Research is proposed to continue the study of CO2 gas and hygroscopic aerosol particle motion within the respiratory airways. Three specific clinically important hypotheses are being tested: 1) that jet catheter design and location in high frequency jet ventilation (HFJV) in neonates have a major influence on gas exchange efficiency and tracheal wall damage and shear rate, 2) that the amount and location of airway hygroscopic aerosolized drug deposition can be controlled and maximized by relatively simple and inexpensive procedures, and 3) that important new diagnostic information on acinar airway structure can be obtained noninvasively on a living person from computer analysis of steady state CO2 washout curves recorded at the mouth. These three hypotheses are linked together by the fact that they all depend on obtaining a deeper understanding of the motion or transport of gases and aerosols along the airways by the two physical mechanisms of macroscopic convection and microscopic molecular diffusion. The methods used to test these hypotheses involve the combined use of physical and numerical computer models along with measurements on the lungs of healthy and diseased (COPD) human subjects. This combined approach has been very successful so far in elucidating many features of the airway transport process and is the optimal method of achieving progress in both theoretical understanding and practical application.
