6.2 Split-Night and Titration Studies, PAP-NAP, Oximetry & Explaining Results
Key Takeaways
AASM practice parameters support a split-night study when the AHI is at least 40 during at least 2 hours of diagnostic recording (20–40 by clinical judgment) and at least 3 hours remain for titration.
A titration study finds the pressure or mode that controls breathing events in all positions and sleep stages; home APAP is an alternative for uncomplicated OSA.
The PAP-NAP is a daytime session that combines mask desensitization, coaching and a nap on PAP to help anxious or insomnia patients accept therapy.
Overnight oximetry reports the oxygen desaturation index, nadir and time below 90%, but cannot diagnose OSA on its own and may overestimate saturation in people with darker skin.
The CCSH can explain what AHI, oxygen nadir and severity categories mean, but the physician makes and communicates the diagnosis.
6.2 Split-Night and Titration Studies, PAP-NAP, Oximetry & Explaining Results
Domain 2, Task C asks the CCSH to discuss testing indications and results, naming in-lab PSG, split-night and titration studies, HSAT, MSLT/MWT, actigraphy and "other procedures (e.g., PAP-NAP, pulse oximetry)." The diagnostic testing section covers PSG, HSAT, MSLT/MWT and actigraphy; this section covers the rest and how results are explained.
Split-Night Studies
A split-night study uses the first part of the night for diagnosis and the rest for PAP titration, saving a second night.
| Requirement (AASM practice parameters) | Detail |
|---|---|
| Diagnostic portion | At least 2 hours of recording |
| Severity | AHI of at least 40 per hour during the diagnostic portion; 20–40 may qualify by clinical judgment (for example, with long events or severe desaturation) |
| Titration time | At least 3 hours of titration should remain |
| Effective titration | Events must be eliminated or nearly eliminated in REM and NREM sleep, including supine REM |
| If criteria are not met | A separate full-night titration is scheduled |
The AASM's 2017 diagnostic guideline suggests using a split-night protocol rather than a full-night diagnostic study when clinically appropriate. Medicare allows an AHI calculated from less than 2 hours of sleep only if the number of events is at least what would be needed over 2 hours.
Educating patients: explain before the study that the technologist may start PAP partway through the night, show the mask in advance, and practice wearing it. Patients who are surprised by a mask at 2 AM often refuse it.
Full-Night Titration Studies
An attended titration study adjusts pressure (CPAP or bilevel), backup rate (bilevel S/T or ASV) and sometimes oxygen to find settings that control apneas, hypopneas, RERAs and snoring across positions and sleep stages. Titrations for hypoventilation use carbon dioxide monitoring (transcutaneous or end-tidal). The PAP section explains the AASM titration algorithm and quality grades (optimal, good, adequate, unacceptable).
For adults with uncomplicated moderate-to-severe OSA, the AASM's 2019 PAP guideline recommends starting either with home APAP or with in-lab titration. In-lab titration is preferred for patients with significant heart or lung disease, hypoventilation, central apnea or failed home therapy.
PAP-NAP
The PAP-NAP (described by Krakow and colleagues in 2008) is a daytime, abbreviated titration session for patients with claustrophobia, anxiety, PTSD or insomnia who are reluctant to try PAP. It combines:
- education and mask fitting;
- desensitization while awake (breathing on PAP while relaxed, with coaching); and
- a monitored daytime nap on PAP, so the patient experiences sleep with therapy.
In published case series it improved PAP acceptance and adherence in these groups. It is a therapeutic and educational tool, not a diagnostic test, and it does not replace a full titration when one is needed.
Overnight Pulse Oximetry
Pulse oximetry measures oxygen saturation (SpO2) and pulse through a finger or ear probe.
| Measure | Meaning |
|---|---|
| Oxygen desaturation index (ODI) | Desaturations of 3% or 4% per hour of recording |
| Nadir SpO2 | The lowest saturation recorded |
| T90 | Time (or percentage of time) with SpO2 below 90% |
| Pattern | A repeated "sawtooth" pattern suggests cyclic apneas; long, sustained dips (often in REM) suggest hypoventilation or lung disease |
Uses: monitoring oxygen therapy, checking oxygen levels on PAP, qualifying patients for home oxygen under payer rules, and screening in limited-resource settings.
Limits:
- The AASM does not recommend oximetry alone to diagnose OSA; it misses hypopneas that cause arousals without desaturation and cannot separate central from obstructive events.
- Motion, poor circulation, cold fingers, nail polish and carbon monoxide distort readings.
- In 2021 the FDA warned that pulse oximeters may be less accurate in people with darker skin pigmentation, tending to overestimate saturation, so a "normal" reading may hide low oxygen.
Explaining Results in Collaboration With the Provider
The blueprint says "explain results in collaboration with a provider." The physician diagnoses and decides treatment; the CCSH helps the patient understand what the physician has explained and what the numbers mean.
| Report item | Plain-language explanation |
|---|---|
| AHI | "On average, your breathing stopped or became very shallow 32 times an hour while you slept." |
| Severity | Normal under 5; mild 5–14.9; moderate 15–29.9; severe 30 or more per hour (adults) |
| REI (home test) | Like the AHI but per hour of recording time, so it can underestimate severity |
| Nadir SpO2 / T90 | "Your oxygen dropped as low as 78%, and it was under 90% for 45 minutes." |
| Supine or REM AHI | Whether apnea is worse on the back or in dream sleep, which can guide positional therapy |
| Central apnea index | How many pauses happened without breathing effort |
| Sleep efficiency, arousal index | How continuous the sleep was |
| Titration pressure | The setting that kept the airway open |
Good practice:
- Confirm what the physician has already told the patient, then explain and use teach-back.
- Avoid stating a diagnosis or prognosis the physician has not made, and route new medical questions to the physician.
- Connect results to the patient's symptoms and goals, and to the treatment plan.
Reading a Sample Report
A split-night study for a 55-year-old man shows:
| Item | Result |
|---|---|
| Diagnostic portion | 2.5 hours of sleep; AHI 58 per hour; nadir SpO2 74%; supine AHI 80 per hour |
| Titration portion | 4 hours; CPAP 5–12 cmH2O; at 11 cmH2O the AHI was 2 per hour, including supine REM |
| Central events on CPAP | Central apnea index under 1 per hour |
| Leak | Acceptable |
How the CCSH might explain it after the physician's review: "In the first part of the night your breathing stopped or became shallow about 58 times an hour, which is severe, and your oxygen dropped to 74%. It was worse on your back. When the technologist started the CPAP, a pressure of 11 kept your airway open, even in dream sleep on your back. Dr. Lee has ordered your machine at that pressure. What questions do you have?"
The CCSH then checks understanding with teach-back and moves on to mask fitting and setup.
During the first 2 hours of a diagnostic PSG, a patient's AHI is 52 events/hour with severe desaturations. Under AASM practice parameters, what may the technologist do if the protocol allows?
End the study at once and send the patient home, since AHI is already known
Convert to a split-night study, provided at least 3 hours remain for PAP titration
Start oxygen alone for the rest of the night instead of attempting any PAP titration
Continue diagnosis all night, since split-night studies are never permitted
A patient's overnight oximetry shows no significant desaturations, but he has loud snoring, witnessed apneas and severe sleepiness. Which statement is accurate?
A normal oximetry study proves that the patient does not have obstructive sleep apnea
Oximetry alone cannot rule out OSA, because it misses arousal-based hypopneas and can be inaccurate
Oximetry is the AASM's preferred test for diagnosing OSA in symptomatic adults
Oximetry reliably separates central from obstructive apneas, so no further diagnostic testing is ever needed
After the physician reviews a PSG with a patient, the patient asks the CCSH what 'AHI 34' means. What is the most appropriate response?
Tell the patient that only the physician can discuss any part of the report, so no explanation at all is allowed
Explain that breathing stopped or became very shallow about 34 times an hour, which is in the severe range
State a new diagnosis of heart failure, since an AHI above 30 always means heart disease
Tell the patient the number is unimportant, since only oxygen levels matter in sleep apnea
Sections you finish are checked off in the contents.