Usually we don't have to place patients having trouble breathing in this position, it's automatic.  I know because when I had bad asthma attacks as a kid I did this. I sat up, leaned on tables, whatever I could to expand my lungs.  Yet in RT school I later learned this is a natural tendency because stretching the lungs is a good way to increase surface area in the lungs for gas exhancge.  The lungs are flexable, and expanding the chest is an ideal way to get more air into the lungs.  If you worked in a hospital as I do, or if you had asthma as I do, you'd see for yourself that expanding the chest when you're having trouble breathing is a natural tendancy.  Many asthmatics lean on tables when they are in distress, stand up, or whatever to increase surface area.  This is normal for asthmatics.  Great question.