<prompt> Reversible airway obstruction is defined as ___ percentage increase in FEV1, 15 minutes after an inhaled sho-acting beta 2 -agonist therapy-_ 5_10_ 15_ 20  <response>: Diagnosis of reversible airway obstruction or asthma is made when FEV1 15 and 200 ml increase following administration of a bronchodilator ,like sho acting beta2 agonists, or trial of coicosteroids.It can also be diagnosed as 20 diurnal variation on 3 days in a week for 2 weeks on PEF diary FEV1 15 decrease after 6 mins of exercise. Reference:Davidsons medicine-22nd edition,page no:668 