Mouth breathing, dry air, and low water permeation promote inflammation, and activate neural pathways, by osmotic stresses acting on airway lining mucus

Abstract

Respiratory disease and breathing abnormalities worsen with dehydration of the upper airways. We find that humidification of inhaled air occurs by evaporation of water over mucus lining the upper airways in such a way as to deliver an osmotic force on mucus, displacing it toward the epithelium. This displacement thins the periciliary layer of water beneath mucus while thickening topical water that is partially condensed from humid air on exhalation. With the rapid mouth breathing of dry air, this condensation layer, not previously reported while common to transpiring hydrogels in nature, can deliver an osmotic compressive force of up to around 100 cm H 2 O on underlying cilia, promoting ATP secretion and activating neural pathways. We derive expressions for the evolution of the thickness of the condensation layer, and its impact on cough frequency, inflammatory marker secretion, cilia beat frequency, and respiratory droplet generation. We compare our predictions with human clinical data from multiple published sources, and highlight the damaging impact of mouth breathing, dry air, and high minute volume on upper airway function. We predict the hypertonic (or hypotonic) saline mass required to reduce (or amplify) dysfunction by restoration (or deterioration) of the structure of ciliated and condensation water layers in the upper airways, and compare these predictions with published human clinical data. Preserving water balance in the upper airways appears critical in light of contemporary respiratory health challenges posed by the breathing of dirty and dry air.

Nil per os in the management of oropharyngeal dysphagia—exploring the unintended consequences

“…The respiratory system is vulnerable to the adverse effects of dehydration associated with NPO. Humidification is necessary for optimizing the integrity and function of the mucosa lining the upper and lower airway ( 50 , 51 ). When the mucosa becomes dry, this increases the potential risk for injury, inflammation and infection ( 52 , 53 ).…”

“…Changes in the environment and physiology can affect mucus production as well as the composition and viscosity of mucus ( 50 , 51 , 54 ). When mucus becomes thicker, this can interfere with the normal mechanisms for clearing mucus from the respiratory tract thus leading to the accumulation of mucus ( 50 , 51 , 55 ). When respiratory muscles lose hydration, mucociliary clearance and cough function can become impaired ( 33 , 55 , 56 ).…”

“…Ciliary function can also be affected when hydration is reduced. Dehydration can cause cilia to move more slowly which affects their capacity to clear mucus and foreign particles from the airway, a phenomenon documented in specific conditions such as cystic fibrosis ( 50 , 51 , 55 ). The accumulation of mucus and impaired ciliary function creates an environment that is more conducive to the colonization of bacteria and viruses thus increasing the risk of respiratory infections ( 50 , 51 , 55 ).…”

“…Changes to hydration and humidification may adversely affect voice production impacting an individual's ability to communicate effectively ( 59 , 60 ). Hydration in the upper airway is important for optimizing sensory functions of the laryngeal mucosa ( 50 , 62 – 64 ).…”