Aerosol delivery through nasal cannulas: an in vitro study

Area of Science:

• Medical Devices
• Respiratory Medicine
• Aerosol Science

Background:

• Nasal aerosol delivery for pulmonary medication is uncommon but potentially useful in specific clinical scenarios.
• Applications include pediatric critical care with humidified high-flow nasal cannula (HFNC) and continuous aerosol delivery for short-acting drugs.

Purpose of the Study:

• To assess the feasibility of delivering aerosols via nasal cannula in vitro.
• To quantify aerosol output and particle size distribution when using a nasal cannula system.

Main Methods:

• An Aerogen Solo nebulizer was connected to a heater/humidifier, followed by adult, pediatric, or infant nasal cannulas.
• Radioisotope techniques quantified total cannula output and system losses.
• Laser-diffraction measured aerosol size at various points, including nebulizer, heated tube, and cannula prongs.
• Testing was performed with and without an inhalation-only breathing simulator, using 3 lpm oxygen flow.

Main Results:

• Total nasal cannula output ranged from 8.4-25.1% (without inhalation) and 18.6-26.9% (with inhalation).
• Volume median diameters were approximately 2.2 µm (adult) and 1.9 µm (pediatric) from the cannula.
• 90% of aerosol volume was below 4.2 µm (adult) and 3.8 µm (pediatric).
• Highest system losses occurred in connectors, heated tube, and humidifier; nebulizer losses were minimal (2.2-3.5%).

Conclusions:

• Aerosol delivery through a humidified high-flow nasal cannula system is demonstrated to be efficient in vitro.
• Further research is needed to confirm the clinical viability of this nasal aerosol delivery route for pulmonary effects.