Exploring deposition features within an anatomy-guided uniaxial human respiratory system: a synergy of experiments and simulations

New methods that are more efficient and non-invasive are on the rise in drug delivery. One common example is intra-nasal sprays that focus on absorption rather than traditional injection. Specific regions within the airway, such as the nasopharynx for treating respiratory infections and the olfactory roof for direct access to the central nervous system via the blood-brain barrier, are of significant interest for targeted drugs. To explore the essential features of flow-geometry coupling in respiratory drug delivery, we have digitally developed a uniaxial tract that captures the basic geometric features of a 3D medical scan-based airspace topology, spanning the region from nostrils to the tracheal base. The 3D-printed cast of the uniaxial tract is designed from resin to replicate respiratory lining better. In physical experiments, with inhalation replicated by a pressure pump at the cast's outlet, generic nasal sprays with color markers are administered into the domain, and through image analysis, we have quantified the deposition pattern in terms of relative deposition efficiencies. The experimental data is segmented into cross-stream compartments and compared with full-scale computational simulations, enabling identification of the airway regions with higher drug accumulation.