My daughters clinic has started really focusing on the benefits of huffing recently. She is 4 and we are practicing with her daily. Here's the definition and directions they gave us:
Huffing is a maneuver performed with an open glottis; it starts from the diaphram and the chest, not the throat. Most people tend to purse their lips,, which is wrong. In order to keep the gloitis open, use a small cardboard mouthpiece and place it between the teeth. Practice blowing a cotton ball off the table. A nose piece may be required to block the nares.
Another trick to keep the gloitis open is to keep the chin up.
2 kind of huffs:
Low Huffs: Instruct child to take a normal breath and to hold it for 3-4 seconds. Very slowly and in a controlled manner, ask them to exhale as much air as they can with their mouth open. A great tool is a simple kleenex, hold it about 2 inches from your childs mouth and as they exhale the tissue should slowly rise then fall. Your child could also exhale slowly at a mirror, causing fog. At the end of the low huffs you can usually hear fine crackles coming from teh child. This is a good sign that mucus is mobilizing from the lower airways.
High Huffs:Instruct child to take deepest breath possible. Again keep gloitis open and produce a very high velocity, short exhalation "huff" This moves secretions from the lower airways to bigger airways where they can now be coughed up.