Peak flow meter
Encyclopedia
The peak expiratory flow (PEF), also called peak expiratory flow rate (PEFR) is a person's maximum speed of expiration, as measured with a peak flow meter, 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.
First measure of precaution would be to check patient for signs and symptoms 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.
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.
There are a number of non-equivalent scales used in the measurement of Peak Flow.
Graphs or tables are available of predicted normal values based on a person's sex, age and height, and online calculators are available. There is a wide natural variation in results from healthy test subjects.
In 2004 the UK
switched from the original Wright scale to the newer, more accurate European scale. Wright values may be converted to the EU scale using the following formula:
The reverse calculation is:
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.
Peak flow readings are often classified into 3 zones of measurement according to the American Lung Association
; green, yellow, and red. Doctors and health practitioners can develop an asthma
management plan based on the green-yellow-red zones.
, 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.
Bronchus
A bronchus is a passage of airway in the respiratory tract that conducts air into the lungs. The bronchus branches into smaller tubes, which in turn become bronchioles....
and thus the degree of obstruction in the airways.
Function
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.First measure of precaution would be to check patient for signs and symptoms 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
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
.
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.
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.
Scales
Graphs or tables are available of predicted normal values based on a person's sex, age and height, and online calculators are available. There is a wide natural variation in results from healthy test subjects.
- Wright scale
- EN 13826 or EU scale
- A.T.S. (American Thoracic SocietyAmerican Thoracic SocietyAmerican Thoracic Society , established in 1905, is an independently incorporated, international, educational and scientific society, serving its 18,000 members worldwide who are dedicated in respiratory and critical care medicine...
) scale
In 2004 the UK
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
switched from the original Wright scale to the newer, more accurate European scale. Wright values may be converted to the EU scale using the following formula:
The reverse calculation is:
Measurement
The highest of three readings is used as the recorded value of the Peak Expiratory Flow Rate. It may be plotted out on graph paperGraph paper
Graph paper, graphing paper, grid paper or millimeter paper is writing paper that is printed with fine lines making up a regular grid. The lines are often used as guides for plotting mathematical functions or experimental data and drawing diagrams. It is commonly found in mathematics and...
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.
Peak flow readings are often classified into 3 zones of measurement according to the American Lung Association
American Lung Association
The American Lung Association is a voluntary health organization whose mission is to save lives by improving lung health and preventing lung disease.-History:...
; green, yellow, and red. Doctors and health practitioners can develop an asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
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 Asthma Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath... is under good control. |
| Yellow Zone | 50 to 79 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 Medical emergency A medical emergency is an injury or illness that is acute and poses an immediate risk to a person's life or long term health. These emergencies may require assistance from another person, who should ideally be suitably qualified to do so, although some of these emergencies can be dealt with by the... . Severe airway Airway The pulmonary airway comprises those parts of the respiratory system through which air flows, conceptually beginning at the nose and mouth, and terminating in the alveoli... narrowing may be occurring and immediate action needs to be taken. This would usually involve contacting a doctor or hospital. |
History
The measurement of peak expiratory flow was pioneered by Martin WrightMartin Wright (bioengineer)
Basil Martin Wright was a British bioengineer who invented several notable medical instruments, including the peak flow meter and Graseby syringe driver.- References :...
, 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.
See also
- SpirometrySpirometrySpirometry is the most common of the pulmonary function tests , measuring lung function, specifically the measurement of the amount and/or speed of air that can be inhaled and exhaled...
- Metered dose inhalerMetered dose inhalerA metered-dose inhaler is a device that delivers a specific amount of medication to the airway and lungs, in the form of a short burst of aerosolized medicine that is inhaled by the patient. It is the most commonly used delivery system for treating asthma, chronic obstructive pulmonary disease ...
- SalbutamolSalbutamolSalbutamol or albuterol is a short-acting β2-adrenergic receptor agonist used for the relief of bronchospasm in conditions such as asthma and chronic obstructive pulmonary disease. It is marketed as Ventolin among other brand names....
- Chronic obstructive pulmonary diseaseChronic obstructive pulmonary diseaseChronic obstructive pulmonary disease , also known as chronic obstructive lung disease , chronic obstructive airway disease , chronic airflow limitation and chronic obstructive respiratory disease , is the co-occurrence of chronic bronchitis and emphysema, a pair of commonly co-existing diseases...
(COPD) - AsthmaAsthmaAsthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
- Respiratory monitoringRespiratory monitoringMonitoring a patient's respiratory status usually takes place in a hospital setting and may be the primary purpose for a patient being observed or admitted to a medical setting....