My son had a peak flow meter test and his results show 79. Normal is supposed to be above 90. He used to get asthma attacks but he hasn't shown any symptoms in over a year. No wheezing or shortness of breath. Is there any damage being done to his lungs if his peak flow results are showing 79 and he's not taking any medicines? Doesn't damage occur only when he is having symptoms or asthma attacks?