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# peakExpiratoryFlowRate

A quantity sample type that measures the user’s maximum flow rate generated during a forceful exhalation.

```
static let peakExpiratoryFlowRate: HKQuantityTypeIdentifier
```

## Discussion

These samples use volume/time units (described in [`HKUnit`](/documentation/HealthKit/HKUnit)) and measure discrete values (described in [`HKQuantityAggregationStyle`](/documentation/HealthKit/HKQuantityAggregationStyle)).

---

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