The impact of expiration on particle deposition within the nasal cavity

One of the most important functions of the nose is cleansing the inspired air. The aim of this study was to compare the intranasal deposition of particles during inspiration and expiration, applying different breathing manoeuvres. In nine subjects, the non-deposited particles during inhalation of an aerosol of starch particles were laser-optically detected by placing a suction probe transnasally in the anterior nasal segment. The particle deposition was measured during cyclical nose-in/nose-out (nose-only) and nose-in/mouth-out breathing. The deposited fraction was calculated in percentages. Active anterior rhinomanometry and acoustic rhinometry were performed. The mean deposited fraction in the anterior nasal segment was statistically significantly higher (P < 0.02) during nose-only breathing (46.0%) compared with nose-in/mouth-out breathing (33.0%). Our results suggest that intranasal particle deposition takes place during inspiration as well as during expiration. The period of expiration does not only seem to be important for water and heat recovery, but also for cleansing of the respiratory air.