Physiology and pathophysiology of nasal breathing

Abstract

The respiratory function of the nose is to warm, humidify, and clean the inhaled air. The basic condition for that is an undisturbed nasal air passage. The physical knowledge to understand the different causes for an increased nasal resistance is reported. From an air-dynamic point of view, the nasal stream canal has a very complicated architectural structure which is a requirement for such an enormous task like the function of respiration. For the exchange of warm-energy and humidity through convection and radiation, it is advantageous to have a narrow flow channel (slit space), since this configuration facilitates the biophysical process. The air needs a sufficient contact with the mucosa. The nasal airstream must be distributed over the entire mucosal surface in the functional area of the nasal cavum, that is, the region of the turbinates. In this region, contact time between the air and the mucosa must be as long as possible, and formation of turbulent flow and its regulation corresponding to the phases of the nasal cycle are necessary. Responsible for these requirements is the inflow area, which consists in inspiratory flow direction of the vestibule, the internal ostium nasi, and the anterior part of the cavum. The knowledge on the correlation of the structure and respiratory function of the nose, particularly significant for a rhinosurgeon, is discussed. Finally, rhinosurgical consequences from these physiological and pathophysiological knowledge are summarized.