Lung had about 5.5 Liters at start o f the forced expiratory effort (downward arrow)

1. Express FEV1 as percent of VC (vital capacity) in part to scale up/down and account for a person being larger or smaller (large or small vital capacity) than average male/female. IF %FEV1 is greater than 80%, then they are healthy with open airways/low resistance to flow. IF %FEV1 is less than 80%, then there is reason to suggest that the airways are too narrow and there is great resistance to air flow (slow movement out of lung). Asthma and Bronchitis are common causes of low %FEV1. Bronchodilator drugs (i.e. salbuterol inhaler) may be prescribed to dilate (relax) the smooth muscle of the bronchioles and to a lesser degree bronchi. Lung had about 5.5 Liters at start of the forced expiratory effort (downward arrow) This big arrow would represent Vital Capacity (VC) VC= IRV+TV+ERV 1 second later the long had about 3 liters less volume than at the beginning (FEV1= 3L) The Math: 5.5L–3.0L= 1.5 L left over after 1 sec and slowly expired The Math For %FEV1: FEV1/VC X 100 = %FEV1 %FEV1= 3L/5.5L X 100 = 55% YES this person may have asthma This arrow show one second