iPhone / iPhone Duo Live
Last night before you are out of bed. Apple Health vitals, Face ID.
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Summary numbers tell you how a night went. The waveform shows why. Once you can recognise a handful of shapes, a night that looked odd on the dashboard often explains itself in a minute of scrolling.
Key takeaways
- Flow shows each breath as a wave: up for breathing in, down for breathing out.
- Pressure shows what the machine delivered; on an auto machine it moves, on a fixed machine it is a flat line.
- Leak shows air escaping around the mask; a plateau and a spike mean different things.
- Event flags are the machine's best guess. Look at the shape underneath before you trust a label.
The three traces
Flow is the breath itself. Each cycle rises as you inhale and falls as you exhale, so a healthy trace looks like a steady, rounded wave. Pressure is what the blower delivered; a fixed-pressure machine draws a straight line, an auto machine climbs and falls in response to what it sees. Leak is the unintentional air escaping around the mask, in litres per minute. Our guide to CPAP leak rate explains the numbers, and pressure settings explains what moves the pressure trace.
Shapes worth knowing
| What you see | What it usually means |
|---|---|
| Even, rounded waves | Open airway and a comfortable seal |
| Flat-topped waves | Flow limitation: the airway is partly narrowed on the way in |
| Waves shrinking, then flattening | A hypopnea (reduced flow) or an apnea (near-flat trace) |
| Sawtooth ripples at the top of the breath | Snoring |
| Leak jumps, then returns | A position change or a mask knocked loose |
| Leak plateau that starts mid-night | Often a mouth leak with a nasal mask |
The machine marks apneas and hypopneas for you, but flags are a classification, not a diagnosis. When a flag looks wrong, a leak spike nearby is the first thing to check, because high leak makes events harder to score. ResMed marks events during large leak as unclassified.
How to read a night in five minutes
- Start at the summary and note anything unusual: a high-leak stretch or a cluster of events.
- Zoom to that stretch and read the leak first. If it is high, the rest of the trace is less reliable.
- Look at flow: is it flat-topped before events, which suggests the airway narrowing first?
- Check pressure: did the machine respond, and did events continue anyway?
- Note the time, and compare it with what you were doing (position, alcohol, congestion).
Waveform viewing is a Pro feature in Apnealytics, and it reads ResMed machines today. The breath-by-breath viewer page shows how events, a crosshair readout and a leak band work together.
What a waveform cannot tell you
A trace shows airflow, not sleep stage or oxygen. For oxygen, pair it with an oximeter (SpO₂, ODI and T90). For how this fits your longer-term picture, see your 30-day AHI trend.
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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