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Your CPAP machine gives you an AHI every morning, and every morning it is tempting to treat it as a verdict. It is better read as a single reading on a long line. The line, the 30-night trend, is where the useful information lives.
Key takeaways
- One high night is normal; a sustained shift over one to two weeks is worth a look.
- Compare your AHI with your own baseline, not just the printed bands.
- Read AHI together with leak and usage hours before drawing a conclusion.
Why a single night misleads
AHI is the number of apneas and hypopneas the machine counts per hour of use. Alcohol, a cold, a late meal, sleeping on your back, a cushion that has gone soft or simple chance can each move one night. A person whose 30-night average is 3 will routinely see nights at 1 and nights at 6. Our explainer on what AHI is covers how the machine arrives at the number and why it is an estimate rather than a lab measurement.
What the 30-night line shows
A rolling average smooths out the noise and shows where you normally sit. That baseline is the thing worth knowing, because "high" and "low" only mean something against it. In Apnealytics the Trends view shows 30, 90 and 365 nights and lets you overlay leak and pressure on the same axis.
| Pattern in the trend | A reasonable first read |
|---|---|
| Flat, low, small wobble | Therapy is stable; nothing to do |
| One spike, then back to normal | A bad night; look for an obvious cause such as illness or alcohol |
| A step up that stays up for one to two weeks | Something changed: mask, cushion, position, weight, medication |
| A slow climb over several weeks | Often a tiring cushion or headgear; check leak first |
| Low AHI but low usage hours | The index is per hour used; short nights hide untreated time |
Read AHI with leak and usage
The most common reason AHI creeps up is leak. When unintentional leak is high, the machine sees less, and event counts can move in either direction. Check the leak line for the same nights before you decide anything about AHI. Usage matters too: an AHI of 2 across three hours is not the same night as an AHI of 2 across seven. If you want the baseline for what counts as a good number on therapy, see what is a good AHI on CPAP.
Look for a shift that lasts, not a night that stands out.
Worth remembering
What to do with a shift
Start with the free fixes: wash and refit the mask, check the cushion, look at the hose. If the trend stays higher after that, or event types change, bring the chart to your clinician. A read-only share link lets them see the same trend you are describing. Do not change pressure settings yourself.
Not medical advice. Apnealytics is a tracking and coaching tool, not a diagnostic device. Machine-estimated numbers are not a clinical diagnosis; talk to your clinician about your therapy.
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Written by
Haniel Singh
Founder of Apnealytics. A CPAP user who builds software, not a sleep physician.
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