Tracheomalacia

This is collapse of the main windpipe (trachea) rather than the voicebox and is much less common than laryngomalacia.  The noisy breathing is often on breathing out (expiration) and can cause blue spells when the collapse is severe.  The collapse tends to get worse for a while before improving by about 2 years of age.

read a paper on  laryngotracheomalacia and tracheomalacia