peak flow readings

I use peak flow meter as well. Why you are having troubles with reading? Your best peak flow reading is when you are well. But it depends on your size age and sex, because, males have higher readings than females. The speed and force you can blow air out of your lungs depends on how open your breathing tubes are, so if you are well the breathing tubes are open and your peak flow is high, but if the tubes are tight your peak flow will fall.