What do SpO2, PR, PI and the other readings on a pulse oximeter mean?
Find it by its shape. 1. Pick what you see on the oximeter’s screen. 2. Match the drawing. Each reading or symbol here is backed by the manuals of at least two different maker groups (Nonin, Masimo, Beurer, Microlife), and every oxygen or pulse threshold and every piece of health wording is quoted with the name of the maker that printed it.
Check your oximeter’s manual — makers differ.
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.
Tap a shape — the symbols that use it appear here.
SpO₂, PR or PI — 3 symbols
SpO2 on a pulse oximeter (oxygen saturation, %SpO2)One of the two main numbers, marked %SpO2 or SpO2 beside it or in…PR or bpm on a pulse oximeter (pulse rate)The second main number, marked PR, PRbpm or bpm, usually below or…PI or Pi on a pulse oximeter (perfusion index)A smaller third number marked PI or Pi, usually with a % sign,…
Wave or bar — 2 symbols
Dashes or signal light — 3 symbols
Bar graph on a pulse oximeter (pulse bar)A column of blocks or a single bar beside the numbers that jumps…Weak or poor signal indicator on a pulse oximeterA small light that changes colour, numbers that turn dim, or a…Dashes instead of numbers on a pulse oximeter (no reading)Short horizontal dashes where the SpO2 and pulse numbers should be.
Words or codes — 2 symbols
Battery — 1 symbol
Screen turned — 1 symbol
Before you trust any chart, including this one
No published standard we could check defines what a fingertip oximeter’s display shows. ISO 80601-2-61, the international standard for pulse oximeters that Nonin’s and Microlife’s manuals cite, sets accuracy and safety requirements and is sold rather than published free, so we could not check what, if anything, it says about display symbols. Every meaning on these pages is taken from makers’ own manuals.
- The two big numbers are the same on every oximeter read: the one marked %SpO2 is oxygen saturation, the one marked PR or bpm is pulse rate. A third number marked PI, on Beurer’s PO 45 and Masimo’s MightySat, is the perfusion index, which is about the signal at the finger rather than oxygen.
- The wave and the bar describe the signal, not the heart. Beurer’s PO 30 manual says neither display “allows the strength of the pulse or circulation to be evaluated at the measurement site”; Masimo’s manual says the bar’s height shows its confidence in the reading.
- A number is only as good as the signal behind it. Nonin says to watch about 4 seconds of steady green on the Onyx Vantage 9590’s pulse quality light before relying on the values, and Microlife says the OXY 300’s bar should be greater than 30% for a proper reading.
- Only one of the makers cited prints a table of what the oxygen numbers mean: Beurer’s PO 30 and PO 45 manuals, and Beurer says its table does not apply to people with conditions such as asthma or heart failure, or above 1500 metres. The SpO2 page quotes that table with Beurer’s name on it.
- None of these fingertip oximeters is a monitor. Nonin, Beurer and Microlife all say theirs has no alarm and is for spot checks; Microlife’s OXY 200 beeps as a “risk reminder” but its manual still says it has no alarm system for SpO2 or pulse rate.
Maker by maker
- Nonin. Two editions of the instructions for the Onyx Vantage 9590 finger oximeter were read: the full leaflet (P/N 10906-001-04, 2020) and the shorter 2022 edition (P/N 114847-000-02). The 9590 shows two numbers and a tricolour pulse quality light; it has no wave, no bar and no PI, and it shows low batteries by flashing its numbers.
- Masimo. The operator’s manual (LAB-9121C) and the home care manual of the MightySat Rx were read from Masimo’s own document server. The MightySat shows SpO2, PR and Pi, and optionally PVi and a respiration rate; its screen can show a waveform or a pulse bar, dims its numbers when confidence is low, and turns its screen clockwise at a tap.
- Beurer. Three manuals were read: the PO 30 (2020) and PO 45 (2020) European instructions and the PO 60 US manual. The PO 45 adds a PI value and a symbol for an inaccurate measurement; the PO 30 and PO 45 print Beurer’s SpO2 evaluation table. The PO 45 manual was downloaded through the link on Beurer’s product page, which points to Beurer’s image server at Cloudinary.
- Microlife. The OXY 300 (revision 2023-11-30) and OXY 200 (2026-09-14) manuals were read. The OXY 300 writes Finger Out and numbered errors on an OLED screen with six display modes; the OXY 200 shows dashes when the signal is weak and beeps for low readings.
Related pages
What these pages cannot do
- They do not identify a specific pulse oximeter model. They say what a symbol means on the makes cited (Beurer, Masimo, Microlife, Nonin); your model’s manual gives its own display ranges, switch-off time, error codes and display modes.
- They cannot tell you whether an oxygen or pulse reading is fine for you. Beurer prints an evaluation table and Masimo tells you to “Always consult your doctor”; where a page quotes a maker on this, it names the maker.
- They cannot check your oximeter’s accuracy. Nonin and Masimo publish accuracy figures for their own models, quoted on the SpO2 page; Nonin’s manual adds that a functional tester “cannot be used to assess the accuracy of a pulse oximeter monitor”.
- They do not cover hospital bedside monitors, wrist or ring oximeters, smartwatches, or the makers’ phone apps.
- Left out: No SpO2 alarm mark on the label. Nonin (“no alarm for SpO2”), Beurer (“SpO2 Alarm suppression”) and Microlife (“No SpO2 alarm”) all list it in their symbol tables, but the copies we read name it without a drawing we could check, so it gets no page. It says the oximeter has no oxygen alarm at all; the related alarm off mark used on monitors that do have alarms is explained on /medical/alarm-off/.
- Left out: Heart or pulse-beat icon. None of the manuals read shows a separate heart icon; the pulse is shown by the blinking light, wave or bar instead, which have their own pages.
- Left out: PVi and RRp. Only Masimo’s MightySat shows the pleth variability index and a respiration rate among the oximeters read, so there is no second maker group to confirm them.
- Left out: Bluetooth, sync and brightness indicators. They say whether the oximeter is talking to a phone app or how bright the screen is, not anything about the reading; Beurer’s and Masimo’s manuals explain them.
- Left out: Marks printed on the oximeter and its box (type BF, read the instructions). They are standard medical-device symbols that already have their own pages on this site, linked under Related pages above, so they are not repeated here.
Sources
Every document below is a maker’s own manual or support page, fetched and read on the date shown. Each symbol page quotes what its sources show.
- Nonin: Nonin Onyx Vantage 9590 finger pulse oximeter — instructions for use (P/N 10906-001-04, 2020, PDF) Checked 2026-09-29.
- Masimo: Masimo MightySat Rx fingertip pulse oximeter — operator’s manual (LAB-9121C, PDF) Checked 2026-09-29.
- Masimo: Masimo MightySat Rx fingertip pulse oximeter — home care manual (PDF) Checked 2026-09-29.
- Beurer: Beurer PO 30 pulse oximeter — instructions for use (2020-01-08, German/English, PDF) Checked 2026-09-29.
- Beurer: Beurer PO 45 pulse oximeter — instructions for use (2020-06-12, German/English, PDF linked from beurer.com) Checked 2026-09-29.
- Microlife: Microlife OXY 300 fingertip pulse oximeter — instruction manual (IB OXY 300 N-V9, revision 2023-11-30, PDF) Checked 2026-09-29.
- Microlife: Microlife OXY 200 fingertip pulse oximeter — instruction manual (IB OXY 200 S-V10, 2026-09-14, PDF) Checked 2026-09-29.
- Beurer: Beurer PO 60 pulse oximeter — US instruction manual (English/French/Spanish, PDF) Checked 2026-09-29.
- Nonin: Nonin Onyx Vantage 9590 — instructions for use leaflet (P/N 114847-000-02, 11/2022, PDF) Checked 2026-09-29.