Lung function tests (also known as pulmonary function testing) is used to diagnose many lung diseases including asthma. These are non-invasive testing that has the patient blow into a tube so that lung volumes and speeds of exhaling can be measured. In asthma, the lung volumes may be normal or perhaps even elevated, but the speed of exhaling is be prolonged. Moreover, the prolonged exhaling is reversible with medicines. This is because the airways are constricted from inflammation. This inflammation can be controlled by inhaled steroids and bronchodilators such as albuterol. There are other causes of shortness of breath that can be diagnosed by pulmonary function testing, but they are quite rare in young people.
As stated above, shortness of breath in a young person can be caused by many different conditions. If your son receives a diagnosis of asthma from these tests, then you can probably follow up with his primary care physician
or family doctor). If no diagnosis is found, then he will need followup with a specialist. Shortness of breath can also be caused by other conditions such as anxiety. If this is asthma and it is severe and difficult to control, then he may need to see an allergist or pulmonologist
to for further workup and management.