By PulsHealth. Updated
Research reviewed .
What does peak expiratory flow measure?
Peak expiratory flow is the highest flow reached during a forceful exhalation. HealthKit stores a discrete volume-per-time quantity, commonly displayed in liters per minute. Unlike FEV1, it is a flow rate rather than the total volume exhaled over a fixed interval.
What is a useful comparison range?
A generic adult range can be misleading. Technique, equipment and individual characteristics matter, and an asthma action plan may use a personal baseline and agreed zones. NHLBI recommends keeping peak-flow results to compare them over time with the care plan. A missing measurement is not evidence that airflow was normal.
| Context | Why it matters |
|---|---|
| L/min versus L/s | Multiply L/s by 60 to express the same flow in L/min. |
| Same device and technique | A different method can disrupt comparisons. |
| Individual attempts versus selected result | Several blows may represent one test session. |
| Time and medication context | Measurements under different conditions may not be directly comparable. |
Why might several readings occur close together?
A measurement routine may include repeated blows and a selected result. The writing app can preserve the attempts or only that result; rows therefore do not establish session count. Follow the measurement instructions agreed with the provider and inspect source context before combining imports or calculating trends.
How does peak flow relate to symptoms and inhaler use?
Inhaler logs and breathing symptoms can help describe the circumstances around readings. A nearby count does not establish medication identity, dose or a treatment effect. Comparisons need compatible testing conditions and known timing, rather than automatic pairing of the nearest samples.
Peak flow is one part of an individual asthma action plan. The graph alone cannot diagnose asthma or set treatment changes.
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