Airway surface liquid depth imaged by surface laser reflectance microscopy

Area of Science:

• Pulmonary Medicine
• Biophysics
• Medical Imaging

Background:

• The airway surface liquid (ASL) is crucial for normal airway function and implicated in cystic fibrosis pathophysiology.
• Current ASL depth measurement relies on scanning confocal microscopy, requiring fluorescent dye staining.

Purpose of the Study:

• To introduce a simple, noninvasive imaging method for measuring ASL depth using laser reflectance.
• To validate the method and demonstrate its application in measuring transepithelial fluid transport.

Main Methods:

• Utilized a 670-nm micro-focus laser to illuminate epithelial mucosa at a 45-degree angle with a rectangular beam.
• Employed reflectance imaging to capture specular and diffuse reflections from air-liquid, liquid-liquid, and liquid-cell interfaces.
• Validated the technique with known fluid thicknesses and applied it to cell cultures and ex vivo pig trachea.

Main Results:

• The reflectance imaging method successfully measured ASL depth with micron resolution.
• The technique was adapted to dynamically measure transepithelial fluid transport.
• Demonstrated comparable results to confocal microscopy without the need for dye or expensive equipment.

Conclusions:

• Surface laser reflectance microscopy provides a simple, noninvasive, and potentially cost-effective method for ASL depth measurement.
• This technique eliminates the need for dye staining and may be adaptable for in vivo applications via fiberoptics.
• Offers a valuable tool for research in normal airway physiology and cystic fibrosis.