peak flow meter: Definition from Answers.com

A peak flow meter issued in the UK.

A peak flow meter is a small, hand-held device used to monitor a person's ability to breathe out air. It measures the airflow through the bronchi and thus the degree of obstruction in the airways.

1 Function
2 Scales
3 Measurement
4 See also
5 References

Function

A peak flow meter measures the patient's maximum speed of expiration, or peak expiratory flow rate (PEFR or PEF). Peak flow readings are higher when patients are well, and lower when the airways are constricted. From changes in recorded values, patients and doctors may determine lung functionality, severity of asthma symptoms, and treatment options.

The measurement of peak expiratory flow was pioneered by Dr. Martin Wright, who produced the first meter specifically designed to measure this index of lung function. Since the original design of instrument was introduced in the late 1950s, and the subsequent development of a more portable, lower cost version (the 'Mini-Wright' peak flow meter), other designs and copies have become available across the world.

First measure of precaution would be to check patient for signs and syptoms of asthmatic hypervolemia. This would indicate whether or not to even continue with the Peak Flow Meter procedure. Measurement of PEFR requires training to correctly use a meter and the normal expected value depends on a patient's sex, age and height. It is classically reduced in obstructive lung disorders such as asthma.

Due to the wide range of ‘normal' values and high degree of variability, peak flow is not the recommended test to identify asthma. However, it can be useful in some circumstances.

A small proportion of people with asthma may benefit from regular peak flow monitoring. When monitoring is recommended, it is usually done in addition to reviewing asthma symptoms and frequency of reliever medication use.^[1]

When peak flow is being monitored regularly, the results may be recorded on a peak flow chart.

It is important to use the same peak flow meter every time.

Peak flow monitoring is not recommended for children under 12 years.

Scales

This peak flow meter uses the EU scale.

The Wikibook Medical Equipment has a page on the topic of

Peak Flow Meter

There are a number of non-equivalent scales used in the measurement of Peak Flow.^[2]

Graphs or tables are available of predicted normal values based on a person's sex, age and height. It should be noted that there is a wide natural variation in results from healthy test subjects.

Wright scale^[3]^[4]
EN 13826 or EU scale^[5]
A.T.S. (American Thoracic Society) scale

In 2004 the UK switched from the original Wright scale to the newer, more accurate European scale. Limited information on converting between the scales exists.^[6]

Measurement

The best of three readings is used as the recorded value of the Peak Expiratory Flow Rate. It may be plotted out on graph paper charts together with a record of symptoms or using peak flow charting software. This allows patients to self-monitor and pass information back to their doctor or nurse.^[7]

Peak flow readings are often classified into 3 zones of measurement according to the American Lung Association^[8]; green, yellow, and red. Doctors and health practitioners can develop an asthma management plan based on the green-yellow-red zones.

Zone	Reading	Description
Green Zone	80 to 100 percent of the usual or normal peak flow readings are clear.	A peak flow reading in the green zone indicates that the asthma is under good control.
Yellow Zone	50 to 80 percent of the usual or normal peak flow readings	Indicates caution. It may mean respiratory airways are narrowing and additional medication may be required.
Red Zone	Less than 50 percent of the usual or normal peak flow readings	Indicates a medical emergency. Severe airway narrowing may be occurring and immediate action needs to be taken. This would usually involve contacting a doctor or hospital.

References

^ National Asthma Council of Australia
^ Martin R. Miller (June 2004). "Peak expiratory flow meter scale changes: implications for patients and health professionals" (PDF). The Airways Journal 2 (2): 80. http://www.airwaysextra.com/AJJune2004-Miller-published.pdf. Retrieved 2006-06-06.
^ Nunn A, Gregg I (1989). "New regression equations for predicting peak expiratory flow in adults". BMJ 298 (6680): 1068–70. PMID 2497892. - Predicted peak expiratory flow in normal adults using Wright-scale
^ Godfrey S, Kamburoff PL, Naim JL (1970). "Spirometry, lung volumes and airway resistance in normal children ages 5 to 18". Br J Dis Chest 64: 15–24. doi:10.1016/S0007-0971(70)80045-6. - Predicted peak expiratory flow in normal children using Wright-scale
^ Clement Clarke International (2004). "Predictive Normal Values (Nomogram, EU scale)". Clement Clarke International. http://www.peakflow.com/top_nav/normal_values/index.html. Retrieved 2006-06-06. - Downloadable PDF charts for adults and children using EU scale
^ Clement Clarke International (2004). "Mini-Wright Peak Flow Meter - Wright to EU (EN13826) converter" (EXE macromedia flash). Clement Clarke International. http://www.mortonmedical.co.uk/PEFscale.exe. Retrieved 2006-06-06.
^ Scottish Intercollegiate Guidelines Network & The British Thoracic Society (2003). "British Guideline on the Management of Asthma - Annex 8: Personal Asthma Action Plan" (PDF). Thorax 58: Suppl I. http://www.enterpriseportal2.co.uk/filestore/bts/annex8asthma05.pdf. Retrieved 2006-06-06. - for recording chart of PEFR readings
^ American Lung Association. "How can I determine a normal peak flow rate for me?". http://www.lungusa.org/site/pp.asp?c=dvLUK9O0E&b=22586.

v • d • e Respiratory system, physiology: respiratory physiology

Lung volumes	VC · FRC · Vt · dead space · CC calculations: respiratory minute volume · FEV1/FVC ratio devices: spirometry · body plethysmography · peak flow meter

Airways/ ventilation (V)	positive pressure ventilation · breath (inhalation, exhalation) · respiratory rate · respirometer · pulmonary surfactant · compliance · hysteresivity · airway resistance · bronchial hyperresponsiveness · bronchial challenge test · bronchoconstriction/bronchodilation

Blood/ perfusion (Q)	pulmonary circulation · hypoxic pulmonary vasoconstriction · pulmonary shunt

Interactions/ ventilation/perfusion ratio (V/Q)	ventilation/perfusion scan · zones of the lung · gas exchange · pulmonary gas pressures · alveolar gas equation · alveolar-arterial gradient · hemoglobin · oxygen-haemoglobin dissociation curve (2,3-DPG, Bohr effect, Haldane effect) · carbonic anhydrase (chloride shift) · oxyhemoglobin · respiratory quotient · arterial blood gas · diffusion capacity (DLCO)

Control of respiration	pons (pneumotaxic center, apneustic center) · medulla (dorsal respiratory group, ventral respiratory group) · chemoreceptors (central, peripheral) · pulmonary stretch receptors (Hering-Breuer reflex)

Insufficiency	high altitude · oxygen toxicity · hypoxia

respiratory system navs: anat nose,larynx/lower+thoracic cavity/physio/dev, noncongen/congen/tumors, symptoms+signs/eponymous, proc

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peak flow meter

Contents

Function

Scales

Measurement

See also

References