(Peak Flow Meter, PFM, Peak Expiratory Flow Measurement)
Peak flow measurement is a procedure in which air flowing out of the lungs is measured. The measurement obtained is called the peak expiratory flow rate (PEFR), or peak expiratory flow (PEF).
Peak flow measurement may be obtained using a spirometer, an instrument with a mouth piece that measures the amount of air breathed in and/or out and the rate at which the air is inhaled and expelled from the lungs. Peak flow may also be measured with a peak flow meter (PFM), a portable, hand-held device. Both devices take the measurement as an individual forcefully blows into the mouthpiece of the device.
Spirometry is usually performed in a doctor’s office, clinic, or a hospital. A peak flow meter is small and light enough to be used almost anywhere. There are several types of PFMs available. However, it is important that one continues to use the same type of PFM on a consistent basis, as the PEFR can vary among different brands and types of meters.
Peak flow measurement using a peak flow meter is particularly useful for individuals with asthma. During an asthma flare-up, the large airways in the lungs slowly begin to narrow. This slows the speed of air leaving the lungs. A peak flow meter, when used properly, can reveal narrowing of the airways well in advanced of an asthma attack. Peak flow meters can help determine:
Other related procedures that may be used to diagnose problems of the lungs and respiratory tract include chest X-rays, bronchoscopy, bronchography, chest fluoroscopy, chest ultrasound, lung biopsy, lung scan, mediastinoscopy, oximetry, positron emission tomography (PET scan), pleural biopsy, pulmonary angiogram, pulmonary function tests, sinus X-ray, and thoracentesis. Please see these procedures for additional information.
The respiratory system is made up of the organs involved in the exchange of gases, and consists of the:
The upper respiratory tract includes the:
The lower respiratory tract includes the lungs, bronchi, and alveoli.
The lungs take in oxygen, which cells need to live and carry out their normal functions. The lungs also get rid of carbon dioxide, a waste product of the body's cells.
The lungs are a pair of cone-shaped organs made up of spongy, pinkish-gray tissue. They take up most of the space in the chest, or the thorax (the part of the body between the base of the neck and diaphragm).
The lungs are enveloped in a membrane called the pleura.
The lungs are separated from each other by the mediastinum, an area that contains the following:
The right lung has three sections called lobes. The left lung has two lobes. When you breathe, the air enters the body through the nose or the mouth. It then travels down the throat through the larynx (voice box) and trachea (windpipe) and goes into the lungs through tubes called mainstem bronchi.
One mainstem bronchus leads to the right lung and one to the left lung. In the lungs, the mainstem bronchi divide into smaller bronchi and then into even smaller tubes called bronchioles. Bronchioles end in tiny air sacs called alveoli.
A peak flow meter (PFM) can assist with the management of asthma. It can provide you and your doctor with information about how open the airways are in your lungs. The PFM can detect small changes in the large airways before you start to wheeze.
Using a PFM every day will let you know when your peak flows are starting to drop. This allows you to make early changes in your medication or routine to help prevent asthma symptoms from worsening. The PFM can also identify the value at which you will need to call your doctor or go to the emergency room.
Peak flow meters are primarily used for individuals who have asthma. Your doctor may not recommend that a PFM be used unless your asthma is considered moderate or severe and you are managed with medication(s). Peak flow meters are also useful in children who have asthma.
The measurements obtained by PFMs may also be useful in evaluating other conditions such as:
Because obtaining peak flow measurement is a noninvasive procedure, it is safe for most individuals. It is quick and inexpensive. However, the individual must be able to follow clear, simple directions.
Having to take in deep breaths to perform the procedure may cause you to feel dizzy, light-headed, or short of breath.
The procedure may trigger coughing and/or wheezing.
There may be risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.
Certain factors or conditions may interfere with the accuracy of peak flow measurement. These factors may include, but are not limited to, the following:
Peak flow measurement may be performed one or more times daily at the same time of day, whenever you are experiencing early warning signs of an asthma attack, or as otherwise directed by your doctor. You should always use the PFM before taking asthma medication. Your doctor may recommend other times when using a PFM is useful.
Generally, peak flow measurement follows this process:
Any type of care after the procedure will be based on the results of the procedure. Your doctor will instruct you about your peak flow zones and how you should respond when your peak flow measurement indicates a particular zone.
Peak flow zones are based on the traffic light concept: red means danger, yellow means caution, and green means safe. These zones are different for each person. Your doctor will help determine your peak flow zones. The three peak flow zones include:
The goal of the peak flow zones is to recognize early symptoms of uncontrolled asthma.
If it is necessary for you to get a new PFM, you should obtain a new personal best value for the new meter.
Your doctor may give you additional or alternate instructions depending on your particular situation.
The content provided here is for informational purposes only, and was not designed to diagnose or treat a health problem or disease, or replace the professional medical advice you receive from your doctor. Please consult your health care provider with any questions or concerns you may have regarding your condition.
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