Moving wave on a pulse oximeter (pleth waveform)
The wave, called a plethysmographic or pleth wave, draws the light signal the oximeter is reading at the fingertip as it rises and falls with each pulse. A regular wave with evenly spaced peaks means the oximeter is picking up a clean pulse; a flat, jagged or wandering line means it is not.
Check your oximeter’s manual — makers differ.
What it is for
Use it to check the reading before trusting the numbers: keep the hand still until the wave is regular. Beurer’s PO 30 manual says the wave and bar are “exclusively used to display the current visual signal variation at the measurement site and do not enable reliable diagnostics for the pulse”. On the Masimo MightySat the wave is optional: Masimo says that when the waveform option is on, the wave and an SIQ line appear, and “the height of the SIQ line provides an assessment of the confidence in the measurement displayed”.
These pages report what each maker’s manual says and quote it wherever health is involved. They do not diagnose anything, they are not medical advice, and they do not tell you whether an oxygen or pulse reading is right for you or what to do about it; only your own oximeter’s manual and your doctor or nurse can do that for the person you are looking after.
- What it looks like
- A line that moves across the screen and rises with each pulse, like a small heart-monitor trace.
- Names makers use
- Pulse wave (plethysmographic wave) (Beurer PO 30, Microlife OXY 300); Pulse Rate Graph (Beurer PO 60); Waveform, with the SIQ line (Masimo MightySat Rx)
Where makes differ
Not every oximeter has one. Nonin’s Onyx Vantage 9590 shows no wave, only a blinking pulse quality light. Masimo lets you choose between the wave and a pulse bar. Beurer’s PO 30, PO 45 and PO 60 and Microlife’s OXY 300 show both a wave and a bar at once.
What it does not mean
It is not an ECG and does not show the heart’s rhythm or electrical activity. The height of the wave is not the strength of the pulse or circulation: Beurer’s PO 30 manual says neither display “allows the strength of the pulse or circulation to be evaluated at the measurement site”.
Other symbols with the same shapes
Sources
No published standard we could check defines what a fingertip pulse oximeter’s display shows, so this meaning is taken from 3 makers’ own manuals and support pages, each fetched and read on the date shown:
- Beurer: Beurer PO 30 pulse oximeter — instructions for use (2020-01-08, German/English, PDF) — Display description: 3. Pulse wave (plethysmographic wave), 4. Pulse bar; warning that neither display allows the strength of the pulse or circulation to be evaluated and that they “do not enable reliable diagnostics for the pulse”. Checked 2026-09-29.
- Beurer: Beurer PO 60 pulse oximeter — US instruction manual (English/French/Spanish, PDF) — LCD display information: 3. Pulse Rate Graph, 4. Pulse Rate Bar; the same warning on the pulse wave and pulse bar. Checked 2026-09-29.
- Masimo: Masimo MightySat Rx fingertip pulse oximeter — operator’s manual (LAB-9121C, PDF) — MightySat Rx features, item 5: when the waveform option is on, the plethysmographic waveform and SIQ line display; the height of the SIQ line assesses the confidence in the measurement. Checked 2026-09-29.
- Microlife: Microlife OXY 300 fingertip pulse oximeter — instruction manual (IB OXY 300 N-V9, revision 2023-11-30, PDF) — Explanation of symbols: 4 Pulse wave (plethysmographic wave), 5 Pulse bar. Checked 2026-09-29.
Written in our own words; quotations are the makers’ wording.