Trick of the Trade: Blow out a candle
With your stethoscope positioned on the patient's back, ask the child to pretend like they are blowing out a birthday candle. Personally I have had variable success with this trick, because the child has to imagine a candle in front of them. Sometimes it works, but other times they just look at me like I'm crazy.
However, what if they had a virtual candle in front of them?
Trick of the Trade (high tech): Candleflame iPhone app
This free iPhone app displays a virtual candle burning for about 20 seconds. It is a slight hassle because a brief ad pops up at the beginning, which you have to manually select to skip over. It's worth the minor hassle, because one can blow out the candle if you sufficiently blow hard enough at the virtual candle. The sensor is the iPhone speaker piece at the bottom of the unit.
Since then, I have used this as a means to grossly assess an asthmatic child's peak flow ability if s/he can't coordinate using a peak-flow meter. You can adjust and increase the distance from the child to the iPhone to encourage maximal expiratory effort.
(Turn audio on in this video to hear me blowing out the candle.)
