A peak flow meter (PFM) is a device used to measure how well your child's asthma is under control. The device measures air flowing out of the lungs, called peak expiratory flow rate (PEFR), as a child with asthma forcefully blows into the device. A peak flow meter, when used properly, can reveal narrowing of the airways well in advance of an asthma attack. As part of your asthma care plan, peak flow meters can help determine:
The PFM removes a lot of guesswork out of managing your child's asthma. It can provide you, your child's doctor, or even the school teachers with information about how open the airways are in your child's lungs.
The PFM can detect small changes in the large airways before your child starts to wheeze. Using a PFM every day will let you know when your child's peak flows are starting to drop. This allows you to make early changes in your child's medication or routine to help prevent your child's asthma symptoms from getting worse. The PFM can also identify the value at which you will need to call your child's doctor or go to the emergency room.
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 child's doctor will help determine your child's peak flow zones. The three peak flow zones include:
The goal of the peak flow zones is to help you recognize when the asthma may start to become uncontrolled. The goal is to stay within the 80 percent value of your personal best peak flow measurement. Zones with a smaller range, such as 90 to 100 percent, may be recommended by some health care providers. Always follow the advice of your doctor regarding the peak flow rate.
Each child's peak flow zones are based on his or her personal best peak flow number. To establish your child's personal best peak flow, have your child take his or her peak flow measurement each day at the same time for two to three weeks, when the asthma is under control.
After recording your child's peak flow measurements for two to three weeks consistently, your child's doctor may also measure the optimum lung function with a spirometer (a device that can check lung function by measuring both the amount of air expelled and how quickly the air was expelled). The spirometer measurement may then be compared with the peak flow meter record to help set up an asthma management and treatment plan.
Your child's personal best peak flow measurement may change over time. Consult your child's doctor as to when to check for a new personal best peak flow measurement.
Peak flow meters should be used regularly to check how well the asthma is being controlled. In addition, the peak flow meter may be a valuable tool during an asthma attack, because it can help determine how well the short-term, quick-relief asthma medication is working. The National Heart, Lung, and Blood Institute (NHLBI) recommends measuring lung function during the following times:
The peak flow meter is a tool to help collect information. The key to successful asthma management is communicating this information (the peak flow meter recordings, the severity of your child's symptoms, and the effectiveness of your child's medications) to your child's doctor.
Consult your child's doctor about obtaining a peak flow meter and for step-by-step instructions on how to use the device.
If you are using more than one peak flow meter, be sure they are the same brand.
An oximeter is a small machine that measures oxygen saturation (the amount of oxygen) in your child's blood.
To get this measurement, a small sensor (similar to an adhesive bandage) is taped onto your child's finger or toe. When the oximeter is on, a small red light can be seen in the sensor. The sensor is painless and the red light does not get hot.
A spirometer is a device used by your child's doctor that assesses lung function. Spirometry, the evaluation of lung function with a spirometer, is one of the simplest, most common pulmonary function tests and may be necessary for any of the following reasons:
After taking a deep breath, your child forcefully breathes out into the spirometer as completely and forcefully as possible. The spirometer measures both the amount of air expelled and how quickly the air was expelled from the lungs. The measurements are recorded by the spirometer.
The normal, healthy values measured by the spirometer for the amount of air exhaled vary from child to child. Your results are compared to the average expected in someone of the same age, height, sex, and race, according to NHLBI. However, if the values fall below 85 percent of the average, it may indicate a lung disease or other airflow obstruction. If a child has abnormal spirometer measurements, he/she may be referred for other lung tests to establish a diagnosis.
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Online Resources of Respiratory Disorders