A peak flow meter is a small, portable device used to measure the peak expiratory flow rate (PEFR)—how fast air is blown out of the lungs. This tool is an important part of monitoring lung function, especially for individuals managing conditions like asthma. By regularly tracking this airflow, the meter can help detect subtle changes in the airways, often signaling a worsening of asthma before symptoms become noticeable. Using this device consistently helps guide treatment decisions and can prevent severe asthma episodes.
Step-by-Step Guide to Taking a Reading
Taking an accurate peak flow reading involves a specific, forceful breath maneuver. First, ensure the sliding marker on the meter is pushed down to the zero or lowest number on the scale. Choose a consistent posture, such as standing up straight, and hold the meter by the handles.
Next, take the deepest breath possible, filling the lungs completely. Place the mouthpiece between the teeth and seal the lips tightly around it, ensuring the tongue does not block the opening. Blow out into the meter as hard and as fast as possible in a single, quick burst.
Record the number where the marker stopped, and then return the marker to zero. Repeat this entire process two more times to ensure accuracy. The highest number obtained from the three attempts is the recorded daily peak flow number, which should be logged in a chart or diary.
Determining Your Personal Best Peak Flow
The “Personal Best” (PB) reading is the highest peak flow number achieved when asthma is well-controlled and the individual feels healthy. This number is essential because it serves as the reference point against which all future daily readings will be compared. Establishing this baseline requires a temporary monitoring period of two to three weeks.
During this initial period, readings should be taken twice daily—morning and early evening—before taking any quick-relief medications. Consistency in timing and technique is necessary for an accurate result. The highest number recorded during these two to three weeks is designated as the Personal Best, which is used to set up a personalized asthma action plan.
Interpreting Your Peak Flow Zones
Daily peak flow readings are compared to the Personal Best value using a three-zone system, often color-coded like a traffic light. This system provides an immediate interpretation of lung function and dictates the necessary action. The Green Zone represents 80 to 100 percent of the Personal Best reading, indicating that asthma is well-controlled and the current maintenance treatment plan should be continued.
The Yellow Zone covers readings between 50 and 80 percent of the Personal Best and signals caution. A reading in this zone means the airways are beginning to narrow, requiring a specific intervention, such as increasing quick-relief medicine or other prescribed adjustments. If the reading falls below 50 percent of the Personal Best, it is the Red Zone, a medical alert signaling severe airway narrowing. An emergency action, including taking quick-relief medicine and seeking immediate medical care, is necessary.
Timing and Care of Your Meter
Peak flow readings are typically taken at least once daily, usually in the morning upon waking, and sometimes again between noon and 2 p.m. It is also important to take a measurement whenever asthma symptoms flare up or before and after using quick-relief medications. Recording the results helps identify patterns and track the effectiveness of treatment over time.
The peak flow meter requires regular cleaning to maintain accuracy and hygiene. The device should be washed about once a week using warm water and a mild liquid soap. After washing, rinse the meter gently and allow it to air dry completely on a lint-free towel. Because wear and tear can affect accuracy, the meter may need replacement every one to three years, or as advised by a healthcare provider.