To the Editor: The article entitled "Mist Therapy in Lower Respiratory Tract Infection" by R. C. Kelsch, et al (Amer J Dis Child109:495 [June] 1965) reports a study designed to evaluate the effectiveness of mist tent therapy in the treatment of lower respiratory tract disorders. The mist nebulizer used is a type of "croupette" unit made by the Air Shields Company that produces a majority of particles below 4μ in diameter. These particles should be effectively deposited in the smaller airways. This study finds no benefit from such therapy in a controlled series.
The authors used only water in the croupette nebulizer. Mist tent therapy involves the deposition of particles of water (beyond normal humidification) on the surfaces of the tracheobronchial tree. If a stabilizing material such as propylene glycol or glycerol is not used, the water droplets will evaporate as the air is warmed and humidified as