Detailed Analysis of Fiber Motion in Human Nasal Airways

Information on the fiber particle transport and deposition in human nasal airways is of great importance in inhalation toxicology study. Due to the complex interactions between the inhaled aerosol particles and human respiratory airways, the particles’ toxicity varies with their chemical composition, size, and shape. In the earlier computational study of fiber particle motion in human nasal cavities, overall deposition efficiency curves were evaluated and compared with the available experimental data. The majority of investigations were on micron-scale fiber particles, and the observed deposition fraction is strongly affected by fiber inertial impaction and the geometry of the cavity. The fiber characterization by its equivalent spheres is still not entirely fully understood. Limited existing evidence indicated that, when benchmarked by the impaction parameter, spherical particles tend to have a higher deposition fraction than that of the elongated fiber particles in the nasal cavity. More data is needed to elaborate on these observations and reveal the underlying physics. A more profound understanding of fiber transport in human airways may be obtained by comparing the fibrous particle deposition to that of the spherical particles. In this study, simulations of transport and deposition of elongated particles in a realistic human nasal cavity model for a steady laminar airflow rate were performed. FLUENT 19.2 was used to solve the airflow conditions. The elongated ellipsoidal particle transport and deposition were simulated using the coupled translational and rotational equations of motion. The hydrodynamic drag and torque, shear-induced lift, and gravitational force were included in the analysis. One-way coupling was assumed, and an in-house User Defined Function (UDF) was developed and was implemented into the ANSYS-FLUENT code for analyzing the fiber transport and deposition. The airflow field, the particle deposition efficiency, particle deposition pattern, and single-particle trajectories of fiber and sphere were analyzed and presented. The simulation results were compared with available experimental data and simulation results in the literature.

Nasotracheal intubation for airway management during anesthesia

Nasotracheal intubation is used as a basic method for airway management, along with orotracheal intubation under anesthesia and intensive care. It has become an effective alternative method to orotracheal intubation with increased benefits of offering better mobility and surgical field in oral and maxillofacial surgery and possibly in trauma and critically ill patients. Nasotracheal intubation is performed through a relatively narrow nasal cavity; therefore, additional precautions are needed. Accordingly, nasotracheal intubation methods have evolved over the years with accumulated clinical experience and improved instruments to facilitate safe intubation with reduced complications. Therefore, in this review article, we summarize the basic anatomy of the nasal airways to clarify the precautions, delineate the history and development of various methods and instruments, and describe the indications, contraindications, complications, and preventive methods of nasotracheal intubation.

Correlation of brachycephaly grade with level of exophthalmos, reduced airway passages and degree of dental malalignment’ in Persian cats

For many years, there has been a trend to breed cats with an increasing degree of brachycephalic head features, which are known to have a severe impact on the animals’ health and welfare. The direct relation between different grades of brachycephaly and their negative implications have not been researched in this species. The aim of this study was therefore to establish correlations between the different grades of brachycephaly and reduced upper respiratory airways, exophthalmos of the eye globes and malalignment of the teeth in Persian cats. Sixty-nine Persian cats of various skull dimensions and ten Domestic shorthair cats were recruited for the study. The cats’ skulls were examined using three-dimensional reconstructions created from Computed Tomography datasets. Brachycephaly was graded using established craniometric measurements (facial index, cranial index, skull index, craniofacial angle). The flow area of the nasal passageways at different locations, the amount of the eye globe not supported by the bony orbit and the axial deviation of the teeth were quantified and evaluated for a correlation with the grade of brachycephaly. The results of this study clearly show that increased grades of brachycephaly in Persian cats resulted in larger extra-orbital parts of the ocular bulbs. The brachycephalic skull dimension also resulted in a lower height of the naso-osseal aperture, while other areas of the nasal airways were not correlated with the severity of brachycephaly. Persian cats showed a significantly increased occurrence of premolar tooth displacement in the upper jaw with increasing brachycephaly grades. It was interesting to note that the measured values had a broad range and values of some individual Persian cats showed an overlap with those of Domestic shorthair cats.

Computational Investigation of The Exhalation Process with and Without Wearing a Protective Mask

This paper shows different simulations of airflow patterns for the human face during exhalation with and without wearing a protective mask. The nasal airways were defined based on biological anthropology and medicine instructions. A three-dimensional body-manikin of African athlete of 1.8 meters tall was employed to the expiration (exhalation) flow study using ANSYS-Fluent software. There were two different mask models included in the flow simulations and were manufactured by means of 3D-printing technology. The two manufactured masks were designed using SolidWorks software. The study was carried out four times during the exhalation process of a human wearing the two masks and without wearing them. The velocity magnitudes were significantly different while wearing the mask in comparison to the cases of not wearing it. The results demonstrate the capability of using 3D-printed masks as a replacement of the traditional medical masks (i.e., N95 and surgical masks) with retaining the same functions of the protective mask. Thus, based on the present study and due to the great shortage of surgical and medical masks availability locally and globally, the 3D-printed masks might be a temporary solution to limit the vast spread of contagious diseases like the dangerous COVID-19 outbreak.

Role for Mucin-5AC in Upper and Lower Airway Pathogenesis in Mice

Mucin-5AC (MUC5AC) is a major secreted mucin in pathogenic airways. To determine its role in mucus-related airway disorders, Muc5ac-deficient ( Muc5ac−/−) and wild-type ( Muc5ac+/+) mice were compared in bleomycin-induced pulmonary fibrosis, respiratory syncytial virus (RSV) disease, and ozone toxicity. Significantly greater inflammation and fibrosis by bleomycin were developed in Muc5ac−/− lungs compared to Muc5ac+/+ lungs. More severe mucous cell metaplasia in fibrotic Muc5ac−/− lungs coincided with bronchial Muc2, Muc4, and Muc5b overexpression. Airway RSV replication was higher in Muc5ac−/− than in Muc5ac+/+ during early infection. RSV-caused pulmonary epithelial death, bronchial smooth muscle thickening, and syncytia formation were more severe in Muc5ac−/− compared to Muc5ac+/+. Nasal septal damage and subepithelial mucoserous gland enrichment by RSV were greater in Muc5ac−/− than in Muc5ac+/+. Ozone exposure developed more severe nasal airway injury accompanying submucosal gland hyperplasia and pulmonary proliferation in Muc5ac−/− than in Muc5ac+/+. Ozone caused periodic acid-Schiff-positive secretion only in Muc5ac−/− nasal airways. Lung E-cadherin level was relatively lower in Muc5ac−/− than in Muc5ac+/+ basally and after bleomycin, RSV, and ozone exposure. Results indicate that MUC5AC is an essential mucosal component in acute phase airway injury protection. Subepithelial gland hyperplasia and adaptive increase of other epithelial mucins may compensate airway defense in Muc5ac−/− mice.