DoDMERB
If you are new to this forum you will quickly learn about the expertise of Larry Mullen, Deputy Director at DoDMERB. He is awesome and will walk you through this. You can email him at Larry.Mullen@dodmerb.tma.osd.mil with your son's name, last four of his social security number and a description of what your question is. You can read through other threads and see how he has helped so many people!
As far as a general response to your question: I'm assuming your son has/had asthma. The test that you are referring to is a type of pulmonary function testing done where lung volumes are checked before and after being given an a bronchodilator (a type of inhaler medication used for asthma.)