[header] How to keep a breathing diary for asthma [title] Ask your doctor for a peak flow meter. [step] If you have moderate or severe asthma, your doctor should be able to prescribe a peak flow meter. This device takes a measurement of how fast the air moves out of your lungs. 
Your doctor should also be able to give you a peak flow chart, which allows you to record your peak flow readings. Insert or copy the chart into your asthma diary.