Nasal nitric oxide and the nasal cycle

Area of Science:

• Otolaryngology
• Respiratory Physiology
• Medical Research

Background:

• Nitric oxide (NO) plays a crucial role in regulating vascular tone and airway function.
• Nasal patency, or the openness of the nasal airways, can vary significantly due to physiological factors like the nasal cycle and body position.
• Understanding the relationship between nasal patency and NO concentration is important for respiratory health.

Purpose of the Study:

• To investigate the correlation between varying degrees of nasal airway resistance and nitric oxide (NO) concentration within the nasal passages.
• To determine if changes in nasal patency affect NO levels delivered to the oropharynx and potentially lower airways.

Main Methods:

• Measurements of unilateral nasal NO concentration and oropharyngeal NO concentration were performed in healthy adult volunteers.
• Nasal resistance was systematically increased using a custom device, ranging from no resistance to complete nasal occlusion.
• Nasal cavity congestion was artificially induced in a subgroup to assess NO concentration under simulated physiological conditions.

Main Results:

• A significant positive correlation was observed between increased nasal resistance and elevated nasal NO concentrations, reaching up to 1109.7 ppb with complete occlusion.
• No correlation was found between oropharyngeal NO concentrations and nasal resistance.
• A strong negative correlation (r = -0.8, P <.001) indicated that smaller nasal cavity volumes were associated with higher nasal NO concentrations.

Conclusions:

• Increased nasal resistance, as experienced during the nasal cycle or in recumbency, augments NO concentration on the obstructed side of the nasal airway.
• While NO concentration within the nose varies with nasal patency, it appears to remain constant down to the lower airways.
• The precise role of the upper airways in modulating inhaled NO concentration requires further investigation.