Oropharyngeal deposition of 3.5 microns particles inhaled through an elongated mouthpiece

Abstract

We previously studied the deposition of inhaled particles in the oropharynx of asthmatic patients, and found that a pharyngeal narrowing during inhalation seems to be one reason for high oropharyngeal deposition. In the present study, we investigated whether by-passing a larger part of the oral cavity by using an elongated mouthpiece would reduce deposition in the oropharynx, and increase deposition in the lungs. Deposition in the oropharynx and in the lungs was estimated in nine patients with obstructive airway diseases. In earlier investigations, three of these patients had repeatedly shown extremely high oropharyngeal deposition (> 70%). In the present study, the patients inhaled 3.5 microns (aerodynamic diameter) radiolabelled Teflon particles at 0.5 L.s-1, with and without an individually adapted elongated mouthpiece. Radioactivity was measured using a profile scanner. On average, oropharyngeal deposition was 27% (range 12-45%) and 30% (range 11-77%) of the total amount of particles deposited in the body, with and without elongated mouthpiece, respectively. There was no significant difference between these values (p > 0.05), nor between the values of lung deposition. However, oropharyngeal deposition was markedly reduced, with a corresponding increase in lung deposition, by the elongated mouthpiece in the one and only patient who still showed extremely high oropharyngeal deposition (> 70%). Our study shows that lengthening of the mouthpiece is not sufficient to reduce average deposition of aerosol particles in the oropharynx in patients with comparatively normal deposition values. This result, however, does not exclude a beneficial effect in patients with extremely high oropharyngeal deposition.