Filtration of droplets in the nose of the rabbit

Abstract

A mixture of 0.083 ml. atomized Apiezon oil B per cu. meter of air was passed through the nasal passages of anesthetized rabbits at pressures from 0.35 to 4.2 cm. of water and rates from 1 to 2 liters per min. Samples from the original mixture and from a tracheal cannula were sedimented on cover slips and counted microscopically. The volume of the original droplets was estimated from their diam. and focal length on the assumption that they were small plano-convex lenses with spherical surface. Percentage passage through nasal passages: 0.4- to 2-u droplets, 51 to 100% (av. 80%); 2- to 4-[mu] droplets, 37 to 88% (av. 60%); 4- to 11-[mu] droplets, 6 to 33% (av. 17%). Deposition of larger droplets is explained as due to the inertia of the droplets sufficing to carry them across the streamlines of flow into the bounding walls in the maxillo-turbinal region where channels are 0.1 to 0.5 mm. wide. On theoretical grounds, particles above 7 [mu] will be filtered by the nose, particles from 1.5 to 0.005 [mu] will pass through the nose, and particles below 0.005 [mu], corresponding to mol. wt. below 10,000, will show sufficient gaseous diffusion to reach the walls and be absorbed.