| Institution: | (1) Health Effects Laboratory Division, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, 26505, WV;(2) School of Aeronautics and Astronautics, Purdue University, West Lafayette, 47907, IN;(3) Department of Physiology, West Virginia University, Morgantown, 26505, WV;(4) Department of Electrical Engineering, West Virginia University, Morgantown, 26505, WV;(5) NIOSH, 1095 Willowdale Road MS 2015, Morgantown, 26505, WV |
| Abstract: | Airway closure and gas trapping can occur during lung deflation and inflation when fluid menisci form across the lumina of respiratory passageways. Previous analyses of the behavior of liquid in airways have assumed that the airway is completely wetted or that the contact angle of the liquid-gas interface with the airway wall is 0 , and thus that the airway fluid forms an axisymmetric surface. However, some investigators have suggested that liquid in the airways is discontinuous and that contact angles can be as high as 67. In this study we consider the characteristics of constant curvature surfaces that could form a stable liquid-gas interface in a cylindrical airway. Our analysis suggests that, for small liquid volumes, asymmetric droplets are more likely to form than axisymmetric toroids. In addition, if the fluid contact angle is greater than 13, asymmetric droplets can sustain larger liquid volumes than axisymmetric toroids before collapsing to form menisci. These results suggest that (1) fluid formations other than axisymmetric toroids could occur in the airways; and (2) the analysis of the behavior of fluids and the development of liquid menisci within the lungs should include the potential role of asymmetric droplets. |
