Physiological aspects of ultrasonic aerosols

SummaryThe aerosol produced by an ultrasonic generator has a mass medium particle diameter of about 6 m and contains up to 200 mg of water per litre of air. In a mist tent the larger particles are lost and the mass median diameter (MMD) of the cloud is about 3 μ with a moisture content of 35 mg/l. The amount of liquid deposited in the fine airways of children during 24 h is small. Hypotonic aerosols cause coughing in man. Hypotonic and hypertonic aerosols cause damage to the lungs of animals. There is no evidence of this in man but the aerosol should probably be isotonic when inhaled and the liquid in the generator must be adjusted accordingly. Isotonic droplets do not evaporate during inhalation and the use of propylene glycol to prevent this is unnecessary.