Shigeru Ishikawa

Flow Mechanisms in the Human Olfactory Groove Numerical Simulation of Nasal Physiological Respiration During Inspiration, Expiration, and Sniffing

OBJECTIVES To visualize the velocity and the streamline of physiological unsteady nasal flow and sniffing using the computational fluid dynamics method and to compare the inspiratory phase, expiratory phase, and sniffing flow patterns of the olfactory area. DESIGN An anatomically correct 3-dimensional nasal and pharyngeal cavity was constructed from computed tomographic images of a healthy adult nose and pharynx. The unsteady state Navier-Stokes and continuity equations were solved numerically on inspiratory and expiratory nasal flow and sniffing. SETTING Numerical simulation application. MAIN OUTCOME MEASURES The detailed velocity distribution and streamline distribution of nasal airflow were visualized using the computational fluid dynamics method (an imaging technology for regional flow factors [velocity and streamline]). RESULTS The inspiratory flow passes through a wider olfactory area than the expiratory flow, and the sniffing flow passes through the widest olfactory area without increasing the velocity of the airflow. In addition, a recirculating flow strongly promotes olfactory function. CONCLUSION The computational fluid dynamics model allows for the investigation of the flow mechanisms in the human olfactory groove.

Impaired Air Conditioning within the Nasal Cavity in Flat-Faced Homo.

We are flat-faced hominins with an external nose that protrudes from the face. This feature was derived in the genus Homo, along with facial flattening and reorientation to form a high nasal cavity. The nasal passage conditions the inhaled air in terms of temperature and humidity to match the conditions required in the lung, and its anatomical variation is believed to be evolutionarily sensitive to the ambient atmospheric conditions of a given habitat. In this study, we used computational fluid dynamics (CFD) with three-dimensional topology models of the nasal passage under the same simulation conditions, to investigate air-conditioning performance in humans, chimpanzees, and macaques. The CFD simulation showed a horizontal straight flow of inhaled air in chimpanzees and macaques, contrasting with the upward and curved flow in humans. The inhaled air is conditioned poorly in humans compared with nonhuman primates. Virtual modifications to the human external nose topology, in which the nasal vestibule and valve are modified to resemble those of chimpanzees, change the airflow to be horizontal, but have little influence on the air-conditioning performance in humans. These findings suggest that morphological variation of the nasal passage topology was only weakly sensitive to the ambient atmosphere conditions; rather, the high nasal cavity in humans was formed simply by evolutionary facial reorganization in the divergence of Homo from the other hominin lineages, impairing the air-conditioning performance. Even though the inhaled air is not adjusted well within the nasal cavity in humans, it can be fully conditioned subsequently in the pharyngeal cavity, which is lengthened in the flat-faced Homo. Thus, the air-conditioning faculty in the nasal passages was probably impaired in early Homo members, although they have survived successfully under the fluctuating climate of the Plio-Pleistocene, and then they moved “Out of Africa” to explore the more severe climates of Eurasia.

Examination of Extraction with Vortex Regions in Paranasal Sinus of Human Nose

The nasal cavity has functions which is breathing, smelling, humidification, warming and cleaning of the inhaled air. It is important for human life-sustaining. And nasal cavity has complex anatomy. In this paper, we have examined the flow/vortex in paranasal sinus. Paranasal sinus divides into four parts depend on location, 1) Maxillary Sinuses, 2) Frontal Sinuses, 3) Ethmoidal Sinuses and 4) Spenoid Sinuses. We focus especially Maxillary Sinuses (MS) in this paper. Maxillary Sinuses is an area connected with both sides of both nasal cavities one by one. The examination of the simulation of the nasal cavity that contains the MS is not enough. And, we thought that MS has some influences for flow of nasal cavity. Therefore, we examine flow in nasal cavity that contains MS. In the general, CFD (Computational Fluid Dynamics) simulation results are visualized by general visualization method such as Vector, Stream lines, Particle flow and LIC (Line Integral Convolution). By these techniques, the flow can be abstractly understood. However, the vortex area cannot be clearly visualized. Especially, shape of vortex region is necessary to understand the phenomenon in MS and connected point between nasal cavity and MS. In this paper, we have examined extraction method for airflow as cavity flow. There are some extraction methods of vortex regions, for example, Lambda2, Q-criterion and vorticity magnitude, etc [3]. And we have extracted vortex regions from results of simulation in nasal cavity. In the result, we can see the two vortexes in MS, and we confirmed it was right and left of MS and the result was different. The shape of MS is right and left and slightly different. However, the pattern of the flow became a different clearly.

Examination of Heating and Cooling Function in Nasal Cavity That Applies Heat Conduction Model to Inner Wall

Heating is a main function of a nose. The most important contribution to this function is made by the upper respiratory tract before the air reaches the laryngotracheal region [1]. The examination of the temperature distribution in the nasal cavity by the measurement and numerical analysis was done in previous research [1–3]. However, accurate measurement of the temperature distribution in nasal cavity is technically difficult, and there isn’t the research of numerical simulation about the distribution of the temperature on the wall including the inflow temperature influence. In this study, we set the temperature condition in inner wall, and we used the heat conduction model to inner wall. The heat source is a blood that surrounds the nasal cavity. It exists in the nasal cavity wall. The temperature distribution inside the nasal cavity or on the surface of the boundary wall was examined. Moreover, the nasal cavity shape was restructured with the medical CT images of the volunteer. So far, we have examined the flow in the nasal cavity according to the nasal cavity shape restructured with the CT images [4]. In result, we showed that air was heated enough by the temperature of wall and the result by the heat conduction model showed a good agreement with the measurement result of the research of Keck [1]. In addition, because flow velocity was different with the right and left nasal cavity, the temperature distribution of a right and left nasal cavity was different. Moreover, the flow profile and the temperature distribution depended on each volunteer’s shape and were different.Copyright