Peak Flow Meters

How To Monitor Your Asthma

To better monitor and manage your asthma and understand how your asthma may change during the day or over a longer period of time, your health care provider may ask you to use a Peak Flow Meter.

A Peak Flow Meter estimates the Peak Expiratory Flow Rate, which is a measure of the fastest speed at which you can exhale the air from your lungs, after inhaling a big breath. The measurement relates to how well the air is moving through your airways, so if asthma is present with airway inflammation or bronchoconstriction, the peak flow levels will be lower. Three peak flows are measured in succession and the best reading is recorded. This measurement can also be done before and after inhalation of your reliever medication.

The measurement is recorded daily or twice daily and written in a diary to help recognize changes in your peak flow that may occur during the day or over time. A decrease over time may show that your asthma is worsening and vice versa, an increase in measured values will indicate increased asthma control or response to inhaled controller medications.

Normal values for peak flow measurements are dependent on age, sex and height. Each person will have his or her own best peak flow measures. Based on the best peak flow, a decrease in peak flow may indicate a loss of asthma control so the patient can refer to their Asthma Action Plan for appropriate action. Your Health Care Provider will review your measurements at follow up visits and assess your need for ongoing medications and updates to your Asthma Action Plan.

There are two types of Peak Flow Meters:

• A Mechanical Peak Flow Meter will allow you to measure PEF (Peak Expiratory Flow), the speed of the air blown out of your lungs.
• A Digital Asthma Monitor will allow you to measure PEF (Peak Expiratory Flow) and FEV1 (Forced Expiratory Volume in 1 second), the volume of air expelled within the first second.

Digital Peak Flow Meter

Digital Asthma Monitors, also known as Digital Peak Flow Meters, measure:

• Peak Expiratory Flow (PEF) – the maximum speed at which you can exhale air from your lungs, after inhaling a big breath.
• Forced Expiratory Volume in 1 second (FEV1) – the volume of air expelled within the first second, after inhaling a big breath.

Both measurements relate to how well the air is moving through your airways, which in turn, really means how open the airways are. If asthma is present with airway inflammation or bronchoconstriction, the peak flow and/or FEV1 levels will be lower as there is airway narrowing. These tests may be similar to ones you perform at your physicians’ office.

The measurements are made and recorded once or twice daily and can be easily downloaded using special computer software. These results can be shared with your health care provider by sending the obtained measurements by e-mail or by bringing the results to your next appointment.

Using the Asthma Monitor for these measurements allows you to monitor your asthma on a day to day basis and will help determine the effectiveness of prescribed anti-inflammatory (controller) medications.

If monitoring shows a decrease in these values over time, this may show that your asthma is worsening, meaning a loss of asthma control. On the other hand, an increase in measured values will indicate increased asthma control or response to controller medications.

It is important that you perform these measures with your healthcare provider before your self monitoring begins to ensure you are doing the measures correctly. For more information about the Asthma Monitor, talk to your doctor, pharmacist, or a Certified Respiratory Educator.

Peak Flow Monitoring at Home

To monitor how well your asthma is controlled, your doctor may suggest you use a peak flow meter.

This simple device measures what’s called your “peak expiratory flow,” or PEF. Using it, you can:

• Determine whether your peak flows vary over time, or are affected by the presence of certain triggers
• Monitor how well your medication is working
• Recognize whether you require immediate medical attention
• Develop an Asthma Action Plan, a tool that helps you keep your asthma under control

Using a Peak Flow Meter

Using a peak flow meter is simple. Read the instructions that come with your particular model, and follow these steps:

1. Attach the mouthpiece to the peak flow monitor.
2. Set the marker (indicator) to the level of zero on the scale.
3. Stand up or, if you can’t stand, sit up straight.
4. Breathe in as deeply as you can.
5. Close your lips around the mouthpiece.
6. Blow out as hard and as fast as you can. (i.e., A “fast blast” of air)
7. Note the number next to the marker.
8. Repeat steps 2 through 7 two more times.
9. In a notebook or diary, record the highest of the three numbers. This number is your PEF for that morning or evening.

Making Sense of Your Results

Your doctor or asthma educator will help you determine which of your PEF measurements should be used as a “baseline” – that is, your personal best peak flow. Use your peak flow result with your written Asthma Action Plan to determine the action needed to be taken to manage your asthma.

Once you know your personal best peak flow, you will be able to know if your asthma is well-controlled. If the result of a PEF test is 80 per cent or more of your personal best number, your asthma is likely well controlled.

If it is less than 80 per cent of your personal best you are not well controlled. Discuss your results with your doctor.

Remember that a peak flow meter can be a useful tool, but monitoring your symptoms is the most important way to assess overall how well your asthma is being managed.