By PulsHealth. Updated
Research reviewed .
What does FEV1 measure?
FEV1 is the air volume exhaled during the first second of a forced breathing test. HealthKit stores a discrete volume, usually displayed in liters. It is different from peak expiratory flow, which measures the fastest flow rather than volume.
How should I read a spirometry result?
A raw liter value has no universal adult normal range. Interpretation needs the test report, measurement quality and an appropriate reference equation. Percent predicted and a z-score are derived interpretations, not the raw HealthKit quantity. The ATS recommends race-neutral reference interpretation; the equation used matters when comparing reports.
| Context to retain | Why it matters |
|---|---|
| Liters or milliliters | 1 L equals 1,000 mL; unit errors can look like dramatic changes. |
| Test session and quality | Several attempts may belong to one session; a low-effort attempt differs from a usable result. |
| Before or after bronchodilator | These are distinct test conditions. |
| Reference equation | A changed equation can alter percent predicted without changing the measured volume. |
Can I calculate FEV1/FVC from HealthKit?
Only when FEV1 and FVC can be assigned to the same test session and condition. Spirometry standards use the largest acceptable FEV1 and FVC for that session; they need not come from the same maneuver. Pairing unrelated daily averages or simply choosing the nearest timestamps can produce a misleading ratio. A matching timestamp alone does not establish a shared test.
Why can recordings appear in clusters?
Spirometry is a deliberate test. An app may save each attempt or only the selected result, so row counts need not equal test-session counts. Source app, device and available report context help distinguish repeated attempts, imports and follow-up visits. A gap in HealthKit does not establish a period of normal lung function.
Does PulsHealth currently collect this type?
This HealthKit type is not listed in the current PulsHealth sync catalog. Its presence in this reference does not promise collection. Database absence does not establish absence in Apple Health.
Understanding your records
Recording frequency, source and coverage affect what you can conclude from this data. Read the recording guide.
- One record
- Discrete deliberate-test result; repeated attempts may belong to one measurement session.
- Frequency
- Source-specific testing or logging cadence; row count need not equal event or test-session count.
- Context
- Preserve testing conditions or reliable medication context; timestamps alone cannot establish a physiological response.
- Coverage and gaps
- No observations in the reviewed database window; this does not establish absence in Apple Health or normal physiology.
- Summaries
- Keep units and test sessions compatible. Selected session results differ from averages of individual attempts.
- Metadata
- No sample metadata available to inspect. Raw values cannot establish test quality or medication identity.
Recording guidance reviewed 2026-10-14