Most modern CPAP machines and their apps show an AHI each morning. A high number can be worrying, but it’s a reason to troubleshoot, not to panic.
What the numbers mean
The AASM’s PAP titration guidelines define the terms (AASM, J Clin Sleep Med 2008):
- AHI: total apneas plus hypopneas per hour of sleep.
- RDI: apneas, hypopneas and respiratory effort-related arousals (RERAs) per hour.
The same guideline grades adult OSA severity by RDI:
| Severity | RDI (events per hour) |
|---|---|
| Mild | 5 to 15 |
| Moderate | 15 to 30 |
| Severe | Over 30 |
What “controlled” looks like
- Titration target. The pressure chosen after titration should reflect control of obstructive breathing by “a low (preferably under 5 per hour)” RDI. That’s alongside a minimum sea-level SpO₂ above 90% and leak within acceptable parameters (AASM titration guideline).
- Auto CPAP. The AASM’s review of auto-titrating CPAP says an AHI under 10 per hour on CPAP or APAP “was considered an acceptable outcome” as a historical standard. It adds that “reductions to less than 5/hr … may be required for reversal of sleepiness in individual patients” (AASM review).
- Follow-up. The AASM’s 2019 PAP guideline says follow-up should include “troubleshooting and monitoring of objective efficacy and usage data” (AASM 2019 guideline).
Your clinician decides your target. These figures show what the guidelines aim for, not a diagnosis.
Why your AHI might be high
| Possible cause | How to check | What to try |
|---|---|---|
| Large mask or mouth leak | Leak figure in your machine or app. The AirSense 11 notes its results may be inaccurate with leaks | Fix mask leaks; chin strap or full face mask for mouth leak |
| Mask shifted, or a worn or damaged cushion | Leak spikes during the night; cushion torn, cracked or discolored | Refit; replace the cushion (ResMed troubleshooting guide) |
| Tub or tube not connected properly | ”High leak detected” messages | Reseat the humidifier tub; connect the tube firmly at both ends |
| One-off bad night | AHI high on a single night only | Watch the trend over several nights |
| Settings no longer right for you | Symptoms not improving | MedlinePlus: settings may need to be changed. Clinician review |
| Supplemental oxygen bled into CPAP | The AirSense 11 notes results may be inaccurate with supplemental oxygen | Tell your clinician |
Sources: ResMed AirSense 11 user guide.
What to bring to your clinician
- At least 2–4 weeks of data: usage hours, AHI, leak and pressure, from the machine, its app or the SD card.
- Your mask and how long you’ve had the cushion.
- Symptoms: sleepiness, snoring your partner notices, morning headaches.
- Questions: what target your clinician wants, and whether you need a repeat study.
If you’re on Medicare and inside the first 90 days, the follow-up between day 31 and day 91 must document that your symptoms have improved, not just that you used the machine (Medicare CPAP guide).
If symptoms don’t improve
MedlinePlus says that if your symptoms don’t improve on PAP, the settings may need to be changed. Your provider may teach you how to adjust them at home, or you may need to go back to the sleep center (MedlinePlus).
Verdict
Look at the trend over several nights, not one bad night. Check leaks first, because they can push the AHI up and make the reading less reliable. If your AHI stays above your clinician’s target with good leak and usage, take the data to your sleep clinician. Don’t adjust pressure yourself.