Introduction
The normal human nose is distinguished by common inter- and intra-individual nasal morphological variations. These variations such as nasal cycle, nasal vestibule phenotypes, and nasal index can influence objective description of normal nasal airflow profile.1-4 Briefly, the asymmetry of nasal airflow as characterized by a random, reciprocal shift in nasal patency due to temporal periods of congestion and decongestion of the mucosa in both nasal passages is described as nasal cycle.1 Prior studies reported between 21% and 80% of individuals experience some aspect of nasal cycling.3, 5, 6
Ramprasad and Frank-Ito7 identified another feature of natural variation in the nasal anatomy based on nasal vestibule morphological shapes, which were classified as Notched, Standard, and Elongated. Reported findings suggest global airflow patterns and resistance in the nasal cavity were unaffected by the different morphological shapes, but local airflow resistance and air conditioning performance were found to be greatly impacted by these morphological variations.3, 7 Consequently, it was postulated that the manifestation of these distinct normal nasal vestibule phenotypes may be associated with the fact that the human nasal airway naturally response to localized constrictions by inducing corresponding physiological response on other regions of the airway in order to maintain natural ventilation conditions.3, 7, 8
Variations in nasal morphology is also thought to have been due to human adaptation to diverse climatic environments.2, 9-11Changes in nasal shape reflect the conditions for respiration in an environment as adaptations were made in order to provide more efficient conditions to maximize respiration.2, 9 These differences in human noses due to geographic adaptations are often characterized by nasal index.7, 12, 13 A systematic review study performed by Leong and Eccles showed no consistent evidence supporting the idea that differences in nasal shape and size based on ethnic descent influence physiology.12
Although the predicted link between race and nasal morphology is supported by anthropological studies recording relationships between climate and nasal function, more studies need to be done to understand how gender differences within and between races influence nasal physiology. Little is known on the associations of nasal anatomy and function based on race and gender. Nonetheless, it has been established that males exhibit larger nasal cavities volumes and longer and narrower nasal floors than females of a similar body size.4, 14, 15
Thus, the purpose of the present study is to use computational modeling to investigate additional relationships between nasal morphological variations due to inter- and intra-racial differences and gender.