Keeping track of your peak flow rate might be part of your asthma action plan. Learn how these devices work and the right way to use one.
Is your asthma as well-controlled as it should be? Are you in danger of having a flare-up? To answer these questions, the American Lung Association recommends monitoring your asthma symptoms daily, and there are several ways to do that. One option is to use a peak flow meter, a simple handheld device that measures how well you can push air out of your lungs. Stainless Steel Ultrasonic Water Meter
“We ask some of our asthmatics to use [peak flow meters] so we can tell if their asthma is flaring or if they’re headed for an asthma attack,” says Purvi Parikh, M.D., an allergist and immunologist at NYU Langone Health in New York City.
A peak flow meter measures your peak expiratory flow (PEF), which refers to how great a volume of air, as measured in liters, you can forcefully exhale in one blast, according to the University of Glasgow.
A pro of peak flow meters is that they are small, portable, and easy to use. In addition, monitoring your PEF with a peak flow meter—at least in the short term—can be useful for establishing a baseline for your personal asthma action plan (more on these below), according to the most recent guidelines from the Global Initiative for Asthma (GINA). It may also help you and your doctor assess how you’re responding to treatment and identify triggers for flares.
There are also downsides. For one, they’re not very accurate, says Angela Duff Hogan, M.D., a pediatric allergist and immunologist in Norfolk, VA, and vice chair of the American College of Allergy, Asthma and Immunology’s (ACAAI) asthma committee. “It’s like measuring your height by using a yardstick that doesn’t have any markings on it,” she says. “It’s a very crude measurement.”
Additionally, Dr. Hogan notes that peak flow meters are effort-dependent and therefore easy to manipulate. “If you don’t put forth a good effort, you don’t get a good value,” she says.
Not everyone with asthma needs to use a peak flow meter. The American Lung Association notes that not all healthcare providers recommend these devices and that they are unlikely to be helpful for people with mild asthma. In fact, the latest GINA guidelines note that long-term monitoring of PEF with a peak flow meter is “now generally only recommended for patients with severe asthma, or those with impaired perception of airway limitation.”
Dr. Parikh says that if you have moderate or severe asthma, or if you suspect that your asthma might be flaring but aren’t sure, a peak flow meter might be useful.
In a perfect world, someone who needs good feedback about their asthma would be measuring FEV1—or forced expiratory volume in 1 second—instead of measuring PEF with a peak flow meter, say Dr. Parikh and Dr. Hogan. They note that FEV1 is a more useful and precise measurement, but FEV1 must be measured with a spirometer, which is more expensive and not as widely accessible. Additionally, research has found that FEV1 is not necessarily more accurate than PEF when measured with a portable device by a patient, as opposed to at a doctor’s office.
The best way to know whether you would benefit from using a peak flow meter at home? Simply ask your doctor, says Dr. Hogan. If your asthma is severe, your doctor might instead advise using a spirometer that checks FEV1, she says. For many people, a better way to measure asthma control is to simply assess how they’re feeling and functioning, according to the American Lung Association, which cites Baylor College of Medicine’s Rules of Two as an easy method for doing this. You ask yourself these questions:
Do you have asthma symptoms or use your quick-relief inhaler more than two times per week?
Do you wake up at night with symptoms more than two times per month?
Do you need to refill your quick-relief inhaler more than two times per year?
If you answer yes to one or more of these questions, your asthma may not be well-controlled, and you should speak with your doctor.
To use a peak flow meter, take a deep breath, put your mouth around the mouthpiece, and exhale as hard as you can, says Dr. Parikh. The American Lung Association provides these specific steps:
Check to see that the arrow/marker on your meter is at zero (or the lowest number visible).
Stand up straight, take as deep a breath as possible, and put the mouthpiece into your mouth. Close your lips tightly, keep your tongue away from the mouthpiece, and blow out as hard and fast as you can in one big blast.
Look to see where the arrow/marker has risen to and write down that number.
Repeat this process three times. If you’re doing it right, the numbers should be close together.
Record the highest of the three measurements (not the average).
If your doctor has advised you to use a peak flow meter, they should also tell you how often to test.
Not everyone with asthma has the same lung capacity, and factors like height and weight also play a role, according to the Asthma and Allergy Foundation of America (AAFA). That’s why, if your doctor has advised you to use a peak flow meter, it’s important to know what your personal best peak flow, or PEF, number is. You should do this when you aren’t sick and don’t have any asthma symptoms, says Dr. Parikh.
To determine your personal best peak flow, per the AAFA:
Measure your peak flow at least twice a day for two to three weeks.
Do the test when you wake up and again between 12 p.m. and 2 p.m.
The highest number you get over this period is your personal best peak flow.
Whether you regularly measure your peak flow or not, an asthma action plan is “the single most important tool an asthmatic should have,” says Dr. Hogan. In short, it’s a simple guide that tells you how to manage your asthma and what to do if your symptoms start to worsen.
The AAFA , American Lung Association , and CDC all have downloadable plans on their websites that you can print out and fill in with the help of your doctor. The exact format of the plan may vary, but most asthma action plans are divided into green (go/normal), yellow (caution), and red (danger) zones:
This means you don’t have any noticeable symptoms and are feeling fine. If you use a peak flow meter, your reading will be more than 80% of your personal best. You may or may not be taking daily maintenance medication.
You have some symptoms, such as mild coughing or wheezing. If you use a peak flow meter, your reading is between 50% and 79% of your personal best. Your doctor will likely advise you to use your quick-relief medication when you’re in this zone.
You have significant symptoms and trouble breathing, and your quick-relief medication isn’t helping. If you use a peak flow meter, your reading is less than 50% of your personal best. Your doctor should give you specific instructions for what to do in this circumstance, which may include taking additional quick-relief medication. The American Lung Association notes that you should call 911 if you’re still in the red zone after 15 minutes, have trouble walking or talking because of your shortness of breath, or if your lips or fingernails are blue.
A peak flow meter is one way to measure how well controlled your asthma is. If your doctor recommends using one, be sure you understand how to use it, how to determine your personal best peak flow, and how often to test. Whether you regularly measure your peak flow or not, you should have an asthma action plan that tells you how to manage your condition and what to do if your symptoms worsen.
Monitoring Asthma Symptoms: American Lung Association. (2022.) “Assess and Monitor Your Asthma Control.” https://www.lung.org/lung-health-diseases/lung-disease-lookup/asthma/managing-asthma/asthma-control
What a Peak Flow Meter Measures: University of Glasgow School of Medicine, Dentistry, and Nursing. (n.d.) “Peak Expiratory Flow Rate.” https://www.gla.ac.uk/media/Media_678202_smxx.pdf
Usefulness of Peak Flow Meters vs. FEV1: Global Initiative for Asthma. (2023.) “Global Strategy for Asthma Management and Prevention.” https://ginasthma.org/wp-content/uploads/2023/07/GINA-2023-Full-report-23_07_06-WMS.pdf
Real-World Accuracy of FEV1 and PEF Measurements: NPG Primary Care Respiratory Medicine. (2017.) “Peak Flow Meter With a Questionnaire and Mini-Spirometer to Help Detect Asthma and COPD in Real-Life Clinical Practice: A Cross-Sectional Study.” https://pubmed.ncbi.nlm.nih.gov/28487516/
How to Use Peak Flow Meter: American Lung Association. (2023.) “Measuring Your Peak Flow Rate.” https://www.lung.org/lung-health-diseases/lung-disease-lookup/asthma/treatment/devices/peak-flow
Personal Best Peak Flow: Asthma & Allergy Foundation of America. (2017.) “Peak Flow Meters.” https://aafa.org/asthma/asthma-diagnosis/lung-function-tests-diagnose-asthma/peak-flow-meters
AAFA Asthma Action Plan: Asthma & Allergy Foundation of America. (2015.) “Asthma Action Plan.” https://aafa.org/asthma/asthma-treatment/asthma-treatment-action-plan/
American Lung Association Asthma Action Plan: American Lung Association. (2022.) “My Asthma Action Plan.” https://www.lung.org/getmedia/dc79f142-a963-47bc-8337-afe3c3e87734/FY22-ALA-Asthma-Action-Plan-with-QR-codes.pdf
Monitoring Asthma Symptoms: American Lung Association. (2022.) “Assess and Monitor Your Asthma Control.” https://www.lung.org/lung-health-diseases/lung-disease-lookup/asthma/managing-asthma/asthma-control
What a Peak Flow Meter Measures: University of Glasgow School of Medicine, Dentistry, and Nursing. (n.d.) “Peak Expiratory Flow Rate.” https://www.gla.ac.uk/media/Media_678202_smxx.pdf
Usefulness of Peak Flow Meters vs. FEV1: Global Initiative for Asthma. (2023.) “Global Strategy for Asthma Management and Prevention.” https://ginasthma.org/wp-content/uploads/2023/07/GINA-2023-Full-report-23_07_06-WMS.pdf
Real-World Accuracy of FEV1 and PEF Measurements: NPG Primary Care Respiratory Medicine. (2017.) “Peak Flow Meter With a Questionnaire and Mini-Spirometer to Help Detect Asthma and COPD in Real-Life Clinical Practice: A Cross-Sectional Study.” https://pubmed.ncbi.nlm.nih.gov/28487516/
How to Use Peak Flow Meter: American Lung Association. (2023.) “Measuring Your Peak Flow Rate.” https://www.lung.org/lung-health-diseases/lung-disease-lookup/asthma/treatment/devices/peak-flow
Personal Best Peak Flow: Asthma & Allergy Foundation of America. (2017.) “Peak Flow Meters.” https://aafa.org/asthma/asthma-diagnosis/lung-function-tests-diagnose-asthma/peak-flow-meters
AAFA Asthma Action Plan: Asthma & Allergy Foundation of America. (2015.) “Asthma Action Plan.” https://aafa.org/asthma/asthma-treatment/asthma-treatment-action-plan/
Garden Hose Water Meter American Lung Association Asthma Action Plan: American Lung Association. (2022.) “My Asthma Action Plan.” https://www.lung.org/getmedia/dc79f142-a963-47bc-8337-afe3c3e87734/FY22-ALA-Asthma-Action-Plan-with-QR-codes.pdf