Filtration of particulates in the human nose

This report reviews the current theories on the deposition of inhaled particulates in the human nose. The inhalation of particulates represents a challenge to the upper respiratory tract. The concentration of airborne particulates and pollutants varies between occupational and nonoccupational exposure. Regional deposition of potentially hazardous inhaled material determines the local and systemic toxicity. In vitro experiments using casting and molding techniques with water dye models or laser Doppler anemometry indicate that nasal airflow is determined by the size of the nasal valve and the turbinates. The main airstream during inspiration passes through the lower nasal passage. Filtration capacity of the human nose can be expressed mathematically or experimentally. In vivo experiments applying monodisperse or polydisperse aerosols during single or multiple respiratory cycles have shown by using microscopic or laser-optic identification that particles larger than 3 microm have a maximum deposition in the anterior part of the nose (nasal valve). Particles smaller than 3 microm and larger than 0.5 microm are filtered by the nasal mucosa and transported by cilia propulsion to the nasopharynx. The filtration for particles smaller than 0.5 microm is low. They seem to pass easily into the lower respiratory tract. This knowledge has an impact on nasal septal surgery and rhinoplasty. By influencing the structure of the nasal valve and the lower turbinates, the filtration capacity of the nose can be significantly decreased.