New insight into air flow distribution in alveoli based on air- and saline-filled lungs

Understanding flow distributions in human lungs has attracted significant attention since the last few decades. However, there are still large discrepancies between different studies in the distribution of air flow into alveoli at different generations of bifurcation. In this study, a new method has been developed to calculate expansion ratio of alveoli and ratio of alveolar to ductal flow rate at different generations for air- and saline-filled lungs. The effects of alveolar number, breathing period, lung tidal volume, and surface tension are examined. It is found that the expansion ratio of alveoli varies significantly at different generations in the saline-filled lungs. For the air-filled lung, the expansion ratio of individual alveolus remains constant for different generations. The current study provides new data on the flow rate ratios which is critical for understanding flow distributions and flow behaviors in alveoli. Surface tension in alveoli and alveolar number has obvious effects on the value of flow ratio. The current study sheds new light into the flow behavior in lungs and lays the foundation for detailed study on flow and particle transport characteristics in human lungs.