12 research outputs found
Assessing Ecogeographical Variation in the Nasal Passages Utilizing 3D Semilandmarks
No full textPrior research has shown strong statistical relationships between geographically-patterned variation in nasal skeletal morphology and global climatic conditions. Specifically, the nasal skeletons of individuals indigenous to cold-dry environments tend to be longer, taller, and especially narrower, than those from hot-humid environments. As the nasal passages heat and humidify inspired air for entry into the lungs, this morphological patterning is believed to reflect the specific air-conditioning demands of different climates. However, while it is widely assumed the morphology of the nasal skeleton accurately reflects that of the functional (soft-tissue) nasal passages, the existence of ecogeographic variation in the three-dimensional (3D) nasal soft tissues has yet to be empirically demonstrated. This study investigates 3D shape variation in decongested soft-tissue nasal passages of individuals ancestrally derived from cold-dry (CD) and hot-humid (HH) environments (n=20). Using 3D Slicer and Avizo, a total of 260 semilandmarks were collected from the decongested nasal passages of Each individual. General Procrustes Analysis (GPA) was then used to align the semilandmark configurations of all 20 individuals and a Principal Component Analysis (PCA) was subsequently performed using the Geomorph package in R. Our results indicate PC1 (19.13%) largely contrasts CD individuals with positive PC1 scores (relatively narrower nasal passages) from HH individuals with negative PC1 scores (relatively wider nasal passages). These results generally conform to morphological expectations, suggesting a general concordance between skeletal and decongested soft-tissue nasal anatomy. This study thus provides the impetus for future research investigating the relationship between ecogeographic variation in nasal soft-tissue anatomy and air-conditioning physiology
Deconstructing adaptation in the human nasal airway: An iterative assessment of intranasal airflow and nasal morphology in two and three dimensions.
No full textINTRODUCTION: Nasal geometries have been established as being strongly correlated with climate. In cold-dry climates geometries tend to be tall/narrow, while in hot-humid climates geometries are short/broad. This pattern suggests that taller/narrower nasal airways functionally enhance intranasal air-conditioning (i.e., heat and moisture transfers) by increasing nasal surface area relative to intranasal volume, but this hypothesis has not been empirically tested. METHODS: This study employs 3D models of decongested nasal passages generated from cranial CT scans of individuals of predominantly European (5 males, 6 females) and African (5 males, 5 females) ancestry to directly investigate proposed form-function relationships. Each 3D model then underwent an airflow simulation using computational fluid dynamics to collect measurements of intranasal air temperature, humidity, and airflow velocity across consecutive planes of the 3D models. Morphological measurements of nasal passage area, perimeter, and circularity (i.e., shape) were subsequently collected from the same cross-sectional planes for which airflow measurements were collected. spanning the length of the passage. Multivariate regressions were then performed to assess relationships between morphological and physiological variables at each 2D plane and cumulatively across the entire 3D passage. RESULTS: Regression results indicate that nasal passage morphology, particularly turbinate chamber circularity was significantly associated with intranasal air-conditioning (R2 =0.54, p=0.029). Consistent with proposed hypotheses, individuals with taller/narrower (i.e., less circular) turbinate chamber cross-sectional shapes were found to be associated with higher total inspiratory heat and moisture transfers. CONCLUSIONS: This study provides support for climatic pressures selecting for intranasal air conditioning promoted adaptive changes in nasal morphology during human evolution, likely accounting for the observance of taller/narrower nasal passages in Pleistocene and Holocene Homo sapiens following migrations into colder and/or drier environments.Texas Center for Health Disparities Grant #RF00241 via NIMHD #5U54MD006882-10
Every breath you take: Experimentally investigating respiratory responses to hot environments
No full textResearch Appreciation Day Award Winner - School of Biomedical Sciences, 2024 Department of Physiology & Anatomy (Structural Anatomy & Rehabilitation Sciences) Award - 2nd PlaceThe human body loses heat to the environment through two mechanisms: the skin and the respiratory system. Accordingly, it has previously been hypothesized that respiration may play an important role in overall thermoregulatory responses to heat stress. However, previous studies investigating respiratory responses to heat have generally failed to account for variation in humidity levels seen across hot environments (i.e., hot-humid vs. hot-dry conditions). Thus, the goal of this study was to experimentally test for potential differences in respiratory responses to heat stress given variation in air humidity. A mixed-sex sample of human volunteers (5 females, 6 males) were subjected to three different climatic conditions: room temperature (22°C, 50% relative humidity (RH)), hot-dry (44°C, 15% RH), and hot-humid (37°C, 85% RH).Test subjects were exposed to each climatic condition for 45 minutes, with metabolic and respiratory data collected for 30 minutes using a wearable COSMED K-5 metabolic system. Respiratory frequency (Rf, breaths/minute) and oxygen consumption (VO2, ml/minute)were assessed. Results of a repeated-measures ANOVA found a statistically significant difference in Rf values between the climatic conditions (F=5.05, p=0.017). Subsequent Tukey-Kramer multiple-comparison post-hoc test results indicate that participants exhibited significantly higher Rf values in the hot-dry condition (mean=17.498) compared to the room temperature (mean=15.859)and hot-humid (mean=15.764) conditions. In contrast, no significant differences for VO2 consumption between the three climatic conditions (F=2.33, p=0.123) were found. These results indicate that in the hot-dry climatic condition, participants breathe more frequently without increasing the total amount of air inspired (i.e., taking more frequent but shallower breaths). These results are largely consistent with findings of previous studies that have demonstrated similar physiological responses to heat stress. Furthermore, our study highlights the existence of differential respiratory responses in hot-dry vs. hot-humid conditions, suggesting that humidity may play an important role in mediating respiratory responses to heat stress. Additional research into the impacts of humidity on respiratory function is thus warranted.National Science Foundation #2020506 (Cowgill), #2020096 (Ocobock), #2203808 (Cho), #2020715 (Maddux
Assessment of digit skin temperatures via infrared thermography under different climatic conditions.
No full textThe responsiveness of the manual/pedal digits (i.e., finger/toes) to temperature changes makes them valuable indicators of thermoregulatory function. Further, while infrared thermography is used in many medical settings, its utility in assessing acute changes in digit skin temperatures remains poorly established. Accordingly, this research investigated the use of forward-looking infrared (FLIR) imaging as a methodological tool for analyzing digital skin temperatures across varying climatic conditions. A Teledyne FLIR E76 camera and associated FLIR Studio software were used to assess peripheral digit skin temperatures in a sample of 25 living human subjects (12 female, 13 male). Images of each hand and foot were captured every 5 minutes over a 45-minute period during exposure to four controlled climatic conditions in an environmental chamber. These experimental conditions included a control (22°C and 50% humidity), hot-humid (37°C and 85% humidity), hot-dry (44°C and 15% humidity), and cold-dry (5°C and 80% humidity) exposures. All images were taken at a perpendicular angle from the skin surface at a distance of 0.45 mm, as measured using the camera’s laser-guided range finder function. Baseline images were similarly taken during a preliminary rest period prior to each experimental exposure. This resulted in a total of 2,200 images collected from the left hand and left foot of the 25 participants. Following theoretical expectations, preliminary findings indicate peripheral digit temperatures predictably decrease during the cold-dry exposure, while the hot-dry and hot-humid exposures induce increases in digit temperatures. These preliminary results suggest that infrared thermography likely provides an expedient mechanism for accurately assessing peripheral skin temperatures in humans under different climatic conditions. Infrared thermography may thus have valuable applications for assessing thermoregulatory function in both clinical and research settings.National Science Foundation #2020506 (Cowgill), #2020096 (Ocobock), #2203808 (Cho), #2020715 (Maddux
Evaluating philtrum-to-tragus distance as an external predictor of nasal passage dimensions: A computed tomography (CT) approach
No full textResearch Appreciation Day Award Winner - School of Biomedical Sciences, 2024 Department of Physiology & Anatomy (Structural Anatomy & Rehabilitation Sciences) Award - 1st PlaceAccurate quantification of nasopharyngeal temperature requires the placement of a flexible intranasal probe into the upper or mid-nasopharynx. Yet, without guidance from medical imaging, data shows that in practice less than half of nasopharyngeal temperature probes are optimally positioned. Still, previous studies have suggested that the distance between the philtrum (external nose) to tragus (external ear) provides a reliable predictor of internal nasal passage dimensions. However, previous attempts to verify the accuracy of this external proxy have returned equivocal results. Accordingly, this study employed measurements collected from CT scans of 11 living participants (4 female, 7 male) to assess associations between external philtrum-tragus length and internal lengths of the nasal cavity, nasopharynx, and total nasal passage (i.e., cavity + pharynx). Results show statistically significant correlations between philtrum-tragus length and internal measurements of nasal cavity (r=0.412, p=0.033) and total nasal passage (r=0.502, p=0.015) length. In contrast, no significant correlation was identified between philtrum-tragus length and nasopharynx length (r=0.110, p=0.320). Despite the small size of the study sample, these suggest that philtrum-tragus length can provide insights for estimating internal dimensions relating to the location of the end of nasal cavity (i.e., choanal aperture) and the posterior wall of nasopharynx. Thus, this external measurement may enhance the accuracy of intranasal probe placement, especially when medical imaging data (i.e., radiographs, CT, MRI) are not available for guidance. Accordingly, additional investigation into the applied utility of philtrum-tragus length with larger sample sizes appears warranted.National Science Foundation #2020506 (Cowgill), #2020096 (Ocobock), #2203808 (Cho), #2020715 (Maddux). North Texas Regional IRB: #1875793-1
Investigating Associations Between Asthma and Nasal Abnormalities: A Computed Tomography (CT) Approach
No full textPurpose: Asthma affects over 300 million people worldwide and 3,500 people suffer asthma related deaths each year. Although there is no clear cause of asthma, approximately 90% of asthmatics suffer from cold/exercise induced bronchoconstriction, a symptom triggered by the inhalation of cold and/or dry air. As the nasal passages account for most of the heat and moisture transferred to inspired air during respiration, anatomical variation in nasal morphology may contribute to asthma development. While the existence of nasal anatomical variants is well documented, little is known about the prevalence of such variants among asthmatics. Methods: Accordingly, this study sought to investigate potential associations between asthma and three common nasal anatomical variants: septal deviations, concha bullosa, and paradoxical turbinate. This study analyzed Computer Topography (CT) scans of a diverse, mixed sex sample (n=242) from the New Mexico Decedent Image Database (NMDID). The asthmatic individuals (n= 120) were identified through associated medical records and compared to a control sample of non-asthmatics (n = 122). CT scans were analyzed using Avizo permitting qualitative coding of each anatomical variant for presence and type. Chi-square tests of independence were then used to test for differences in variant prevalence between the asthmatic and control samples. Results: The results of our study show significantly higher prevalence of concha bullosa in asthmatics compared to control individuals (χ2= 5.87, p=0.015), with 70.0% asthmatics exhibiting at least one pneumatized turbinate compared to only 54.9% of control individuals. Conclusions: This result suggests a potential relationship between the presence of conchae bullosa and asthma, possibly due to this variant negatively influencing intranasal air-conditioning capabilities. Future work employing computational fluid dynamics (CFD) analyses may be able to further elucidate the influence concha bullosa have on nasal passage air flow and conditioning. Such work could provide important insights into the role nasal anatomy may play in asthma prevalence and severity. This project was supported by Texas Center for Health Disparities grants RF00241 & RI40241Texas Center for Health Disparities grants RF00241 & RI4024
Ancestry‐based variation in maxillary sinus anatomy: Implications for health disparities in sinonasal disease
No full textExperimentally Reevaluating Respiratory Contributions to Total Body Heat Loss in Human Thermoregulation: A Pilot Study
No full textThere are generally two anatomical systems in which heat is exchanged between the human body and the surrounding environment: the integument (skin) and the respiratory system. The skin is commonly reported to account for about 90% of total body heat loss to the environment, with respiration contributing the remaining 10%. Yet, variation in ambient air conditions (e.g., temperature, relative humidity) can alter the exact ratio of skin vs. respiratory heat loss. Accordingly, this pilot study sought to experimentally quantify the percentage of heat loss due to respiration under different temperature exposures. Five human volunteers (2 females, 3 males) were exposed to four climatic conditions: room temperature (22°C, 50% relative humidity (RH)), cold-dry (5°C, 80% RH), hot-dry (44°C, 15% RH), and hot-humid (37°C, 85% RH). Each exposure lasted for 45 minutes, with 30 minutes dedicated to collecting metabolic data and 15 minutes for respiratory data. The percentage of respiratory heat losses under the four conditions were assessed using established heat balance equations. Repeated-measures ANOVA revealed statistically significant differences in the percentage of respiratory heat loss between the conditions (p<0.001). Subsequent Tukey-Kramer post-hoc analysis test showed that the percentage of respiratory heat loss was significantly lower in the hot-humid condition compared to room temperature (p=0.001), cold-dry (p=0.007), and hot-dry (p<0.001) conditions. Importantly, these findings suggest that in hot-humid conditions the respiratory system likely still acts as a mechanism for shedding heat, somewhat offsetting a reduced capacity for heat loss through the skin, and thus potentially helping to minimize total heat gain from the environment. Moreover, these results provide evidence of differences in skin vs. respiratory contributions to total heat losses in different climatic conditions, thus underscoring the urgency to reassess conventional models in light of varying environmental conditions
Experimentally investigating sex-based differences in thermoregulatory responses to cold environments in human subjects
No full textDespite sex-based differences in human body size and composition, most ecogeographic research tends to focus on male subjects, with limited female representation. Accordingly, this study investigated thermoregulatory responses in core and peripheral body temperatures in both male (n=12) and female (n=12) human subjects exposed to room temperature (RT = 22°C, 50% relative humidity) and cold-dry (CD = 5°C, 80% RH) conditions for 45 minutes in a climate chamber. Core temperature was measured continuously via ingestible thermometer capsules while peripheral skin temperature was measured on the dorsal aspect of the left hand (LH) via an iButton surface thermometer. Both were averaged across 5-minute intervals. Performing a two-way repeated measures ANOVA of the RT exposure indicated a statistically significant core temperature decrease over time (F=3.23, p=0.002) and between the sexes (F=2.63, p=0.010), while LH skin temperature significantly decreased over time (F=318.18, p<0.001) without sex differences (F=0.18, p=0.993). During the CD exposure, there was a significant increase in core temperature over time (F=9.91, p<0.001) with no sex differences (F=1.10, p=0.368), along with a significant decrease in LH skin temperature over time (F=448.18, p<0.001) and between the sexes (F=3.17, p=0.002). Females consistently exhibited lower LH temperatures (20.47°C) than males (21.31°C) in the cold. Although both sexes followed the same general increase in core temperature in the cold, males had a larger change than females between the five to ten minute (0.06°C) and forty to forty-five minute intervals (0.10°C). Furthermore, females exhibited a rise and fall in their core temperature in RT, while males only had a decrease in core temperature throughout the exposure. These results suggest that both sexes physiologically respond to cold exposure by protecting core body temperature at the expense of peripheral skin temperatures and may reflect differences in hand size and composition dynamics. Additional research with a larger sample size and evaluation of additional factors may help to clarify this issue
INVESTIGATING VARIATION IN HUMAN BODY COMPOSITION: A COMPARISON OF CT AND DEXA IMAGING MODALITIES
No full textAnthropologists have long recognized that differences in body composition influence how humans thermoregulate during exposure to different climatic conditions. Yet, research into the role of body composition in thermoregulation has been limited by a lack of methodological options for accurately quantifying different types of internal body tissues (i.e., bone, muscle, adipose). The development of medical imaging technologies such as computed tomography (CT) and dual energy x-ray absorptiometry (DEXA) has provided new approaches for accurately assessing the amount and distribution of various types of tissue within the body. However, the comparability of these two imaging modalities in assessing body composition has not been rigorously investigated. Accordingly, this project will employ matching sets of whole-body CT scans and whole-body DEXA scans collected from the same research subjects to evaluate the ability of each modality to quantify the absolute and relative amount of different tissue types. Initial results indicate that DEXA and CT return similar values for lean mass (DEXA = 29.94 kg, CT = 29.75 kg) differing by approximately 0.61%. In contrast, differences in fat mass values (DEXA = 10.57 kg, CT = 9.31 kg) are comparatively greater at 11.88%. Further research is needed to determine why the two modalities differ so substantially in their assessments of adiposity
