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Understanding the nose’s physiology requires an in-depth analysis of its functions. The nose works as the only means of bringing warm humidified air into the lungs. It is the first organ for filtering out particles in the inspired air, and it also serves to produce first-line immunologic protection by drawing inspired by contact with mucus-coasted membranes that contain immunoglobulin. An (IgA). Inspired air is carried high into the nasal cavity to come in touch with the olfactory nerves, thereby giving the sense of smell, which is closely connected with the taste sensation. Dysfunction of any of this system can lead to symptoms of nasal dysfunction (e.g., postanal congestion drainage, sinus infections, facial pressure, headaches
Awareness of the link and dependencies of the upper and lower airways has increased; this concept is now known as the unified airway. The respiratory tract is thought to be an integrated system and whatever processes affect one also affect the other. Therefore, changes in the physiology of the nose and paranasal sinuses can and will affect the lower airways and visa verse.
Air flows superiorly into the nares, defined by its position and the anterior nasal valve. The airstream then shifts posteriorly roughly 90° and flows into the nasopharynx. The airstream then turns inferiorly 90° via the pharynx and larynx and passes into the trachea into the lungs. The anterior nasal valve is positioned 1.5-2 cm behind the anterior nares and is the thinnest and narrowest part of the upper airway. The small area of the upper airways enables close contact between the air stream and mucosal surfaces.
Humidification occurs due to evaporation of moisture from the mucosal blanket. Air is humidified to 75-80%.Warming of inspired air to 36°C ensues from contact between air and the body’s rich blood supply of the nasal membranes, particularly the inferior turbinate mucosa.
Adults will condition more than 14,000 liters of air per day, requiring more than 680 grams of water, nearly 20% of our daily water intake.
The Sniff is also an essential component of nasal airflow: it affords a way to force air into the superior nasal vault and better contact with the olfactory mucosa.
In the human nasal cycle, Walliams and Eccles suggested a model for the central control of airflow patterns, in which in-phase and reciprocal airflow changes are demonstrated through the incorporation of a hypothalamic center and two brain-stem half centers.
What is abnormal Nasal Physiology?
Environmental allergies are the most prevalent causes of inflammation of nasal membranes, followed by inhaled irritants (e.g., cigarette smoke, various chemicals, perfumes, and other noxious odorants).
Nonallergic or vasomotor rhinitis is due to dysfunction of the autonomic nervous system or blood flow adjustment from iatrogenic or drug-related causes, Increase in blood flow or parasympathetic tone or decrease in the sympathetic tone increased congestion and drainage of the nasal cavity. Conversely, reduction of blood flow suppression of the parasympathetic system, and stimulation of asymptotic system decrease nasal congestion and discharge. Supplemental female hormones or Sonoma changes induced by pregnancy or menstruation may affect the nasal system. Any medication taken for hypertension or cardiac dysfunction may affect nasal physiology.
Nasal physiology also is affected by
anatomic deformities that may have varying effects on congestion, olfaction, and drainage. Enlarged turbinates and septal deviation can impact airflow into the nasal cavity, modifying it from a laminar pattern to a more turbulent pattern. Turbulent airflow produces further irritation to nasal membranes with a resultant rise in nasal drainage and congestion.
Nasal airway blocking from turbinate hypertrophy, secondary to upper respiratory illness (URI) allergic response, is the most common cause of tempory loss of small. The sense of smell is vital for the quality of life, specifically for safety, in cases of detecting smoke and other harmful odorants that could be fatal.
In the upper airways, paranasal sinuses, and nasal cavities are the mains source of nitric oxide (NO).However, the precise role of NO in nasal physiology is not entirely understood, the function is thought to be ciliary motility, host defense, and an improve ventilation-perfusion ratio in the lungs by auto-inhalation. Low NO concentration was observed in certain diseases, such as primary ciliary dyskinesia, cystic fibrosis, and acute and chronic maxillary sinusitis whereas high levels were detected in upper airway infection, allergic rhinitis, and nasal polyposis
Rhinomanometry strives to quantify nasal airflow and total nasal area during distinct nasal breathing. Differential pressure measurements are taken by placing a nasal catheter into the nasopharynx. Nasal resistance measurement evaluates all resistive portions of the nasal airway from nares within the front, to the nasopharynx and is susceptible to small augmentations in airway caliber. This method has been confirmed and is extremely useful for recording calibration in nasal patency due to pharmaceutical or surgical procedures. It is partly invasives, slow to execute and would need the patients help to complete.
Acoustic rhinometry is a newer method of evaluating the cross-sectional region of the nose and the volume of the nasal cavity through examination of incident and reflected sound while undergoing a short cessation of nasal breathing. This technique also has been confirmed and is helpful for recording changes in nasal caused surgical and pharmaceutical interventions. It is minimally invasives, quick to perform and requires no assistance from the patient
Rhinomanometry and acoustic rhinometry can be applied clinically to examine nasal patency in various circumstances. Either test may be employed for a general evaluation of nasal airflow and to compare pre morbid condition with changes that may happen after medical or surgical therapy. Additionally, these test can compare all passage for medical or surgical planning.