Asthma: Measuring Peak Flow

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Asthma: Measuring Peak Flow

Introduction

As someone with asthma, you know how important it is to monitor your condition. You need to know how well your lungs are "working": is their ability to move air in and out staying the same, or is it getting better or worse?

When you monitor your asthma, you can control it. When you control your asthma, you also control your life—you do what you want to do, and your asthma does not limit you.

Measuring your peak expiratory flow is an important part of monitoring your asthma.

 

Peak expiratory flow (PEF) measures how fast you breathe out when you try your hardest. It tells you how well your lungs are working. You measure PEF with a peak flow meter, an inexpensive device that you can use at home.

  • If you can breathe out quickly and with ease, you will have a higher number (higher peak flow rate). Your lungs are working well, and your asthma may not be bothering you.
  • If you can only breathe out slowly and with difficulty, you will have a lower number (lower peak flow). This may mean that your lungs are not working well, even if you don't have any of your usual asthma symptoms.

You measure PEF as litres of air per minute.

How often should I measure PEF?

How often you measure your PEF depends on how severe your asthma is and how often you have asthma attacks. If you have severe asthma or cannot tell when you are having asthma symptoms, you may need to check your PEF twice a day, in the morning and in the evening. If you have mild asthma, you may not need to check your PEF daily and can instead monitor it by paying attention to symptoms. However, if any asthma symptoms develop, you may need to check your PEF. Talk with your doctor about how often you check your PEF.

Test Your Knowledge

What does PEF measure?

Continue to Why?

 

Measuring your PEF is important, because it lets you:

  • Determine your asthma zones, which you use in your asthma action plan. During an acute asthma attack, which zone you are in determines your medicine and action.
  • Know whether an acute asthma attack is going to occur and how severe it may be. If you know you are going to have an asthma attack, you can take medicine to prevent it or make it less severe. This may help you avoid having to go to the emergency room.
  • Identify things that may trigger an asthma attack, such as pollen, cigarette smoke, or dust mites.
  • Measure changes in your breathing. This can help your doctor to:
    • Decide whether you need to change, increase, or decrease the long-term medicine used in your daily asthma treatment plan.
    • Tell which medicines are helping your breathing and which are not.

Test Your Knowledge

Measuring your PEF can help you know if you may have an asthma attack.

  • True
    This answer is correct.

    Measuring your PEF can help you know if you may have an asthma attack. It also helps you determine your asthma zones, identify triggers, and measure changes in your breathing.

  • False
    This answer is incorrect.

    Measuring your PEF can help you know if you may have an asthma attack. It also helps you determine your asthma zones, identify triggers, and measure changes in your breathing.

  •  

Continue to How?

 

If you have never used a peak flow meter, talk with your doctor about how to use it correctly, and then practice using it.

Measure your PEF routinely. Check your breathing regularly, even if you are feeling good. PEF is lowest in the early morning and highest in the afternoon. When you measure your PEF once a day, it needs to be done first thing in the morning before you use your asthma medicine.

It's very important to record the results of your PEF measurements in your asthma diary. This will help you measure changes in your breathing. Take your asthma diary with you when you see your doctor so you can review it together. It's very important to review the diary with your doctor whenever you feel your lung function is getting worse.

How to measure your peak expiratory flow

Remove any gum or food you may have in your mouth. View a slideshow of how to measure your peak expiratory flow. Repeat the steps two more times. After you have blown into the meter three times, take the highest number you received, and write it in your asthma diary or on another record sheet.

If you cough or make a mistake during the testing, do the test over.

Different brands of meters may give different values for results. If you change meters, you will need to determine your asthma zones using the new meter.

Note: If your best effort is in your red zone, take your relief medicine immediately and call your doctor or go to the emergency room.

Test Your Knowledge

When you measure your PEF once a day, it needs to be done first thing in the morning before you use your asthma medicine.

  • True
    This answer is correct.

    When you measure your PEF once a day, it needs to be done first thing in the morning before you use your asthma medicine.

  • False
    This answer is incorrect.

    When you measure your PEF once a day, it needs to be done first thing in the morning before you use your asthma medicine.

  •  

Continue to Where?

 

Talk with your doctor

  • If you have questions on this information, take it with you when you visit your doctor. Make notes about what you would like to ask about or discuss.

If you would like more information on asthma, the following resource is available:

Organizations

Allergy/Asthma Information Association (AAIA)
295 The West Mall, Suite 118
Toronto, ON M9C 4Z4
Phone: 1-800-611-7011
(416) 621-4571
Fax: (416) 621-5034
Email: admin@aaia.ca
Web Address: www.aaia.ca
 

The Allergy/Asthma Information Association (AAIA) provides information and education materials for Canadians with allergy and asthma.


Asthma Society of Canada
130 Bridgeland Avenue
Suite 425
Toronto, ON  M6A 1Z4
Phone: 1-866-787-4050 toll-free
(416) 787-4050
Fax: (416) 787-5807
Email: info@asthma.ca
Web Address: www.asthma.ca
 

The Asthma Society of Canada provides information and education programs for Canadians with asthma and supports asthma research.


Canadian Lung Association
3 Raymond Street
Suite 300
Ottawa, ON  K1R 1A3
Phone: 1-888-566-5864
(613) 569-6411
Fax: (613) 569-8860
Email: info@lung.ca
Web Address: http://www.lung.ca/
 

The Canadian Lung Association focuses on research, education, and the promotion of respiratory health. The organization offers educational information on a variety of diseases and environmental threats, as well as information on research, support groups, and resources for children and teachers. Call to find a local office in your area.


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Credits

By Healthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Primary Medical Reviewer Brian D. O'Brien, MD - Internal Medicine
Specialist Medical Reviewer Lora J. Stewart, MD, MPH - Allergy and Immunology, Pediatrics
Last Revised May 11, 2011

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.