Abstract

Purpose: High concentrations of inhalable particulate matter (PM, aerodynamic diameter 2.5–10 µm) are associated with increased risks of respiratory diseases, cardiovascular diseases, and adverse pregnancy outcomes. PM can disrupt the nasal epithelial barrier, leading to vulnerability to respiratory disease. Nasal saline washing can help support nasal functioning by removing trapped PM. We aimed to determine which nasal saline administration technique provided the best intranasal saline deposition and to assess the effectiveness of intranasal saline cleansing solutions for removing PM-simulating dust. Methods: We conducted 3 in vitro studies using a nasal cast coated with an artificial mucus. Study 1 evaluated the deposition patterns of 3 nasal sprays administered with different techniques. A lateral image was taken after each administration to quantify the exposure area. Studies 2 and 3, in which PM-simulating dust was added to the nasal cast, evaluated the effectiveness of 4 intranasal saline sprays administered with the line-of-sight (LoS) method (head tilted sideways 45°, spray angle 0° from vertical) for washing away PMsimulating dust. The percentage of PM removed was quantified from pre- and post-washing images and from a high-accuracy liquid particle counter analysis of cast run-out. Results: Study 1 demonstrated that the LoS method provided the best intranasal saline deposition. Studies 2 and 3 showed that intranasal saline administration with this method effectively recovered and removed the PM-simulating dust from the mucus-coated cast. Conclusion: These results support the benefit of nasal saline washing with LoS administration, suggesting that this method should be recommended for nasal spray use to effectively remove PM. Future investigations are warranted to explore the benefits of nasal washing in a variety of clinical settings. Nasal saline cleansing can help preserve and maintain normal nasal functioning, possibly with long-term effects of helping to reduce the impact of air pollution on health.

Keywords

air pollution, nasal mucosa, nasal sprays, saline solution, particulate matter, respiratory system