Airway geometry, airway flow, and particle measurement methods: implications on pulmonary drug delivery

ABSTRACT

Introduction: The effectiveness of drug delivery to the lungs is inextricably linked to the fundamental interactions that occur between particles and flow in the extrathoracic airway. Research in this field requires time resolved in-vivo and in-vitro measurements of three separate, yet intricately linked parameters: i) airway flow, ii) airway geometry, and iii) drug particle characteristics. A number of recent significant developments have been made in the experimental diagnostic tools used to characterise these parameters.

Areas covered: In this review paper, we summarize the key recent findings that have resulted from the implementation of laser and optical diagnostic tools towards characterization of airway flow, extrathoracic airway geometry and drug particle characteristics. These three areas are discussed together, enabling a critical review of the implications of recent experimental findings on likely future developments in drug delivery to the lungs.

Expert opinion: Improvements in drug delivery systems will result through implementation of laser and optical based diagnostic methods that can spatially and temporally resolve particle and agglomerate shape, size and dynamic characteristics. Design of inhaler devices must be done in parallel to developing realistic in-vitro upper airway replicas that account for physiological differences between patient groups, as a function of respiratory disease severity.

KEYWORDS:

• Pulmonary drug delivery
• dry powder inhalers
• upper airway
• laser diagnostics

Article Highlights

• Recent measurements of airway flow from simplified and physiologically representative in-vitro models are discussed in the context of pulmonary drug delivery

• Laser and optical diagnostic methods applicable to the characterization of drug particle dynamics are reviewed and compared with a focus on recent developments

• Techniques used towards the characterization of upper airway physiology and motion are presented with key findings discussed in the context of drug delivery

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Additional information

Funding

This paper is not funded