Discussion
The present study focused on relationships between nasal morphological
variations due to inter- and intra-racial differences and gender, which
differs from previously published studies by our group investigating
nasal morphological variations.2, 18 Unlike this study
that categorizes nasal index by subjects’ race/ethnicity with gender,
and gender separately; Patki and Frank-Ito2 explored
the relationship between nasal index and CFD simulated airflow-related
variables, such as nasal resistance, wall shear stress, and heat flux.
Although Keeler et al.18 modeled deposition patterns
of individuals across the same four race/ethnic groups as the present
study, as well as briefly reported results of SAV ratio, nasal
resistance and nasal index across races/ethnicities; the present student
conducted an in-depth analysis of both anatomical and airflow-related
variables in the same race/ethnic groups with gender as a factor.
Additionally, Keeler et al.18 included the paranasal
sinuses in their CFD models while the present study excluded the
paranasal sinuses are they have negligible effects on physiological
functions pertaining to the main nasal cavities.
Nasal index results are in agreement with reports on climate-related
variation in human nose, suggesting that individuals that evolved from
colder and drier climates tended to have smaller nasal index than
individuals from warmer and more humid climates.2, 12,
18, 19 Results in this study pertaining to nasal index and gender are
consistent with those previously reported by Ravichandran et
al.20 In their paper, Ravichandran and colleagues
found that nasal index is a reliable parameter for the estimation of
gender difference, noting that the average value of nasal indices of
South Indian males was greater than South Indian
females.20 Additionally, in a study examining the
nasal index of the Kosovo Albanian population, males had a significantly
higher nasal index than females (p <
0.001).21 While similar conclusions can be made with
the Caucasian population from the present study, it should be noted that
the difference in median nasal index between Caucasian males and females
was 0.66. Additionally, when comparing nasal index and gender by race,
East Asian and Black females had larger average nasal index than their
male counterparts.
The current literature is sparse regarding the relationship between
nasal resistance and race/ethnicity. Keeler et al.18reported that average nasal resistance for African Americans and
Caucasians were lowest and highest, respectively. Other studies have
reported no significant differences in nasal resistance between African
descents and Caucasians.19, 22, 23 Babatola measured
nasal resistance of African descents from Nigeria and concluded that
nasal resistance in this population was similar to those of Caucasians
and Asians.22 Calhoun et al. and Ohki et
al.19, 23 also arrived at similar conclusions in their
studies. Our results suggest that median nasal resistance was highest
among Caucasians, followed by Blacks before Latinos, and East Asians had
the lowest median nasal resistance values. Nonetheless, it should be
noted that the IQR values for Blacks and East Asians were particularly
larger than those of Caucasians and Latinos, implying there could be
possible overlap among the groups, which may indicate non-significant
differences among groups.
Our findings indicate females have a larger nasal resistance than males.
This trend was seen within every race except for Caucasians when
comparing between nasal resistance and race and gender. A study
conducted by Warren et al.24 revealed no significant
difference in resistances for males and females with normal nasal
anatomy. However, Ren et al.25 reported that mean
nasal resistance in males were significantly lower than females among a
cohort of healthy subjects in China.
The main limitation from the present study pertains to our relatively
small sample size. Although there were 16 subjects, each race had 4
subjects, and after further stratification by race and gender, there
were 2 subjects per group. In conclusion, this study investigated the
relationships between normal nasal morphological variations due to
inter- and intra-racial and gender differences in subject-specific nasal
airway models from 16 subjects across 4 racial groups. Findings from the
present work indicate that there is an association between normal nasal
anatomical variabilities across race and gender. However, these
variabilities may not discriminate proper functioning of the nasal
cavity across race and gender.