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.