The influence of nasal flow aerodynamics on the nasal physiology

The ability of the human nose to warm and humidify the respiratory air is important to maintaining the internal environment of the lungs, since ambient air is conditioned to nearly alveolar conditions (body temperature and fully saturated with water vapour) upon reaching the nasopharynx. Because of very short time of the inspiratory phase duration, as well as expiratory phase, only the rich vascularization of the nasal mucosa and specific organization of the submucosal vessels are not able to assure such effective physiological activity. Therefore the type of airflow during the respiration is essential to understanding the functional possibilities of the nasal mucosa. Most studies have investigated the airflow only in steady-flow conditions, where the laminar flow was observed. Anatomically accurate physical models of real nasal cavities and particle image velocimetry allow evaluation of the entire flow field in the nasal cavity. In these investigations a partially turbulent flow was observed even at low air velocities in most part of the nasal cavity. From a physiological perspective, a turbulent flow would seem sensible, since it enhances contact between air and the mucosal layer. By doing so, the nasal physiological functions - humidification, cleaning and warming are optimized.     

Investigations of the influence of external nose deformities on nasal airflow

BACKGROUND: Abnormalities of the external shape of the nose are often felt as cosmetically disturbing. In many cases an additional hampering of the respiratory function of the nose is seen and causes pathological nasal airflow patterns. For the functional outcome of aesthetic-surgery of the nose, knowledge of nasal flow is essential. In the medical literature there are some discrepancies between the relationship of nasal shape and nasal flow. We investigated typical airflow patterns in different abnormalities of the external nose. METHODS: We performed fluid dynamic experiments on exact, anatomical nasal models and functional nasal models (so-called modified Mink boxes). We investigated the inspiratory flow pattern in nose-models with typical variations of the shape of the external nose. RESULTS AND CONCLUSIONS: There were typical airflow patterns for every external nasal abnormalities. The normal nose shows a disturbance of the streamlines over the entire nasal cavum. Under physiological flow velocities we find laminar and turbulent flow. The pathological variations of the nasal shape show mostly different airflow patterns and characteristics. The main reason for that is a deformed or anatomically false configurated inflow area (vestibulum, isthmus and anterior cavum). During rhinoplasty the reconstruction of the nasal inflow area has to be taken into account.     

鼻中隔偏曲者鼻腔结构自适应改变的特征分析

目的 对10例鼻中隔偏曲者及20例健康北方人的鼻腔结构进行三维重建,将二者气流流场进行数值模拟,分析二者鼻腔气道气流流场特征,探讨其与鼻腔结构和功能之间的关系.方法 根据10例鼻中隔偏曲者和20例健康人的鼻腔CT影像,应用表面重建的方法对鼻腔气道进行三维重建,用有限元法对气流进行数值模拟,分析二者鼻腔气道气流流场特征.结果 从模拟的速度云图得出鼻中隔偏曲者通过双侧鼻腔的气流量以气道宽敞侧鼻腔为主,以总鼻道中部最为明显.健康人鼻腔气流量以一侧鼻腔为主,以总鼻道中部、总鼻道下部为明显.从模拟的压强云图得出鼻中隔偏曲者在鼻中隔偏曲最为明显处气压下降最快,占气道总压强差值的71.36%;健康人于鼻阈处气压下降最快,占气道总压强差值的58.78%.鼻中隔偏曲者鼻腔气道阻力较健康人增大.结论 数字化三维重建鼻腔气道模型可反映鼻腔气流通道的基本特征,可用于分析因鼻腔解剖结构异常而导致的鼻腔空气动力学特征改变,本实验初步证明鼻腔结构自适应功能的存在,为鼻腔自适应模型的建立打下基础.     

The nasal cycle in respiratory defence

The review describes the phenomenon of the nasal cycle, which consists of periodic congestion and decongestion of the nasal venous sinuses and an alternation of airflow from one side of the nose to the other over a period of several hours. The hypothesis is put forward that the nasal cycle may have a role in respiratory defence by; (a) alternation of the work of air conditioning between the nasal passages (b) generation of a plasma exudate which physically cleanses the epithelium and provides a source of antibodies and inflammatory mediators (c) maintaining the patency of the airway during the inflammatory response to infection.     

Numerical simulation of normal nasal cavity airflow in Chinese adult: a computational flow dynamics model

Our purpose is to simulate the airflow inside the healthy Chinese nose with normal nasal structure and function by computational fluid dynamics (CFD) method and to analyze the relationship between the airflow and physiological function. In this study, we used the software MIMICS 13.0 to construct 20 3-dimensional (3-D) models based on the computer tomography scans of Chinese adults’ nose with normal nasal structure and function. Thereafter, numerical simulations were carried out using the software FLUENT 6.3. Then the characteristics of airflow inside the airway and sinuses were demonstrated qualitatively and quantitatively in steady state. We found that during the inhalation phase, the vortices and turbulences were located at anterior part and bottom of the nasal cavity. But there is no vortex in the whole nasal cavity during the expiratory phase. The distributions of pressure and wall shear stress are different in two phases. The maximum airflow velocity occurs around the plane of palatine velum during both inspiratory and expiratory phases. After the airflow passed the nasal valve, the peak velocity of inhaled airflow decreases and it increases again at the postnaris. Vice versa, the exhaled airflow decelerates after it passed the postnaris and it accelerates again at nasal valve. The data collected in this presentation validates the effectiveness of CFD simulation in the study of airflow in the nasal cavity. Nasal airflow is closely related to the structure and physiological functions of the nasal cavity. CFD may thus also be used to study nasal airflow changes resulting from abnormal nasal structure and nasal diseases.     

The role of the temperature of the nasal lining in the sensation of nasal patency

The receptors and neural pathways involved in the common symptom of nasal blockage are of great interest. Studies to date suggest that the sensation of nasal patency may be related to the temperature of the nasal passages. Sixty-two subjects were asked to assess their own nasal patency subjectively and indicate this on a visual analogue scale. The temperature of the nasal lining was continuously recorded during quiet nasal repiration using a non-contact infrared themometer. The cooler the nasal lining, the clearer the nose felt, and the greater the drop in temperature on inspiration again the clearer the nose felt. The study supports the previously proposed hypothesis that the sensation of nasal airflow is derived from a cooling of the nasal lining on inspiration, and this is probably detected by cold thermoreceptors in the mucosa.     

Effects of size of the nasal airway on nasal airflow rate

The controversy concerning the effects of nasal airway impairment on facial growth has stimulated renewed interest in upper airway respiratory function. We assessed the relationship between nasal airway patency and nasal airflow rate, using the pressure-flow technique to estimate nasal cross-sectional size and nasal airflow rate in 30 normal and 82 nasally impaired adults. Groups were categorized according to otolaryngologic examination results and pressure-flow measurements. The results clearly demonstrate that size of the airway influences airflow rate when the smallest nasal cross-sectional area is under 0.4 cm2. The data suggest that the nose becomes flow-limiting when it is less than 0.18 cm2. These data support our contention that nasal airway impairment in adults occurs when the airway is less than 0.4 cm2 in size.     

Olfactory ability as a function of nasal air flow volume in laryngectomees

This study tested a number of hypotheses concerning the interrelationships between the olfactory abilities and the volume of nasal airflow in laryngectomees. Data were collected from 25 laryngectomees and 25 control subjects and comprised the following: 1) Odor threshold and identification test results. In the threshold test, an 11-step aqueous dilution series of butanol was used. In the odor identification tests, 14 common odorants were used. 2) Measurement of nasal air flow volume in liters per minute. For olfaction and airflow, the laryngectomees' measurements were made under two conditions: 1) using unassisted airflow through the nose, and 2) using a laryngeal bypass that linked the stoma to the mouth and allowed airflow through the nose. The major findings showed that among laryngectomees olfactory abilities depend on nasal airflow. It is concluded that laryngectomees have intact olfactory mechanisms that function normally when adequate airflow volume is provided.     

The choana and nasal obstruction

A subject with a septal perforation was studied rhinometrically to confirm that the congested choana did not limit airflow when the anterior nose was decongested. It did not. This suggests that in an undefined proportion of patients with swollen diseased mucosa, surgery to the anterior nose may be sufficient to relieve nasal obstruction.     

Investigating the nasal cycle using endoscopy,rhinoresistometry, and acoustic rhinometry

OBJECTIVES: Cyclic congestion and decongestion in the two nasal cavities is seen in connection with the respiratory function of the nose. The turbulent behavior of nasal airflow is a prerequisite for adequate contact of inspired air particles with the mucosa. The aim of this study was to gain insight into this turbulent behavior of nasal airflow during the nasal cycle. METHODS: The nasal cycle in 10 healthy human subjects was investigated using endoscopic imaging, rhinoresistometry, and acoustic rhinometry every 20 minutes over a time period of up to 15 hours. The following parameters were recorded for each nasal cavity: airflow resistance, hydraulic diameter, friction coefficient lambda as an indicator for the wall configuration triggering turbulence, transition from laminar to turbulent flow, and the minimal cross-sectional areas. RESULTS: In addition to the known cyclic change of flow resistance and nasal width, a periodic change in the turbulence behavior was observed. In the resting phase, mainly laminar flow was found. During the working phase, the onset of turbulence occurred already at low flow velocities. The increase of turbulence during the working phase is caused by the increase in cross-sectional area in the anterior cavum due to decongestion of the mucosa of the head of the inferior turbinate and the septal tuberculum. CONCLUSIONS: Rhinoresistometry and acoustic rhinometry complement each other. The combination of the two methods provides insight into the functional changes during the nasal cycle and into nasal physiology in general. The authors therefore advocate a combination of the two methods for functional evaluation of the nasal airway.     

Hemophilus influenzae adherence to and absorption from the nasal mucosa of guinea pigs

The adherence to and the absorption from nasal mucosal epithelium of type b and non-typeable strains of Hemophilus influenzae were studied in guinea pigs. H. influenzae bacteria were administered to the nose as 4 x 10(7) organisms in 1.0 ml saline. The outer membrane vesicles (OMV) of H. influenzae were used in the absorption study. Scanning electron microscopic studies showed that H. influenzae cells attached to both ciliated and non-ciliated cells of the nasal mucosa. Histological studies showed that OMV were absorbed through the nasal mucosa, mainly from ciliated cells. Further, penetration of OMV through the nasal mucosa of immunized animals was reduced when compared with that of non-immunized ones.     

The effect of L-menthol stimulation of the major palatine nerve on nasal patency.

Objective and subjective measurements of nasal patency were made before and after L-menthol stimulation of the palatal mucosa (supplied with the trigeminal nerve) in 15 normal adult subjects. The stimulation exerted indirect effect on the nasal cavity in that all subjects mentioned a cold sensation in their nose and a sensation of increased nasal patency, but no influence on nasal resistance to airflow was detected.     

The site and function of the nasal valve

Previous observers have suggested that the main site of respiratory airflow resistance is localized to the vestibular region of the nose. This resistive segment of the airway was investigated using a “head-out” body plethysmograph in subjects with anatomically normal noses (a) untreated, (b) congested and (c) decongested. In all three conditions, 2/3 of the total nasal airflow resistance was found within the bony cavum in the vicinity of the pyriform aperture and about 1/3, in the cartilaginous vestibule. As might be expected, caval resistance changed proportionately with the degree of mucosal congestion; but, more surprisingly, vestibular resistance changed similarly. This was due in part to the observed forward expansion of the anterior ends of the inferior turbinates with congestion. EMG recordings in subjects breathing through both nostrils demonstrated a gradation of inspiratory alar dilator muscle activity with increased minute ventilation and with mucosal congestion, and there was no evidence of inspiratory alar collapse. But with elevated ventilation through one nostril only, or when the alar muscles were paralyzed by lidocaine block of the VIIth nerve, alar collapse occurred. These findings are of importance in the management of the congested but anatomically normal nose and in surgery of the nasal tip.     

The effects of camphor, eucalyptus and menthol vapour on nasal resistance to airflow and nasal sensation

The effects of five minutes exposure to camphor, eucalyptus or menthol vapour on nasal resistance to airflow and nasal sensation of airflow were compared with the effects of exercise on the nose. Inhalation of camphor, eucalyptus or menthol had no effect on nasal resistance to airflow but the majority of subjects reported a cold sensation in the nose with the sensation of improved airflow. Exercise caused a decrease in nasal resistance but did not induce any nasal sensation of cold or improved airflow. The results indicate that camphor, eucalyptus and menthol stimulate cold receptors in the nose. The clinical significance of nasal sensation of airflow is discussed.     

Diagnosis and treatment of congenital defects and abnormalities of the nasal cavity in children and adults

In 300 patients with congenital defects and abnormalities of the nasal cavity development, physiological functions of the nose were investigated, using advanced methods, e. g. rhinofibroscopy, microrhinoscopy, rhinopneumometry, olfactometry, thermometry of the nasal mucosa, and pH measurement of the nasal mucus. Disorders in respiratory, olfactory, and protective functions were revealed. This led to surgical intervention in more than 300 cases. Original methods and modified procedures were developed as applied to specific pathologies. Physiological measurements before and after surgery demonstrated that correction of development defects and abnormalities of the nasal cavity contributed to the recovery of nose functions.     

Scanning and transmission electron microscopic aspects of the nasal acilia syndrome

A 3-month-old boy was admitted with failure to thrive and persistent fevers. During a 4 month hospitalization for treatment of suspected sepsis, persistent purulent nasal discharge developed. Biopsies of his nasal mucosa on 3 separate occasions disclosed thinned respiratory epithelium and a complete absence of cilia when examined by electron microscopy (EM). Despite an initial granulocytopenia and a wide range in T-cell numbers, he did not show any evidence of lower respiratory tract infection. A tracheal biopsy processed for EM demonstrated normal ciliated epithelium. This patient appears to have an unrecognized syndrome of normal tracheal cilia but absent nasal cilia.     

Histological investigations of the nasal mucosa in human fetuses

The adult nasal mucosa has been exposed to various external agents and selected physiological conditions. Changes in intranasal airflow influenced the morphological appearance of the mucosa. Studies of agents on the fetal mucosa and its development may contribute to better understanding of the morphology of the nasal mucosa. The authors studied the nasal mucosa of 20- to 26-week-old fetuses using light microscopy and scanning and transmission electron microscopy. Findings showed that this developing nasal mucosa took part in the production and movement of mucus in the nasal cavity.     

Improvement of the nasal airflow by the nasal dilator Nozovent

The lateral wall of the nostril is considered as the functional unit in the regulation of the nasal resistance causing more than half of the total resistance. In 16 test-subjects both nostrils were dilated with a plastic nasal device, Nozovent, and the airflow through the nose was measured with and without the device. In each object the mean value of ten inspirations at 150 Pa was calculated. Before the application the mean value of the subjects was 0.68 l/sec and with the device 0.84 l/sec. The improvement of airflow was comparable with that of treatment with nose-drops. The device ought to be helpful in patients with or without collapsing ala nasi during the night to increase nasal airflow when sleeping.     

Clinical and cytomorphological alterations of nasal mucosa in laryngectomized patients

A group of laryngectomized patients were rhinoscopically examined. The nasal mucosa was found to become thinner and change its colour over time. The nasal mucosa swabs from the same patients were cytologically examined at various time intervals following laryngectomy, revealing degenerative alterations of the multi-layered epithelium that occurred as a consequence of the nose exclusion from its function due to laryngectomy. Our experience has shown these degenerative changes to be completed within a two-year post operative period, as indicated by the fact that both the clinical and cytological findings obtained after that time point remained practically unchanged.