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Monitor asthma control with peak expiratory flow (PEF) measurements
Leave blank if unknown (will use predicted)
Good control. Continue current plan.
Caution. Use rescue inhaler, monitor closely.
Emergency! Get medical help immediately.
Stand up straight (or sit upright)
Set the marker to zero
Take a deep breath, filling lungs completely
Place mouthpiece in mouth, seal lips tightly
Blow out as HARD and FAST as possible
Record the number. Repeat 3 times, record best.
Measure twice daily for 2-3 weeks when asthma is well controlled. Your highest reading is your personal best.
Measure at the same times daily, typically morning (before medications) and evening.
Morning dip >20% from evening suggests poorly controlled asthma. Keep a log to show your doctor.
Typically twice daily (morning and evening) during periods of instability. Once daily or as needed when well-controlled. Always check when symptoms worsen.
Lung function naturally dips overnight. A "morning dip" >20% below evening values suggests airway inflammation and poor control.
FEV1 (spirometry) is more reliable for diagnosis and severity. Peak flow is useful for daily monitoring but has more variability. Both have roles.
No. Peak flow helps you monitor between visits and know when to seek help, but regular checkups, spirometry, and medication reviews are essential.
Use predicted values initially, but work to establish your personal best during a period of good control. Personal best is more meaningful than predicted.
Yes, especially when establishing baseline, after medication changes, or when poorly controlled. Share records with your doctor to guide treatment.
Every asthma patient should have a written action plan from their doctor specifying medications and actions for each zone. This calculator helps interpret readings; your plan tells you what to do.