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Pre‐procedural considerations

Equipment

The mini‐Wright peak flow meter

Peak flow is measured by the patient exhaling as quickly and as forcefully as possible following maximal inspiration; the maximum expiratory flow is measured using a PEF meter and usually occurs early in expiration (West and Luks [210]). The mini‐Wright peak flow meter, which is commonly used today, uses EU scales of measurement ranging from 60 L/min to 800 L/min, which are thought to increase the accuracy of the assessment (Hill and Winter [82], West and Luks [210]).

Patients with their own meter should be encouraged to bring it with them to appointments (NICE [135]). If a patient does not have their own meter then most hospitals and clinics have multiple patient‐use PEF meters that are valved and have disposable single‐use mouthpieces to prevent cross‐infection (British Thoracic Society [30]). Most hand‐held PEF meters do not need day‐to‐day calibration but all PEF meters should be replaced annually as with regular use the spring becomes slack and so the meter becomes inaccurate (NICE [137]).

All PEF meters should be used and maintained in accordance with the manufacturer's instructions. In settings where meters are used between patients, a log should be kept of cleaning and disinfection procedures, and disposable one‐way mouthpieces that prevent patients inhaling through the meter should be used (Hill and Winter [82]).

Spirometers

Spirometers can produce a reading for PEF alongside other lung function measurements such as FVC. However, to enable comparison with previous results, the patient should use the same equipment and technique each time (Dakin et al. [50]).

Assessment and recording tools

Recording peak flow measurements on individualized action plans or booklets gives patients a greater degree of control and awareness about when they need to access medical care; therefore, their use is strongly advocated (British Thoracic Society [30]).

Specific patient preparation

The procedure should be performed when the patient is at rest (unless otherwise specified) and may be performed with them sitting upright or standing as long as their neck is not flexed (NICE [137]). To increase reliability and enable comparisons to be drawn, it is advisable that the patient uses the same posture each time (Hill and Winter [82]).

Education

The practitioner must ensure that the patient is fully informed about how to perform the procedure and performs it accurately, as even small alterations in technique may produce inaccurate results (Bickley [18]). If the patient has not performed the procedure previously then they will need a full explanation of what PEF is, what it measures, and how they should interpret and act on the results (Hill and Winter [82]). Patients should have the opportunity to have the procedure demonstrated to them and have their own practice attempts (Peate and Wild [157]).

Procedure guideline 14.5

Peak flow reading using a manual peak flow meter

Table 14.8 Prevention and resolution (Procedure guideline 14.5)

Problem	Cause	Prevention	Action
Result is higher than expected	Needle was not being pushed back to zero prior to commencement Poor technique leading to ‘explosive decompression’ where there is sudden opening of the glottis, or release of the tongue occluding the mouthpiece; alternatively, the patient may be coughing or spitting into the mouthpiece ( Dakin et al. [50])	Allow practice runs prior to the procedure and ensure that the patient is educated on the correct technique.	Reset the needle back to zero. Educate the patient on the correct technique and, if they appear fatigued, allow them to rest prior to repeating the procedure.
Result is lower than expected	Failing to take a maximal inhalation Holding breath at maximal inhalation and delaying blowing into the meter Failure to make maximum effort Mouthpiece leaks due to blowing out cheeks, loose‐fitting dentures or facial palsy ( Hill and Winter [82])	As above.	As above.