Particle deposition and resistance in the noses of adults and children.

Nasal filter efficiency for particles has been described by several authors as showing large individual variations, probably somehow related to airflow resistance. Twelve children, aged 5.5-11.5 yrs and 8 aged 12-15 yrs were compared to a group of ten adults. Deposition of polystyrene beads (1, 2.05, 2.8 microns mass median aerodynamic diameter (MMAD] was measured by comparing inhaled aerosols and exhaled air concentrations, for both nose and mouth breathing. Ventilation was controlled to scale breathing patterns appropriate for each age either at rest or during moderate exercise to allow comparison between subjects in similar physiological conditions. Anterior nasal resistance (as a function of flow rate) and standard lung function were measured for each subject. For the same inhalation flow rate of 0.300 l.s-1, children had much higher nasal resistances than the adults, 0.425 +/- 0.208 kPa.l.1.s under 12 yrs, 0.243 +/- 0.080 kPa.l.1.s over 12 yrs and 0.145 +/- 0.047 kPa.l.1.s in adults. Individually, nasal deposition increased with particle size, ventilation flow rate and nasal resistance, from rest to exercise. The average nasal deposition percentages were lower in children than in adults, in similar conditions: at rest, 12.9 and 11.7 versus 15.6 for 1 microns; 13.3 and 15.9 versus 21.6 for 2.05 microns; 11 and 17.7 versus 20 for 2.8 microns. This was even more significant during exercise, 17.8 and 15.9 versus 29.2 for 1 microns; 21.3 and 18.4 versus 34.7 for 2.05 microns; 16 and 16.1 versus 36.8 for 2.8 microns.(ABSTRACT TRUNCATED AT 250 WORDS)