[Investigations of nasal deposition efficiency of wheaten flour and corn starch].

BACKGROUND

In-vivo-evaluation of the nasal deposition efficiency is problematic, because a postnasal measurement of the dust particle concentration is difficult. A new method is represented, which measures in front of the nose the dust loading after ortho- and retronasal passage relative easily.

METHODS

36 healthy subjects were nasally dust-exposed sitting in an exposure chamber. With the help of dust sampling system (Respicon) the particle size-referred dust loading before and after the nasal airflow passage was gravimetrically determined. The constant flow rate was 3.111 per minute. A contamination with breathing air was excluded by an active velopharyngeal closure. The subjects breathed orally over a breathing tube clean air. They were in each case 15 min exposed to the constant pre-nasal wheaten flour or corn starch dust produced over a brush disperser (Palas, RBG 1000). The time interval between both exposures was seven days excluding cross over effects.

RESULTS

The deposition efficiency of both types of food powder was particle size dependent. Highest it was -as expected- with the particle sizes between 5-100 microm. Here it lay between 92% and 99%. The small particles of wheaten flour respective corn starch with an aerodynamic diameter between 1-4 microm deposited nasally 31% respectively 74%.

CONCLUSIONS

The new relatively simple method of measurement of nasal deposition efficiency does not load the deeper respiratory tract. The results confirm the good filtering capability of the healthy nose for large dust particles. The nasal deposition of particles smaller than 5 microm is reduced but not absent. The small dust particles of wheaten flour and corn starch are very different nasally deposited. The different electrostatic charges of the two food powders may explain these differences.