Human deposition and clearance of 6-micron particles inhaled with an extremely low flow rate.
In human experimental data, tracheobronchial deposition reaches its maximum for particles of about 6 microns inhaled at 0.5 L/s. The purpose of the present study was to investigate if tracheobronchial deposition of 6-microns particles could be increased, especially in the smaller bronchi, using an extremely slow inhalation rate. Six healthy nonsmokers inhaled monodisperse 6-microns (aerodynamic diameter) Teflon particles labeled with 111In at 0.04 L/s. Radioactivity in mouth and throat, lung, and stomach was measured immediately after inhalation by profile scanning and in the lung also after 24, 48, 72, and 96 h. There was a substantial clearance between 24 and 72 h; around 20% of the total clearance occurred between 24 and 72 h. This is in contrast to earlier studies in which only around 1% of 6-microns particles inhaled at 0.5 L/s cleared between 24 and 72 h. This indicates a markedly higher deposition in the smaller bronchi at 0.04 L/s than at 0.5 L/s. The total tracheobronchial deposition was 50%, compared to about 30% when particles were inhaled at 0.5 L/s. These findings could be therapeutic use. They also implicate the possibility of developing a diagnostic model that can separate between bronchial reactivity in large and small bronchi.
Anderson
M
M
Division of Inhalation Toxicology, Karolinska Institute, Stockholm, Sweden.
Philipson
K
K
Svartengren
M
M
Camner
P
P
D000328:Adult; D000336:Aerosols; D001980:Bronchi / Q000502:physiology*; D005260:Female; D006801:Humans; D007205:Indium Radioisotopes; D008297:Male; D008875:Middle Aged; D009079:Mucociliary Clearance / Q000502:physiology; D010316:Particle Size; D011138:Polytetrafluoroethylene; D012119:Respiration / Q000502:physiology; D012143:Respiratory Physiological Phenomena; D013997:Time Factors; D014132:Trachea / Q000502:physiology*
D000336:Aerosols; D007205:Indium Radioisotopes; D011138:Polytetrafluoroethylene