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Peak flow meters are portable devices that are easy to use at home, in school, or on the go. They’re used to measure a person’s ability to exhale air forcefully out of their lungs.

If you have a respiratory condition, such as asthma or chronic obstructive pulmonary disease (COPD), your doctor may recommend you use a peak flow meter as part of your treatment routine.

They’re usually used by people with asthma to measure peak expiratory flow rate (PEFR or peak flow). PEFR is the maximum speed you’re able to use when blowing air out of your lungs.

Your doctor may recommend using a peak flow meter daily or several times a day, as part of a personalized asthma action plan for managing symptoms.

Peak flow meters have a mouthpiece you forcefully blow into with one powerful breath. The meter measures the force you expel air in liters per minute (L/m). An indicator on the meter moves in response to the force of your breath to a spot along a numbered scale.

Consistent use of a peak flow meter can help you keep track of how well asthma is being controlled. It can also help signal a change in a respiratory condition, such as COPD.

Keeping track of your readings can provide information that your asthma is getting worse or that a flare is coming. If your numbers decline, it can alert you that your airways have narrowed before you have asthmatic symptoms.

A peak flow meter can also help you and your doctor determine if your current treatment protocol is effective or needs to be changed.

Can my young child use a peak flow meter?

Children as young as 4 or 5 may be able to use a peak flow meter, if they’re at least 43 inches tall.

Peak flow meters provide information that is used with peak flow rate charts or calculators. These charts give estimated information about peak flow zones, so you can determine if your child is in the green, yellow, or red zone for breathing. On peak flow charts, estimated personal best peak flow starts at 43 inches.

If your child is shorter than 43 inches, talk with their pediatrician about using of a peak flow meter and other options.

Can a peak flow meter help me identify asthma triggers in my environment?

Yes. By keeping a daily diary of your readings, you can identify triggers that may worsen asthma symptoms.

It helps if you keep a timed asthma diary of possible triggers you come into contact with, as well as daily activities which might trigger an asthma attack.

Do I need to wash my peak flow meter regularly?

Yes. An unwashed meter can harbor bacteria and germs.

To wash your meter, use mild soap and warm water. Some meters can be washed in the top rack of a dishwasher. Make sure your meter is completely dry before you use it.

There are two types of peak flow meters.

Digital peak flow meter

Digital peak flow meters provide two readings:

  • PEFR
  • forced expiratory volume (FEV1)

FEV1 is the amount of air you breathe out within one second of using the meter. Digital monitors let you download your readings to share with your doctor via email or text.

Mechanical peak flow meter

Mechanical meters only measure PEFR. Many come with charts you can fill in manually, to keep a record of your readings.

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Illustration by Bailey Mariner

Microlife PF100 Digital Peak Flow & FEV1 Meter

  • Price: $$$

Like all digital meters, this peak flow meter measures PEFR and FEV1.

It stores up to 240 readings, complete with date and time stamp. This meter will automatically track your highest readings, so you don’t have to input that information manually. A risk indicator lets you know when you’re in the yellow or red zone.

The meter comes with batteries and a carrying case.

Some reviewers mention that customer service from the company is lacking, and that complaints are not handled quickly.

Omron PF9940 PeakAir Peak Flow Meter

  • Price: $

This lightweight and portable mechanical meter has adjustable green, yellow, and red zone indicators. Like all mechanical meters, you’ll need to keep a written record or chart of your readings.

The mouthpiece is removable for hand washing.

Many reviewers mention that the meter is easy to use and accurate.

Philips Respironics Peak Flow Meter

  • Price: $$

This mechanical meter has a built-in handle for easy use. It has a range from 60 to 810 L/m.

A green/yellow zone lever and yellow/red zone lever let you set your own personal minimum and maximum air flow settings for easy indication during readings.

Mini-Wright Standard Range Peak Flow Meter

  • Price: $$

This mechanical meter has a standard range from 60 to 880 L/m. A built-in, one-way valve prevents inhaling through the device, assuring you of accurate readings.

The meter comes with a diary for easy recordings of readings.

It can be used with disposable mouthpieces, making it a viable tool for multiple users. If you use this meter for more than one person, make sure to clean it after each use.

This product comes with a 100 percent money-back guarantee and a 1-year limited manufacturer’s warranty. The manufacturer recommends automatic replacement every 3 years for single users, and more often for multiple users.

Mini-Wright AFS Low Range Peak Flow Meter

  • Price: $$

This mechanical peak flow meter is designed for people who can’t obtain a high PEFR. It takes readings from 30 to 400 L/m. You can use this meter alone or with a standard peak flow meter.

It has a built-in, one-way valve, and it can be used with disposable mouthpieces.

This meter comes with a 100 percent money-back guarantee and a 1-year limited manufacturer’s warranty. The manufacturer recommends automatic replacement every 3 years.

eMini-Wright Digital Peak Flow Meter USB Download Version

  • Price: $$

This digital peak flow meter is small and easy to clean. It uses a replaceable lithium battery that has a 2-year lifespan.

The device stores up to 240 readings at a time. You can download your readings directly from the meter to a PC.

To use this meter you will need a USB A to mini B cable, sold separately.

Quest AsthmaMD Lung Performance Peak Flow Meter

  • Price: $$

This mechanical, hand-held meter has a built-in handle. It’s very lightweight and portable.

The device measures a range from 60 to 810 L/m. It has two adjustable zone indicators and indicator markings at 50 L/m and 10 L/m.

Reviewers find it accurate, easy to use, and easy to clean. Some reviewers mention that the mouthpiece is oddly shaped and hard to create a seal around.

Since there are different types and brands of peak flow meters, make sure you read and follow the directions that come with your device. Generally, here’s what you can expect when using one of these devices.

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Take three readings

In general, these are the steps you can expect to take when using a peak flow meter:

  1. If possible, stand up straight.
  2. Make sure the peak flow meter’s indicator is set to the bottom of the scale.
  3. Hold the peak flow meter by its handle. Breathe in as deeply as you can.
  4. Make a tight seal around the mouthpiece with your lips.
  5. Hold your tongue down inside your mouth and quickly blow out one long breath as forcefully as you can.
  6. The peak flow meter’s indicator will move up the device to a number. This is your reading number.
  7. After your first reading has been recorded, repeat the entire process two more times. Make sure to slide the indicator down to the bottom before taking each additional reading.

Keep a record of all readings

Chart your highest reading of the three, along with the date, time, and any other significant information. Some peak flow meters come with a graph or chart you can use to record your reading numbers.

You may also wish to write down your readings manually in a notebook.

Based on your readings, follow your doctor’s instructions on exercise and medication use.

  • When your asthma is well-controlled. If your asthma is under control, you may decide to only use your peak flow meter when your symptoms increase or when you experience triggers, such as breathing in cold, dry air.
  • When you’re getting your asthma symptoms under control. If your asthma is not well-controlled, you might take peak flow readings at least once daily, at the same time each day. You may also benefit from taking readings several times per day, such as first thing in the morning and right before bed.
  • When symptoms happen. If your symptoms wake you up from sleeping or occur at specific times of the day, use your peak flow meter when symptoms occur.
  • If you have an acute respiratory illness. If you have a cold, flu, or other respiratory condition, you might use your peak flow meter more often.
  • With your medications. Your doctor may suggest using your meter right before and after you use medications, such as a rescue inhaler (inhaled albuterol).

Peak flow meters don’t require a prescription and are mostly affordable. They’re widely available online and in stores, from retailers or directly from the manufacturer.

You can also purchase a peak flow meter at a local drugstore, such as Walgreens or CVS. Your local pharmacy or medical supply store may also have peak flow meters.

When you first get a peak flow meter, your doctor may recommend you use it several times daily over a period of 2 to 3 weeks. This will provide information about your baseline readings and personal best peak flow number.

Your personal best is the highest monitor reading you record during this timeframe. This number is important, because it indicates how well you’re able to breathe when your airways are clear and have no asthmatic symptoms.

To get your personal best peak flow number, your doctor will have you use the meter at least twice a day. This may be first thing in the morning, before you use asthma medication, and once again in the afternoon or evening.

Knowing your personal best peak flow number is essential for controlling asthma. Changes in this number can alert you that your condition is worsening or that a change in your treatment plan is needed.

Once you’ve determined your personal best peak flow number, you and your doctor can establish a game plan for using the meter and data it provides. This will include establishing your personal peak flow zones.

Peak flow zones have a specific numerical range. These ranges are determined by your personal peak flow rate. When you take readings on your meter, compare them with the zone numbers, so you know which zone you’re in.

You and your doctor will have a plan for each zone. If you have a reading in the red zone, call your doctor and seek medical help immediately. Yellow zone readings may also require medical care.

When to see a doctor

You should always seek immediate medical support for signs or symptoms of a serious asthma attack.

These include:

  • severe shortness of breath
  • inability to speak more than short sentences
  • wheezing
  • straining your chest muscles in order to breathe
  • no change in breathing quality after using a rescue inhaler