Model identifies causes of nasal drying during pressurised breathing.

Patients nasally breathing pressurised air frequently experience symptoms suggestive of upper airway drying. While supplementary humidification is often used for symptom relief, the cause(s) of nasal drying symptoms remains speculative. Recent investigations have found augmented air pressure affects airway surface liquid (ASL) supply and inter-nasal airflow apportionment. However the influence these two factors have on ASL hydration is unknown. The purpose of this study is to determine how ASL supply and airflow apportionment affect ASL hydration status for both ambient and pressurised air breathing conditions. This is done by modifying and adapting a nasal air-conditioning and ASL supply model. Model predictions of change in inter-nasal airflow apportionment closely follow in-vivo results and demonstrate for the first time abnormal ASL dehydration occurring during augmented pressure breathing. This work quantitatively establishes why patients nasal breathing pressurised air frequently report adverse airway drying symptoms. The findings from this investigation demonstrate that both nasal airways simultaneously experience severe ASL dehydration during pressurised breathing.