Asthma: Use a peak flow meter to gain control

A peak flow meter is a simple, easy-to-use device that measures how well your lungs are working. By measuring how efficiently you can breathe air out of your lungs, peak flow readings can help you identify worsening asthma so that you can adjust your treatment. Along with carefully watching your symptoms, you can use peak flow readings to help determine what steps you need to take to keep your asthma under control.

With time on your side, you can adjust your asthma medication and take other steps to help prevent an attack. In some cases, you may even notice changes in your peak flow before you have any signs or symptoms. A peak flow meter can be especially important if you have a hard time judging the severity of your symptoms, you have had severe asthma attacks, or you have moderate or severe asthma.

How a peak flow meter helps you

A peak flow meter allows you to accurately measure day-to-day variations in your breathing. When your asthma is under control, your airways are open and you can force more air into the peak flow meter. But when your airways are inflamed and constricted, you can't blow as hard into the meter — making your peak flow rate lower.

These readings will help you and your doctor:

• Determine the severity of your asthma
• Evaluate the effectiveness of your current treatment
• Determine when to add or stop certain medications
• Recognize an asthma attack before signs or symptoms appear
• Decide when to seek emergency care

Determining your personal best

Your "personal best" peak flow rate is the highest peak flow rate you can reach over a two- to three-week period when you feel good and have no asthma symptoms. This flow rate serves as a benchmark in your daily self-management plan. Because everyone's asthma is different, your personal best will be unique to you.

Your doctor will help you determine your personal best. Typically, you'll take readings once or twice a day for two weeks when you're not having symptoms. The highest consistent reading during the trial period is your personal best.

Organizing your peak flow zones

Your doctor will use your personal best peak flow rate to set your peak flow zones. Each zone is determined by your peak flow rate and symptoms. The color code for each zone reflects progressively more severe symptoms:

Green zone = stable

• Your peak flow rates are 80 percent to 100 percent of your personal best, an indication that your asthma is under control.
• You probably have no asthma signs or symptoms.
• Take your preventive medications as usual.
• If you consistently stay within the green zone, your doctor may recommend reducing your asthma medication.

Yellow zone = caution

• Your peak flow rates are 50 percent to 80 percent of your personal best, an indication that your asthma is getting worse.
• You may have signs and symptoms such as coughing, wheezing or chest tightness — but your peak flow rates may decrease before symptoms appear.
• You may need to increase or change your asthma medication.

Red zone = danger

• Your peak flow rates are less than 50 percent of your personal best, an indication of a medical emergency.
• You may have severe coughing, wheezing and shortness of breath. Stop whatever you're doing and use a bronchodilator or other medication to open your airways.
• Your asthma action plan will help you decide whether to call your doctor, take an oral corticosteroid or seek emergency care.

If your flow readings fall too far below your personal best — into the yellow or red zone — you'll need to take action to prevent or minimize an asthma attack.

How to use your peak flow meter

Peak flow meters are available over-the-counter, and they're easy to use. Here's the correct way to use a peak flow meter:

1. Move the marker to the bottom of the numbered scale, and connect the mouthpiece to the peak flow meter.
2. Stand up.
3. Take a deep breath, filling your lungs completely.
4. Place your lips tightly around the mouthpiece. Blow as hard and as fast as you can with a single breath.
5. Note the final position of the marker. This is your peak flow rate.
6. Blow into the peak flow meter two more times. Record the highest reading of the three in your asthma diary.

For the most accurate readings, it's important to keep your peak flow meter clean. Follow the manufacturer's instructions on how to take care of your peak flow meter.

When should you use your peak flow meter?

Your doctor may recommend using a peak flow meter at least once a day — typically before you take your regular asthma medication in the morning. Use the peak flow meter at the same time every day, and record your peak flow rate in an asthma diary. If your asthma is under control most of the time, your doctor may say it's OK to check your peak flow readings every few days instead of every day.

In addition to regular monitoring, you may also need to check your peak flow when:

• Asthma symptoms wake you up at night
• You have increased symptoms during the day
• You have a cold, flu or other illness that affects your breathing
• You need quick relief "rescue medication" (Check your peak flow before you take rescue medication. Then check it again after 20 or 30 minutes.)

Use an asthma action plan

An asthma action plan is a simple but important part of managing your asthma. It helps you keep track of which medications to take and what doses you need, based on which peak flow zone you're in. It clearly lists what steps you need to take for each zone. Work with your doctor to create this written plan — and make sure it's up to date. Keep your plan readily available so that you'll know exactly what to do if you have an unexpected asthma flare-up.

Peak flow: Just one tool for asthma control

Using a peak flow meter can be an effective tool for managing your asthma — but there are other things you need to do too:

• Monitor your symptoms. When it comes to keeping tabs on your asthma — and knowing which steps to take to keep it under control — watching your symptoms can be just as important as peak flow.
• Identify your triggers. Pay attention to things that trigger your asthma symptoms or make them worse — and avoid them.
• Meet with your doctor. Even if your asthma's under control, meet with your doctor on a regular basis to review your asthma action plan and revise it as needed. Asthma symptoms change over time, which means your treatment may need to change too. Show your doctor how you're using your peak flow meter, just to make sure you're doing it correctly.
• Stay healthy. Healthy choices such as eating right, getting regular exercise and not smoking can make a big difference in managing your asthma.