Nasal Physiology and Sinusitis

Abstract

The nose is the entry point of air and it contains the organ for olfaction and respiration. The physiological functions under respiration of the nose are humidification, filtration, and heat transfer of inspired air. The temperature regulation of inspired air is possible by the heat transfer mechanism of the nose. The number of unwanted materials in the inspired air is filtered by the nose. The unwanted materials are dust particles, pollutant, bacteria, virus, smoke, pollen, etc. Nasal vibrissae and nasal secretions are involved in the removal of these materials. The temperature of environmental air is varied in different part of the world but by humidification and heat transfer, the temperature of inspired air in posterior choana is 31 °C. Expired air helps in mucosal lubrication by condensation of water over mucosa. The inspired air runs in the parabolic form, it runs as one unit at the level of inferior turbinate then it divides into two waves at the level of the middle turbinate and reunite at the level of choana. Nasal cavity offers close to half of the total airway resistance and maximum resistance is at the level of the nasal valve. The nasal immune system protects the lower airway by neutralizing the antigens. Rhinomanometry, acoustic rhinometry, spirometry, and rhinosteriometry are used to assess the various function of the nose. Rhinosinusitis (RS) is the inflammation of sinonasal mucosa. Sneezing, nasal discharge, and obstruction are the main symptoms of sinonasal diseases. It is further classified on the basis of etiology, duration of symptoms, and severity of symptoms. Infectious and allergic are the major etiological subtypes of rhinosinusitis. Infectious type is classified clinically into the acute, recurrent acute, chronic, and acute exacerbations of chronic type. Viral infection may or may not be following by bacterial infection in acute type whereas chronic type is more organisms defined. The frontal sinus is affected most vulnerable sinus for infection because of its narrow outflow tract. The surgical procedures are divided into external and endoscopic approaches. The choice of approach is based on pathology, previous surgery, and surgeon’s expertise. Orbital and cranial cavity are the closest structures to sinonasal region so acute nasal infection can spread to these areas by natural foramina, suture line, and by route created by trauma. It is mostly managed by non-surgical way. Allergic type is accounts for 10–25% of RS. It generally involves the upper airway and it can affect the work performance significantly. It is further divided into intermittent and persistent based on the duration of symptoms. The typical history with skin prick tests and serological tests are the backbone to establish the diagnosis. The lines of management are; primary prevention by allergen avoidance, secondary prevention by medication and immunotherapy. The symptoms of intrinsic rhinitis are relatively vague, the differential diagnosis has to be excluded. The patients are generally presented with persistent nasal discharge and nasal obstruction. The absences of serum eosinophilia with negative skin prick tests are the diagnostic criteria. The medical line of management is similar with allergic rhinitis. For persistent obstruction by enlarge turbinate, the surgical procedures are focused on lateralization of turbinate and reduction of its size with mucosal preservation. Vidian nerve is the major parasympathetic supply of the nasal mucosa so vidian neurectomy is proposed to reduce the rhinorrhea symptoms. The fungus is ubiquitous in the environment and its colonization is found in the nasal cavity. Fungal sinusitis is further divided into invasive and non-invasive types. Saprophytic, fungal ball, and allergic fungal rhinosinusitis (AFRS) are the types of non-invasive form and treatment modalities are removal of disease with regular follow-up. Steroids have role in the management of AFRS. Invasive is further classified into acute and chronic types. The management is debridement of involved tissue and long-term antifungal therapy.