How to use a peak flow meter to monitor your asthma or COPD
- You use a peak flow meter by standing up straight and blowing as hard as you can into the handheld device.
- A peak flow meter is primarily used by people who have lung conditions like COPD and asthma.
- It measures your airflow rate and can help you monitor the state of your lungs.
- This article was medically reviewed by Osita Onugha, MD, thoracic surgeon and assistant professor of thoracic surgical oncology at John Wayne Cancer Institute at Providence Saint John's Health Center in Santa Monica, California.
A peak flow meter is a device that measures how well your lungs expel air. The device is a valuable tool for people with a respiratory condition like asthma or COPD, because it helps track the condition and stay on top of their overall health. Here's what you need to know about how to use a peak flow meter to know if your respiratory condition is worsening.
What a peak flow meter can tell you
Peak flow meters are inexpensive (the average price is around $15 to $20), handheld, and easy to use. You simply blow as hard as you can into the device and it will measure your air flow rate in liters per minute (L/Min).
Peak flow meters are typically helpful for people with obstructive lung conditions, such as asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis. These conditions can result in reduced airflow out of the lungs and difficulty fully exhaling.
Your doctor will let you know if you can benefit from using one, as well as how to read your results. Instructions will vary, but it's common for a doctor to recommend measuring your peak flow levels twice a day.
Keeping track of your peak flow levels can help you:
- Assess how well your current treatment/medication is working.
- Know when to call your doctor or in serious cases, get emergency care.
- Track asthma over time and determine if it's worsening or improving.
- Identify flare-ups
Peak flow meters are especially helpful for people who are "poor perceivers," meaning that they have trouble identifying the signs of a worsening lung condition without a clear metric. It's especially important for these people to use their peak flow meters regularly, says Atul Malhotra MD, Research Chief of Pulmonary, Critical Care, and Sleep Medicine at UC San Diego Health.
Otherwise, a poor receiver may not notice if their condition is worsening and it could lead to episodes of difficulty breathing like an asthma attack.
Getting a low peak flow reading can indicate that your condition is worsening or that your airways are narrowing.
How to find your personal best peak flow number
Before you start regularly tracking your peak flow meter scores, you want to establish a baseline peak flow reading that represents normal lung function. Your doctor may want to work with you to come up with this number, but you can also find it yourself.
To find your personal best peak flow reading, keep track of your peak flow scores over a two-to-three week period. You should do this during a time when your lungs are functioning properly and you are not experiencing any flare-ups of your respiratory condition. Your personal best peak flow reading is the highest number you achieve during this two-to-three week period.
How to use a peak flow meter:
The best time to take your peak flow levels is in the morning before you take your asthma medications. But if you are having more lung trouble than usual, you may have to use the device more often. Ask your doctor how often many times a day you should use your peak flow meter.
- Start fresh by sliding the arrow marker to zero, or the base of the scale.
- Stand up straight.
- Take the deepest breath you can.
- Place the mouthpiece in your mouth and seal your lips around it.
- Breathe out with maximum effort, as hard and fast as you can, until you've run out of air in your lungs and can't breathe out anymore.
- Write down the value that you score for L/Min.
- Repeat steps one through six two more times, so you have a total of three readings.
- Use the highest of the three readings as your PF score, and take note of that in your asthma (or COPD or CF) diary. The Asthma Initiative of Michigan has a useful template for how to track PF scores, which you can download here.
It's important to keep track of your scores so you know what's normal for you. Malhotra says this is crucial so you know if you need to use your inhaler, nebulizer, or call your doctor to get urgent assistance if you are scoring a low peak flow score.
Green, yellow, and red zones
Some doctors will refer to different colored zones when working with a patient who uses a peak flow meter. According to the American Lung Association, here are what the three zones are and what they mean:
- Green: This means that your peak flow score is 80-100% of your personal best score. Scoring in the green zone is good, and you should continue with your normal day-to-day treatments. There is no cause for concern.
- Yellow: Yellow is when you're at 50-80% of your personal best score, indicating that you should move forward with caution. This could possibly mean that your condition is worsening and that you may need to use your rescue medication, like an inhaler. However, this is not always the case. Your plan when you're in the yellow zone may differ person to person –– it's based on whatever your provider tells you is necessary at this level.
- Red: Red means that action needs to be taken ASAP, because your peak flow score is below 50% of your personal best score. Again, you and your provider should have a plan for what the red zone personally means for you and what actions you need to take if you score this low.
Your doctor can help you figure out what the values would be for each of these zones so there is no confusion. Regardless of using color zones or not, your doctor can let you know what scores would definitely be a cause of alarm for you.
"The bottom line is that if the peak flow falls to a certain level, as determined by the patient talking to their doctor, they should call their doctor or go to the emergency room. Again the numbers vary for each individual so important to have that conversation [with your provider]," says Malhotra. This way, you will always know what to do in the case of an emergency, and it's always better to be safe than sorry.
A peak flow meter isn't the only way to track and control your condition. You can also use a symptom diary, if you aren't a poor perceiver. Additionally, you should have a good long-term relationship with your pulmonologist and an ongoing treatment plan that may include a variety of medications and medication delivery devices such as inhalers or nebulizers.