Aging effects on airflow dynamics and lung function in human bronchioles

Background and objective The mortality rate for patients requiring mechanical ventilation is about 35% and this rate increases to about 53% for the elderly. In general, with increasing age, the dynamic lung function and respiratory mechanics are compromised, and several experiments are being conducted to estimate these changes and understand the underlying mechanisms to better treat elderly patients. Materials and methods Human tracheobronchial (G1 ~ G9), bronchioles (G10 ~ G22) and alveolar sacs (G23) geometric models were developed based on reported anatomical dimensions for a 50 and an 80-year-old subject. The aged model was developed by altering the geometry and material properties of the model developed for the 50-year-old. Computational simulations using coupled fluid-solid analysis were performed for geometric models of bronchioles and alveolar sacs under mechanical ventilation to estimate the airflow and lung function characteristics. Findings The airway mechanical characteristics decreased with aging, specifically a 38% pressure drop was observed for the 80-year-old as compared to the 50-year-old. The shear stress on airway walls increased with aging and the highest shear stress was observed in the 80-year-old during inhalation. A 50% increase in peak strain was observed for the 80-year-old as compared to the 50-year-old during exhalation. The simulation results indicate that there is a 41% increase in lung compliance and a 35%-50% change in airway mechanical characteristics for the 80-year-old in comparison to the 50-year-old. Overall, the airway mechanical characteristics as well as lung function are compromised due to aging. Conclusion Our study demonstrates and quantifies the effects of aging on the airflow dynamics and lung capacity. These changes in the aging lung are important considerations for mechanical ventilation parameters in elderly patients. Realistic geometry and material properties need to be included in the computational models in future studies

Correlation of nasal morphology to air-conditioning and clearance function

Nasal morphology plays an important functional role in the maintenance of upper airway health. Identification of functional regions, based on morphological attributes, assists in correlating location to primary purpose. The effects of morphological variation on heat and water mass transport in congested and patent nasal airways were investigated by examining nasal cross-sectional MRI images from 8 healthy subjects. This research confirms the previous identification of functional air-conditioning regions within the nose. The first is the anterior region where the morphology prevents over-stressing of tissue heat and fluid supply near the nares. The second is the mid region where low flow velocity favours olfaction and particle deposition. The third is the posterior region which demonstrates an increase in heat and water mass flux coefficients to compensate for rising air humidity and temperature. Factors identified within the congested airway that favour enhanced mucocillary clearance were also identified

Deposition of inhaled particles in a symptomatic asthmatic human respiratory tract

Inhalation medicinal aerosol and biological aerosol risk assessment are the current motivation for deposition models to be developed. Inhalation aerosols have been around for many years for the treatment of asthma and other respiratory ailments in which the aerosols targeted the upper airways. Current research is focused to target the alveolar sacs due to their vast surface area for drug and gene delivery. Targeting the alveolar sacs Corkery (2000) requires a slow and deep breathing pattern for maximum deposition at the alveolar units. Also the particles must be fairly small (1-3 µm) to avoid deposition by impaction. Gautam et al. (2003), states that aerosol inhalation therapy has the following advantages: a greater surface area to absorb and sediment drugs and genes, the absorption is immediate, there is low systemic toxicity, and the delivery of the drug is a non-invasive procedure. The authors\u27 foresee inhalation medicine coming into practice in the near future. A proven and effective case is the delivery of insulin formulation via an inhalation device. Through inhalation of insulin, patients will not have to tolerate the constant injection of insulin thus improving their obedience in taking their insulin devotedly. Biological aerosol risk assessment is another topic that warrants deposition modeling in the lung. According to Douwes et al. (2003), the occupational environment is producing potent bio-aerosols that lead to infectious diseases, acute toxic effects, allergies and cancer within people exposed to these aerosols. The authors cite examples of industries that are producing these bio-aerosols, such as the cotton industry, farming, waste and compost industry, and the automotive industry, etc. The main focus is to assess these industries and the bio-aerosols that they produce in a quantitative way. The authors\u27 note that these assessments of bio-aerosols have mainly been qualitative or semi-quantitative at best in research and stress that there needs to be more quantitative analysis on the bio-aerosol production and risk assessment, so that proper care and caution can be taken in the future. There are significant gaps in information completeness concerning modeling particulate deposition in diseased lungs. The gaps in information stem from inaccurate or vague results in quantification of the geometric and dynamic parameters that deviate respiratory ailments from a normal individual, also, there is lack of computer models that describe the different respiratory ailments. This former idea is a necessity for advancement of a particular problem. Computer models reflect a compilation of knowledge on a particular subject that produces an end result that can be verified readily by field tests. The goal of this research was two-fold. First objective were to perform a literature search that summarized the current literature on experimental deposition data, pulmonary function test data, and airway modifications due to asthma and COPD. Second, the separate modules of the computer routine will predict deposition of inhaled particles of varying sizes in a symptomatic asthmatic case (COPD data from literature did not yield enough quantitative data to make modifications). The inputs consist of breathing patterns, lung geometry, and particle concentration and distribution. The inputs are then used in conservation equations and deposition mechanisms to describe how the particles will move throughout the region. Outputs are in the form of mass deposition fraction [%], deposition efficiency, and average deposition per generation. Overall the model was successful in predicting the intuition one would have in comparing deposition amounts in asthma versus healthy cases. There was more total deposition of particles for every particle size in the symptomatic asthma cases relative to the normal case specifically as particle size increased. The increased deposition was primarily due to the impaction deposition mechanism for larger particles sizes, specifically 5 µm and 10 µm particle sizes. This work was supported by a grant from the Phillip Morris External Research Foundation

Particle depositions in multi stage liquid impinger as simplified lung model using computational fluid dynamic

Inhaled medication is typically used to treat obstructive pulmonary disease and systemic diseases. The effectiveness of pulmonary drug delivery depends on the amount of drug deposited beyond the oropharyngeal region, the place where the deposition and the uniform distribution occurred. In this study, the performance of multistage liquid impinger (MSLI) simplified model which imitates the physiological lung in delivering the drug was analyzed. In order to achieve this main aim, the airflow patterns and particle depositions efficiency were evaluated in MSLI simplified model using computational fluid dynamic of COMSOL® software. The particle deposition efficiency is studied by varying flowrates (30.0 L/min, 60.0 L/min and 100.0 L/min) and particle sizes (0.1, 1.0, 3.0, 5.0, 10.0 pm) of salbutamol sulphate (density 20.0 kg/m3). The highest particle deposition occurred at flowrate 100.0 L/min and particle size of 1.0 pm as the deposition yield was 15.55% compared to flowrate 60 L/min and 30 L/min which were 10.50% and 3.09% respectively. Previous studies claimed that higher inhalation flowrate generated dispersion forces for sufficient inhalation flowrate thus enhanced higher deposition efficiency. The paired-samples T-test shows there were significant different (t= -15.400, df= 4, p <0.05) in the performance of particle depositions in MSLI simplified model with different flow rates (60.0 L/min and 100.0 L/min). Thus, the efficient fine particle deposition was significantly contributed by higher flowrate. This study also revealed that particle size ranges from 1.0 to 3.0 pm was the most suitable for inhalation treatment. Smaller particle size less than 1.0 pm was not suitable as it tended to exhale before it deposit of while larger particle (more than 5.0 pm) was not suitable for inhaled drug. In conclusion, vigorous air flow pattern promotes higher particle deposition. For efficient fine particle depositions, it is important to consider not only the particle size distribution, but also the flowrate as vital aerosol transportation agent. Statistical analysis, two-way ANOVA indicated that there was a statistically significant interaction between the effect of flowrate and particle size on particle deposition efficiency, F (8, 30)=5.857, p=0.00

Advancements in veterinary medicine: the use of Flowgy for nasal airflow simulation and surgical predictions in big felids (a case study in lions)

Flowgy is a semi-automated tool designed to simulate airflow across the nasal passage and detect airflow alterations in humans. In this study, we tested the use and accuracy of Flowgy in non-human vertebrates, using large felids as the study group. Understanding the dynamics of nasal airflow in large felids such as lions (Panthera leo) is crucial for their health and conservation. Therefore, we simulated airflow during inspiration through the nasal passage in three lions (Panthera leo), two of which were siblings (specimens ZPB_PL_002 and ZPB_PL_003), without breathing obstructions. However, one of the specimens (ZPB_PL_001) exhibited a slight obstruction in the nasal vestibule, which precluded the specimen from breathing efficiently. Computed tomography (CT) scans of each specimen were obtained to create detailed three-dimensional models of the nasal passage. These models were then imported into Flowgy to simulate the airflow dynamics. Virtual surgery was performed on ZPB_PL_001 to remove the obstruction and re-simulate the airflow. In parallel, we simulated the respiration of the two sibling specimens and performed an obstructive operation followed by an operation to remove the obstruction at the same level and under the same conditions as the original specimen (ZPB_PL_001). Thus, we obtained a pattern of precision for the operation by having two comparable replicas with the obstructed and operated specimens. The simulations revealed consistent airflow patterns in the healthy specimens, demonstrating the accuracy of Flowgy. The originally obstructed specimen and two artificially obstructed specimens showed a significant reduction in airflow through the right nostril, which was restored after virtual surgery. Postoperative simulation indicated an improvement of &gt;100% in respiratory function. Additionally, the temperature and humidity profiles within the nostrils showed marked improvements after surgery. These findings underscore the potential of Flowgy in simulating nasal airflow and predicting the outcomes of surgical interventions in large felids. This could aid in the early detection of respiratory diseases and inform clinical decision-making, contributing to improved veterinary care and conservation efforts. However, further research is needed to validate these findings in other species and explore the potential of integrating Flowgy with other diagnostic and treatment tools in veterinary medicine

Numerical modelling of micron particle inhalation in a realistic nasal airway with pediatric adenoid hypertrophy: A virtual comparison between pre- and postoperative models

Adenoid hypertrophy (AH) is an obstructive condition due to enlarged adenoids, causing mouth breathing, nasal blockage, snoring and/or restless sleep. While reliable diagnostic techniques, such as lateral soft tissue x-ray imaging or flexible nasopharyngoscopy, have been widely adopted in general practice, the actual impact of airway obstruction on nasal airflow and inhalation exposure to drug aerosols remains largely unknown. In this study, the effects of adenoid hypertrophy on airflow and micron particle inhalation exposure characteristics were analysed by virtually comparing pre- and postoperative models based on a realistic 3-year-old nasal airway with AH. More specifically, detailed comparison focused on anatomical shape variations, overall airflow and olfactory ventilation, associated particle deposition in overall and local regions were conducted. Our results indicate that the enlarged adenoid tissue can significantly alter the airflow fields. By virtually removing the enlarged tissue and restoring the airway, peak velocity and wall shear stress were restored, and olfactory ventilation was considerably improved (with a 16∼63% improvement in terms of local ventilation speed). Furthermore, particle deposition results revealed that nasal airway with AH exhibits higher particle filtration tendency with densely packed deposition hot spots being observed along the floor region and enlarged adenoid tissue area. While for the postoperative model, the deposition curve was shifted to the right. The local deposition efficiency results demonstrated that more particles with larger inertia can be delivered to the targeted affected area following Adenoidectomy (Adenoid Removal). Research findings are expected to provide scientific evidence for adenoidectomy planning and aerosol therapy following Adenoidectomy, which can substantially improve present clinical treatment outcomes.</p

Biomechanical Models of Human Upper and Tracheal Airway Functionality

The respiratory tract, in other words, the airway, is the primary airflow path for several physiological activities such as coughing, breathing, and sneezing. Diseases can impact airway functionality through various means including cancer of the head and neck, Neurological disorders such as Parkinson\u27s disease, and sleep disorders and all of which are considered in this study. In this dissertation, numerical modeling techniques were used to simulate three distinct airway diseases: a weak cough leading to aspiration, upper airway patency in obstructive sleep apnea, and tongue cancer in swallow disorders. The work described in this dissertation, therefore, divided into three biomechanical models, of which fluid and particulate dynamics model of cough is the first. Cough is an airway protective mechanism, which results from a coordinated series of respiratory, laryngeal, and pharyngeal muscle activity. Patients with diminished upper airway protection often exhibit cough impairment resulting in aspiration pneumonia. Computational Fluid Dynamics (CFD) technique was used to simulate airflow and penetrant behavior in the airway geometry reconstructed from Computed Tomography (CT) images acquired from participants. The second study describes Obstructive Sleep Apnea (OSA) and the effects of dilator muscular activation on the human retro-lingual airway in OSA. Computations were performed for the inspiration stage of the breathing cycle, utilizing a fluid-structure interaction (FSI) method to couple structural deformation with airflow dynamics. The spatiotemporal deformation of the structures surrounding the airway wall was predicted and found to be in general agreement with observed changes in luminal opening and the distribution of airflow from upright to supine posture. The third study describes the effects of cancer of the tongue base on tongue motion during swallow. A three-dimensional biomechanical model was developed and used to calculate the spatiotemporal deformation of the tongue under a sequence of movements which simulate the oral stage of swallow