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.     

Intraoral pressure, nasal pressure and airflow rate in cleft palate speech

We have suggested that compensatory behaviors associated with cleft palate may be strategies developed for the purpose of satisfying the requirements of a speech regulating system. The purpose of the present study was to test this hypothesis in subjects demonstrating various degrees of velopharyngeal inadequancy. The pressure-flow technique was used to assess aerodynamic responses to a loss of velar resistance in 74 subjects compared to a control group of 137 subjects with adequate velopharyngeal closure. The results of this study demonstrate that as degree of inadequacy increased, airflow rate also increased. Although intraoral pressure fell as inadequacy increased, many subjects were able to maintain pressures above 3.0 cm H2O by increasing airflow rate. Nasal pressure increased in proportion to the decrease in intraoral pressure while combined nasal plus oral pressure remained constant across groups. These findings suggest that a loss of resistance at the velar port is compensated by an increase in resistance at the nasal port. Airflow rate appears to be adjusted to total upper airway resistance. These findings support our contention that the speech system is constrained to meet aerodynamic requirements.     

The relationship between nasalance and nasal resistance to airflow.

The relationship between nasal airway resistance and nasalance in healthy volunteers and in subjects suffering from symptoms of acute rhinitis was investigated. A non-invasive objective measure of nasalance using the Nasometer (Kay Electronics) was used and an inverse correlation between airway resistance and nasalance was found (r = 0.67, r2 = 0.46, p less than 0.0001). The effect of a topical nasal decongestant on nasal airway resistance and nasalance was investigated, and significant changes were seen both in resistance and nasalance (p less than 0.0001) with a correlation in the changes seen in both parameters (r = 0.82, r2 = 0.66, p less than 0.0001). The measure of nasalance may be useful in assessing various forms of nasal treatment including nasal, adenoidal and palatal surgery. The measurement of nasalance is well tolerated by subjects of all ages and is particularly useful in subjects with high nasal resistance where rhinomanometry tends to be unstable.     

The nasal airflow in noses with septal perforation: a model study

BACKGROUND: Septal perforation is a common clinical problem in rhinology. Affected patients suffer from a dry nose, crusts as well as recurrent epistaxis and sometimes an inspiratory whistle. The aim of this study was to investigate the underlying flow dynamic mechanisms. METHODS: The physical flow effects of such pathologies were examined in functional nose models (box models) and anatomically exact models of the nose. Therefore, septal perforations of different sizes and localisations were studied in straight and deviated nasal septa. RESULTS AND CONCLUSIONS: It could be seen that the localisation of the perforation has no impact on the flow pattern. In large septal perforations, the air jet collides with the posterior edge of the perforation and disintegrates turbulently. Since airflow is physiologically turbulent in the posterior part of the nose, posterior perforations do not cause clinical complaints. The inspiratory whistling sound during respiration is based on the principle of a lip whistle. Large perforations do not cause a whistling sound. The necessary high flow velocity needed in large perforations is usually not achievable.     

Biophysics of nasal airflow: a review

An account is given of the constituents of the flow resistive nasal valve, their aerodynamic function, and the essential role they play in processing inspiratory air. The relatively fixed structural component and the variable mucovascular components of the lateral and medial nasal walls are described, and particular attention is drawn to the septal mucovascular component because its existence is not universally recognized. Common sources of error in subjective and objective assessments of obstruction to nasal respiratory airflow are discussed. Comments are presented advocating limitations of surgical interference in the treatment of mucosal and structural nasal airway obstruction.     

Resistance to respiratory airflow of the nasal passages: comparisons between different common methods of calculation

Computer assisted active posterior rhinomanometric determinations of resistance were made with four adult subjects. A face mask and pneumotach were used to measure respiratory airflow. The magnitude and variation of six different instantaneous and time averaged methods of calculation of resistance resulting from simultaneous measurements were compared. Over a resistance range of 1-6 cm H2O/l/sec (0.1-0.6 Pa/cm3/sec) time averaged results approximated those computed at 75 Pa and were 20-25% less than those at 150 Pa. Over the same range of nasal patencies, the coefficients of variation averaged 6-8% in 144 series of 10 measurements which were obtained from six modes of resistance computation in four subjects (total 1440). Time averaged results showed the least variation. A frequency range of 10-26 breaths/min increased the coefficient of variation only to 9% and a ventilation range of 7-24 l/min increased it to 11%, quantitative relationships between resistances and pattern of breathing were not evident. Mask positioning was critical, small maladjustments resulted in large resistive changes.     

Role of nasal valve in the surgically corrected nasal respiratory obstruction: evaluation through rhinomanometry.

The aim of this study was to evaluate the improvement of nasal flow and the fall of nasal resistance in 50 patients that underwent rhinoseptoplasty in our department and discuss the relative importance of valvular and septal deformities in nasal airway obstruction. Fifty consecutive patients underwent rhinoseptoplasty to improve nasal obstruction caused by severe septal deviation, external or internal valvular incompetence, or any combination of the three. We excluded patients with minor septal curvatures, septal perforations, or turbinate hypertrophy. Preoperative and postoperative rhinomanometry was performed on all 50 patients. In all 50 patients, septal and/or valvular surgery lowered nasal resistance in 90% of cases. Septoplasty alone with medial and basal osteotomies did not improve nasal flow (p < 0.4), whereas the correction of valvular obstruction alone increased nasal airflow in a statistically significant way (p < 0.0001). Moreover, patients with both valvular incompetence and septal deviation represented the group in which the greatest preoperative obstruction and the greatest postoperative improvement occurred. Nasal valvular function should be assessed with rhinomanometry in all preoperative rhinoplasty patients with airway obstruction. In many cases, valvular effects may surpass septal deviation as the primary cause of nasal airflow obstruction.     

Reciprocal changes in nasal resistance to airflow caused by pressure applied to the axilla

The resistance to airflow of each nasal passage was measured using active, posterior, rhinomanometry. Application of pressure to the axilla for 15 min by means of a wooden crutch caused a reciprocal change in nasal resistance with an ipsilateral increase and a contralateral decrease in resistance. The results are discussed in terms of reflex changes in sympathetic tone to the nasal venous erectile tissue.     

Human respiratory cells from nasal polyps as a model for gene transfer by non-viral cationic vectors

The influence of cell differentiation and proliferation on cationic vector mediated gene transfer into the explant-outgrowth cell culture from nasal polyps was investigated. Respiratory cells were categorized into two groups based on the expression of cytokeratin filaments (CKs), which were used as differentiation markers. Outgrowths grown for 2 weeks expressed similar levels of CKs 14, 13 and 18 showing a de-differentiated phenotype, while outgrowths cultured for 4 weeks presented very high levels of CK 13, high CK 14 and low CK 18 expression and were squamous differentiated. De-differentiated cells presented higher proliferation indexes than squamous cells. Gene transfer levels, as evaluated using a quantitative reporter gene (firefly luciferase), were significantly higher in the 2- than in the 4-week-old outgrowths. Cationic vector transfected respiratory cells were located both proximally and distally to the explant, as shown by enzymatic staining of beta-galactosidase-positive cells. Respiratory cell outgrowths from nasal polyps can be considered a suitable model to study gene transfer protocols in vitro.     

A comparison of the effects of two commonly used vasoconstrictors on nasal mucosal blood flow and nasal airflow.

This study compared two commonly used vasoconstrictors, cocaine and xylometazoline. Non-invasive techniques of measurement were utilised, with active anterior rhinomanometry indirectly assessing changes in nasal mucosal blood volume, and laser Doppler flowmetry assessing changes in nasal mucosal blood flow. Twelve healthy volunteers received 0.1 ml of the topical vasoconstrictor at the anterior end of both inferior turbinates. Following the application of xylometazoline, a significant rise in nasal airflow (p less than 0.005), and a significant fall in blood flux occurred in the probe nostril (p less than 0.05). Following the application of cocaine, no significant change in nasal airflow occurred (p less than 0.05), but a significant fall in blood flux occurred in the probe nostril (p less than 0.02). A comparison of the paired data for the same subject demonstrated no significant difference in the change in blood flux produced by xylometazoline and cocaine, but a significant difference in the change in airflow produced by the two vasoconstrictors (p less than 0.005).     

A dynamic and direct visualization model for the study of nasal airflow.

OBJECTIVE: To evaluate nasal airflow characteristics during physiologic breathing in normal and pathologic conditions. DESIGN: The choana of an anatomical human model was connected to a pump that simulated physiological pressure changes in the upper airway system. Normal ambient air was used as medium. The airstream was marked with aerosolized water particles, and was observed through an exact but translucent replica of the original nasal septum. RESULTS: In physiologic conditions the airflow is mixed. Turbulence is clearly visible even with low flow velocities. There is less turbulence with lower flow rates. The nasal airflow follows a triphasic pattern of acceleration, near-steady state, and deceleration. Turbulence is prominent in the first and third phases. The main flow stream passes through the middle meatus at all rates. Hypertrophic mucosal membranes and turbinates increase the proportion of air passing the middle meatus. With decongested turbinates, flow distribution is more even. After turbinectomy there is a significant amount of airflow passing along the floor of the nose. The olfactory region is aerated only toward the end of inspiration and during the entire expiration phase. CONCLUSIONS: This model allows the investigation of airflow distribution and turbulence under physiologic conditions and the examination of the influence of pathologic conditions on these parameters. Overzealous trimming of turbinates results in an unphysiologic distribution of airflow.     

Nose/mouth distribution of respiratory airflow in 'mouth breathing' children

Oro-nasal distribution of respiratory airflow was determined in 120 'mouth breathing' children by a minimally invasive computer-assisted method that employed a modified CPAP nasal mask/pneumotach and a head-out body plethysmograph. Resulting measurements were reproducible but clinical assessments correlated poorly with these values. Airflow distribution was almost identical in inspiration and expiration. 100% nasal breathing was found over a wide range of nasal resistances, many subjects with lips apart. Overall, the nasal fraction was negatively correlated with resistance and it was increased by topical decongestant. Decreasing nasal resistance with increasing age was confirmed, but corresponding changes in airflow distribution were not demonstrated. Quantitative assessment is advocated in clinical management of 'mouth breathers'.     

The relationship between middle ear pressure and deviated nasal septum

The deviated nasal septum may be associated with middle ear problems, particularly on the side of nasal obstruction. This study aims to find out whether middle ear pressure (MEP) correlates with the degree of nasal obstruction secondary to a deviated nasal septum, and to examine changes in MEP following septal surgery. Patencies of the nasal passages (measured with a peak nasal inspiratory flowmeter) and MEP (measured with tympanometer) of 55 patients were obtained prior to surgery and 7.5 (6–10) months post-operatively [median (range)]. Forty patients completed the study. Results were analysed by linear regression. In the ear on the side of nasal blockage, MEP was -25.7±28.4 mm water pre-operatively, and following surgery increased significantly to -2.9±30.4 mm water (mean±sd ) (P < 0.001). Pre-operatively, it was inversely related to the difference in patencies between the two nasal passages (r = -0.32, P < 0.02). Post-operatively, its improvement correlated with the degree of reduction of asymmetry of airway patency (r = 0.56, P < 0.001).     

鼻腔气道三维重建和气流流场的数值模拟与分析

目的:探讨鼻腔气流流场与鼻腔气道结构、功能之间的关系。方法:根据CT对25例健康中国人鼻腔气道进行表面三维重建和有限元剖分,设定边界条件后求解Navier-Stokes方程,分析通气量为10L/min时吸气相的气流流场。结果:①5例以双侧鼻腔通气为主,气流主要流经总鼻道中部;20例以一侧鼻腔通气为主:在主要通气侧气流主要经过总鼻道中、下部,在非主要通气侧气流主要经过总鼻道中部。②气流速度在鼻阈,总鼻道中部、下部主要通气侧和非主要通气侧均差异具有统计学意义,在嗅裂,中、下鼻道双均侧差异无统计学意义;③主要通气侧流速在鼻阈最快,在总鼻道中部、下部次之,在中、下鼻道,嗅裂最慢;非主要通气侧气道各部位流速均差异无统计学意义。结论:①10L/min时总鼻道中、下部起主要通气作用。②鼻阈、下鼻甲、中鼻甲依次对进入鼻腔的气流进行有效、合理分流,鼻周期可能与之相关。     

Peak Nasal Inspiratory Flow Evaluation as an objective method of measuring nasal airflow

Acoustic rhinometry, rhinomanometry and Inspiratory Peak Nasal Flow (IPNF) are used in order to objectively assess nasal patency. These are expensive not very practical tests, except for IPNF, which is a fast, simple and low cost method.ObjectiveTo assess IPNF in healthy individuals complaining of nose obstruction caused by allergic rhinitis.MethodIPNF use in 78 individuals with and without rhinitis symptoms.Study designContemporary cross-sectional cohort.ResultsIPNF showed significant results for nasal obstruction, rhinorrhea, pruritus, sneezes and tearing (p < 0.001). There was no correlation between the presence of nasal septum deviation and IPNF (p = 0.561). We found a positive correlation between IPNF and the Visual Analogue Scale (VAS) for nasal obstruction (p = 0.002). In the multiple linear regression model, there was a statistical significance between the values found in IPNF with allergic rhinitis and age (p = 0.005 and p = 0.023 respectively).ConclusionIPNF proved to be a reliable method to detect changes in nasal patency, by obstructive causes as well as inflammatory causes, with an acceptable level of statistical significance, simple, easy to handle, inexpensive and reproducible.