Nasal pulmonary interactions

Abstract

The upper and lower respiratory airways interact in many ways. Important, well-known nasal functions include the filtering, warming, and humidification of inspired air before inhalation into the lungs. Nasal breathing also appears important in aiding oxygen absorption and in facilitating carbon dioxide excretion. Inflammation in the nasal mucosa results in lower airway inflammation and vice versa. A subsequent systemic inflammatory response amplifies the response to inflammatory stimuli in other areas of the respiratory airway. Inflammatory mediators and/or infectious pathogens may also be transported along the respiratory mucosa or through the airways. Neuronal responses may play a role, although the existence of nasobronchial reflexes remains controversial. Nitric oxide and carbon dioxide may also act as aerocrine messengers. Patients with asthma, bronchiectasis, and chronic obstructive pulmonary disease frequently have upper respiratory tract disease and vice versa. Physiological, epidemiological, and clinical evidence support a unified airway model.