Peak flow meter 1834834 224144690 2008-07-07T14:55:44Z 90.240.96.154 [[Image:Peak flow meter horiz.jpg|thumb|200px|right|A peak flow meter issued in the UK.]] A '''peak flow meter''' is a small, hand-held device used to manage [[asthma]] by monitoring airflow through the [[bronchus|bronchi]] and thus the degree of obstruction in the airways. ==Function== The peak flow meter measures the patient's maximum ability to exhale, 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 [[Martin Wright (bioengineer)|Dr. Basil 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. 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]]. == Scales == [[Image:Peak flow meter vert.jpg|thumb|200px|right|This peak flow meter uses the EU scale.]] There are a number of non-equivalent scales used in the measurement of Peak Flow.<!-- --><ref name="Airways2004-Miller">{{cite journal | author = Martin R. Miller | year = 2004 | month = June | title = Peak expiratory flow meter scale changes: implications for patients and health professionals | journal = The Airways Journal | volume = 2 | issue = 2 | pages = 80 | url = http://www.airwaysextra.com/AJJune2004-Miller-published.pdf | format = PDF | accessdate = 2006-06-06}}</ref> Graphs or tables are available of predicted normal values based on a person's gender, age and height. It should be noted that there is a wide natural variation in results from healthy test subjects. * ''Wright'' scale<!-- --><ref name="NormalAdults-WrightScale">{{cite journal | author=Nunn A, Gregg I | title=New regression equations for predicting peak expiratory flow in adults | journal=BMJ | volume=298 | issue=6680 | pages=1068–70 | year=1989 | pmid=2497892}} - Predicted peak expiratory flow in normal adults using Wright-scale</ref><!-- --><ref name="NormalChildren-WrightScale">{{cite journal | author = Godfrey S, Kamburoff PL, Naim JL | year = 1970 | title = Spirometry, lung volumes and airway resistance in normal children ages 5 to 18 | journal = Br J Dis Chest | volume = 64 | pages = 15–24 | doi = 10.1016/S0007-0971(70)80045-6}} - Predicted peak expiratory flow in normal children using Wright-scale</ref> * ''EN 13826'' or EU scale<!-- --><ref name="Adults-Children-EUscale">{{cite web | author =Clement Clarke International | year=2004 | url=http://www.peakflow.com/top_nav/normal_values/index.html | title =Predictive Normal Values (Nomogram, EU scale) | publisher =Clement Clarke International | accessdate =2006-06-06}} - Downloadable PDF charts for adults and children using EU scale</ref> * ''A.T.S.'' ([[American Thoracic Society]]) scale In 2004 the [[United Kingdom|UK]] switched from the original Wright scale to the newer, more accurate European scale. Limited information on converting between the scales exists.<!-- --><ref name="CC-scale-conv">{{cite web | author=Clement Clarke International | year = 2004 | url=http://www.mortonmedical.co.uk/PEFscale.exe | title =Mini-Wright Peak Flow Meter - Wright to EU (EN13826) converter | format =EXE macromedia flash | publisher =Clement Clarke International | accessdate =2006-06-06}}</ref> == Measurement == {{Wikibookspar|Transwiki|Peak flow meter}} 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.<ref>{{cite website| title=Peak flow charting software| url=http://www.my-peak-flow.com/peak-flow-info.html}}</ref> This allows patients to self-monitor and pass information back to their doctor or nurse.<!-- --><ref name="SIGN2003-Annex8">{{cite journal | author = Scottish Intercollegiate Guidelines Network & The British Thoracic Society | year = 2003 | title = British Guideline on the Management of Asthma - Annex 8: Personal Asthma Action Plan | journal = Thorax | volume = 58 | pages = Suppl I | url = http://www.enterpriseportal2.co.uk/filestore/bts/annex8asthma05.pdf | format = PDF | accessdate=2006-06-06}} - for recording chart of PEFR readings</ref> Peak flow readings are often classified into 3 zones of measurement according to the [[American Lung Association]]<ref>{{cite website| title=How can I determine a normal peak flow rate for me?| author=American Lung Association| url=http://www.lungusa.org/site/pp.asp?c=dvLUK9O0E&b=22586}}</ref>; green, yellow, and red. The color system is based on the colors of street [[traffic lights]]. Doctors and health practitioners can develop an [[asthma]] management plan based on the green-yellow-red zones. The Green Zone means 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. The Yellow Zone means 50 to 80 percent of the usual or normal peak flow readings indicate caution. It may mean respiratory [[airways]] are narrowing and additional medication may be required. The Red Zone means less than 50 percent of the usual or normal peak flow readings indicate 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. == See also == * [[Spirometry]] * [[Metered dose inhaler]] * [[Asthma inhalers]] * [[Salbutamol]] * [[COPD]] * [[DOG]] == References == {{reflist}} [[Category:Flow meters]] [[Category:Medical equipment]] [[Category:Respiratory therapy]] [[Category:Asthma]] [[no:PEF-måler]] [[sv:Topputandningsflöde]]