From the Guidelines
When doing peak flow, you should take the best of three attempts rather than the average of three readings. This is based on the most recent and highest quality study, which states that the best of three attempts is taken and compared with charts of normative data for sex, age, and height 1. To perform peak flow measurement correctly,
- stand up straight,
- reset the peak flow meter to zero,
- take a deep breath,
- place the mouthpiece in your mouth with a tight seal, and
- blow out as hard and fast as possible. Repeat this process two more times for a total of three measurements, and record the highest reading as your peak flow value.
This approach is supported by the european position paper on rhinosinusitis and nasal polyps 2020, which suggests that the best of three attempts is used to assess peak flow, and a 20% increase and absolute improvement of 60l/min is suggestive of asthma though the diagnosis cannot be made on a single test 1.
Some key points to keep in mind when performing peak flow measurements include:
- Patients can be prescribed a peak flow meter and chart on which they can record their daily measurements, ideally performed at the same time morning and evening.
- Average daily diurnal variation is calculated as the day’s highest PEF minus the day’s lowest PEF, divided by the mean PEF for the day and then averaged over the course of a week.
- A variability of >10% in adults and >13% in children is suggestive of asthma 1.
By following these guidelines and taking the best of three attempts, you can ensure accurate and reliable peak flow measurements that can help monitor asthma or other respiratory conditions.
From the Research
Peak Flow Measurement
- The procedure for measuring peak expiratory flow rate (PEFR) involves using a peak flow meter to record the maximal flow rate of air that can be achieved in one forceful expiration following a full inspiration 2.
- To achieve accurate results, it is necessary to use the correct technique, and nurses should have the knowledge and skills required to obtain a patient's PEFR safely and effectively 2.
- Patients and/or carers should be taught how to perform the test themselves so that they can self-manage and monitor conditions such as asthma and chronic obstructive pulmonary disease 2.
Taking Readings
- The provided studies do not specifically mention taking the average of three readings when doing peak flow 2, 3, 4, 5, 6.
- However, it is generally recommended to take multiple readings to ensure accuracy, but the exact number of readings is not specified in the provided studies.
Importance of Accurate Measurement
- Measuring PEFR is an inexpensive, straightforward, and useful clinical investigation that enables fluctuations in the patient's respiratory effort to be monitored over time 5.
- Accurate assessment and recording of PEFR can enable significant improvements in patient care, and nurses should advise patients on the action required if variation between readings occurs 5.