource. Sleep Pathways Guild is not affiliated with or endorsed by BRPT, AASM, AAST, or an examination provider. Use the current scoring manual, physician orders, device instructions, laboratory policy, and clinical supervision for patient care.