By PulsHealth. Updated
Research reviewed .
What does peripheral perfusion index mean?
Peripheral Perfusion Index describes pulse strength at the monitoring site. It is a discrete percentage quantity in HealthKit. In pulse-oximeter terminology, the index compares the pulsatile signal with the nonpulsatile signal at the sensor. It is an indirect local indicator rather than a direct measurement of blood flow through the whole body. Apple defines the quantity.
Why can the stored number look 100 times smaller?
HealthKit's percent unit uses a fractional representation. For example, 0.02 represents 2% when formatted for display. This is a unit-conversion example, not an observed reading. An export or chart must state whether it shows the raw fraction or a percentage number; applying the conversion twice creates a 100 fold error.
| Number or field | How to read it |
|---|---|
| Raw HealthKit fraction 0.02 | Display as 2% |
| Displayed 2% | Do not treat as raw fraction 2 |
| Oxygen saturation | A separate quantity, even if also a percentage |
| Sensor site and method | Needed for meaningful comparisons |
Is there a universal normal range?
The quantity alone does not define a universal clinical threshold. A manufacturer's manual describes its particular device's numeric display and sensitivity to changes in physiology and blood flow at the monitoring site. A display range or a threshold used in a particular clinical study should not become a general normal/shock table for all HealthKit data.
Review probe placement, site, device and recording conditions before interpreting a change. A changing peripheral reading can have several explanations, so the index alone cannot diagnose circulation problems or determine treatment.
How should cadence and related readings be analyzed?
Sources may save spot readings, monitoring intervals or summaries; HealthKit does not guarantee a fixed schedule. An apparent gap may be absent logging rather than a physiological change. For trends, compare the same site and method, keep gaps visible and distinguish a sample average from a duration-weighted monitoring summary.
Oxygen saturation and heart rate can add context if both were recorded with adequate coverage. Matching timestamps alone do not establish a shared probe, validate oxygen-saturation accuracy or show why the index changed.
What did the coverage review find?
The reviewed 365-day example-data window contained no samples, stored aggregates or workout-series points for this type. Value distributions, unusual readings, recording cadence and related-data comparisons could not be measured. No empirical figure is presented; missing database rows do not establish missing records on the phone.
Does PulsHealth collect this type?
The current PulsHealth sync catalog includes this type in %. Database coverage and Apple Health availability are separate questions.
Understanding your records
Recording frequency, source and coverage affect what you can conclude from this data. Read the recording guide.
- One record
- Pulse strength expressed using fractional HealthKit percent units;0.02 represents2% when displayed as a percentage.
- Frequency
- Source-dependent contributions, spot readings or recorded intervals; no empirical cadence was available.
- Context
- Interpret timing and source method for the specific measurement; timestamp overlap does not establish shared session identity.
- Coverage and gaps
- No observations in the reviewed reporting window; database absence is not a zero reading or proof of absence on the phone.
- Summaries
- Discrete values are not cumulative totals. Use compatible units, durations, coverage and source methods for summaries.
- Metadata
- Optional source metadata does not establish complete measurement method or context; no records were available to inspect.
Recording guidance reviewed 2026-10-14