piko and fev1

Hi to all you piko users out there.

Does anyone know how reliable the fev1 reading is. My son was in hosital this weekend and they used our peak flow meter, although his peak flow varied a bit by about 30 l/min his fev1 reading was pretty constant. If this reading is accurate I should probably speak to someone as he is only on about 30%, pf reading is just above 50%. His peak flows seem to pick up a bit better with Salbutamol than the fev1. Should these not correlate a bit better? I have noticed before that he can be quite breathless with a reasonable peak flow but has a much lower fev1.

Interested on peoples views so I can go armed with some info at outpatients appointment next week.