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Peak flow measurement animated demonstration

Equipment needed

Apply a new disposable mouthpiece and filter if multiple patients use one device.

Check that the patient has a baseline peak expiratory flow (PEF). Obtain this either from their medical records - a personal best recorded within the last two years - or, if they have not measured their PEF within the last two years, calculate it from a predicted PEF chart. In the case of the latter, note the patient’s age, sex, and height.

Contraindications

As with any procedure, clinicians should not perform measurement of the PEF where there is lack of consent or understanding by the patient. PEF measurement is safe and non-invasive, but its accuracy depends on expiratory effort from the patient. Therefore, it may be unsuitable or impractical for young children and patients who are confused.

Indications

PEF provides a measure of airflow obstruction and may be indicated in the diagnosis and management of asthma.

PEF measurement should be performed in:[65]Pollart SM, Compton RM, Elward KS. Management of acute asthma exacerbations. Am Fam Physician. 2011 Jul 1;84(1):40-7. https://pubmed.ncbi.nlm.nih.gov/21766754 http://www.ncbi.nlm.nih.gov/pubmed/21766754?tool=bestpractice.com

• Patients presenting with an acute asthma attack. Measurement of the PEF helps to gauge the severity of the attack and inform management

PEF measurement should be considered in:[66]National Institute for Health and Care Excellence. Asthma: diagnosis, monitoring and chronic asthma management (BTS, NICE, SIGN). Nov 2024 [internet publication]. https://www.nice.org.uk/guidance/ng245 [67]Vandenplas O, Suojalehto H, Cullinan P. Diagnosing occupational asthma. Clin Exp Allergy. 2017 Jan;47(1):6-18. https://www.doi.org/10.1111/cea.12858 http://www.ncbi.nlm.nih.gov/pubmed/27883240?tool=bestpractice.com

• Developing a personalised action plan for adults with asthma. The plan may also be symptom-based

• Adults with a possible diagnosis of asthma. PEF to measure airflow variability may be used to corroborate a history of recurrent episodic symptoms. Multiple measurements are made over at least two weeks; increased variability may be evident from twice-daily readings.

• Patients with suspected occupational asthma. Serial PEF readings are taken four times per day, both at work and away from work.

Complications

None

Aftercare

None