Airway Airflow Research Articles

Inhaled silica-coated TiO2 nanoparticles induced airway irritation, airflow limitation and inflammation in mice

The wide use of nanotechnology is here to stay. However, the knowledge on the health effects of different engineered nanomaterials (ENMs) is lacking. In this study, irritation and inflammation potential of commercially available silica-coated TiO2 ENMs (10 × 40 nm, rutile) were studied. Single exposure (30 min) at mass concentrations 5, 10, 20 and 30 mg/m3, and repeated exposure (altogether 16 h, 1 h/day, 4 days/week for 4 weeks) at mass concentration of 30 mg/m3 to silica-coated TiO2 induced first phase of pulmonary irritation (P1), which was seen as rapid, shallow breathing. During repeated exposures, P1 effect was partly evolved into more intense pulmonary irritation. Also sensory irritation was observed at the beginning of both single and repeated exposure periods, and the effect intensified during repeated exposures. Airflow limitation started to develop during repeated exposures. Repeated exposure to silica-coated TiO2 ENMs induced also pulmonary inflammation: inflammatory cells infiltrated in peribronchial and perivascular areas of the lungs, neutrophils were found in BAL fluids, and the number of CD3 and CD4 positive T cells increased significantly. In line with these results, pulmonary mRNA expression of chemokines CXCL1, CXCL5 and CXCL9 was enhanced. Also expression of mRNA levels of proinflammatory cytokines TNF-α and IL-6 was elevated after repeated exposures. Taken together, these results indicated that silica-coated TiO2 ENMs induce pulmonary and sensory irritation after single and repeated exposure, and airflow limitation and pulmonary inflammation after repeated exposure.

A COMPARATIVE OF ANALYTICAL AND NUMERICAL SIMULATIONS FOR THE OSCILLATING AIRFLOW IN A HUMAN ORAL AIRWAY

Understanding and more accurate simulation of the oscillation airflow are important to aerosolized therapy. To assure the power of simulation by analytical method, in this paper, we present an effective computational method of finite element analysis to compared with the results obtained by an analytical expression in a Fourier series-based form which is presented by S. Kongnuan and J. Pholuang in their previous work. The finite element analysis is implemented by using the commercial software, COMSOL Multiphysics 3.5a. The airflow fields at different times of each breathing period by both methods are simulated and then compared. The comparative of the results from both methods show a good agreement and agree to the fact of the airflow in a human airway and other related publications. AMS Subject Classification: 65M60, 76D05, 92B05, 97M60

Simulation analysis of airflow alteration in the trachea following the vascular ring surgery based on CT images using the computational fluid dynamics method

This study presents a computational fluid dynamics (CFD) model to simulate the three-dimensional airflow in the trachea before and after the vascular ring surgery (VRS). The simulation was based on CT-scan images of the patients with the vascular ring diseases. The surface geometry of the tracheal airway was reconstructed using triangular mesh by the Amira software package. The unstructured tetrahedral volume meshes were generated by the ANSYS ICEM CFD software package. The airflow in the tracheal airway was solved by the ESI CFD-ACE+ software package. Numerical simulation shows that the pressure drops across the tracheal stenosis before and after the surgery were 0.1789 and 0.0967 Pa, respectively, with the inspiratory inlet velocity 0.1 m/s. Meanwhile, the improvement percentage by the surgery was 45.95%. In the expiratory phase, by contrast, the improvement percentage was 40.65%. When the inspiratory velocity reached 1 m/s, the pressure drop became 4.988~Pa and the improvement percentage was 43.32%. Simulation results further show that after treatment the pressure drop in the tracheal airway was significantly decreased, especially for low inspiratory and expiratory velocities. The CFD method can be applied to quantify the airway pressure alteration and to evaluate the treatment outcome of the vascular ring surgery under different respiratory velocities.

On locating the obstruction in the upper airway via numerical simulation

The fluid dynamical properties of the air flow in the upper airway (UA) are not fully understood at present due to the three-dimensional (3D) patient-specific complex geometry of the airway, flow transition from laminar to turbulent and flow-structure interaction during the breathing cycle. It is quite difficult at present to experimentally measure the instantaneous velocity and pressure at specific points in the human airway. On the other hand, direct numerical simulation (DNS) can predict all the flow properties and resolve all its relevant length- and time-scales. We developed a DNS solver with the state-of-the-art lattice Boltzmann method (LBM), and used it to investigate the flow in two patient-specific UAs reconstructed from CT scan data. Inspiration and expiration flows through these two airways are studied. The time-averaged first spatial derivative of pressure (pressure gradient), ∂p/∂z, is used to locate the region of the UA obstruction. But the time-averaged second spatial derivative, ∂2p/∂z2, is used to pinpoint the exact location of the obstruction. The present results show that the DNS-LBM solver can be used to obtain accurate flow details in the UA and is a powerful tool to locate its obstruction.

Obstructive sleep apnoea in children: perioperative considerations

Obstructive sleep apnoea (OSA) has become a major public health concern as its incidence and severity have increased in tandem with the obesity epidemic. In children, OSA is now recognized as a common disorder and can be associated with significant morbidity. OSA belongs to a spectrum of diagnoses known as sleep-related breathing disorders in which the airway is completely (apnoea) or partially (hypopnoea) occluded during sleep despite continued respiratory efforts. This airway obstruction can cause abnormal gas exchange leading to hypoxaemia, hypercapnia, sleep fragmentation, and their attendant physiological and behavioural consequences. The degrees of hypercapnia, hypoxaemia, and upper airway airflow reduction are the primary factors determining the severity of OSA. In young children, adenotonsillar hypertrophy is the most common anatomical abnormality associated with OSA, and adenotonsillectomy is, therefore, the most common surgical intervention. Perioperative complications associated with adenotonsillectomy are more common in children with severe OSA. A thorough understanding of the pathophysiology of OSA, careful and complete preoperative assessment, meticulous intraoperative and postoperative management, and early recognition of potential perioperative complications are essential to optimization of outcomes. The safe anaesthetic management of a child with OSA requires an anaesthetic technique tailored to the underlying aetiology and severity of OSA and the surgical procedure. This review focuses on the epidemiology, pathogenesis, and diagnosis of OSA, and the state-of-the-art and future directions in the perioperative management of children with OSA.

Obstructive Sleep Apnea in Adults

Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder characterized by repeated episodes of obstructed (apnea) or reduced (hypopnea) airflow in the upper airway during sleep. Obstructive sleep apnea results in variable arterial oxygen desaturations and arousals leading to sleep fragmentation. Most patients with OSA first come to the attention of a clinician when they complain of daytime sleepiness or when their bed partner reports loud snoring and witnessed episodes. Obstructive sleep apnea is associated with impaired quality of life, cardiovascular disease, metabolic syndrome, and motor vehicle accidents, yet the disorder remains undiagnosed in a significant portion of the population. Overnight polysomnography, whether facility-based or portable, is required for appropriate patient diagnosis. Portable monitoring can be used in patients with a high pre-test probability for moderate-to-severe OSA, who are without significant comorbidities. Management of OSA requires a long-term multidisciplinary approach. Continuous positive airway pressure (CPAP) remains the mainstay of treatment for patients with moderate-to-severe OSA. Oral appliances may be indicated in patients with mild-to-moderate OSA who do not wish to use CPAP. Surgical therapy is generally reserved for selected patients in whom CPAP or oral appliance are not an option.

Large-scale CFD simulations of airflow and particle deposition in lung airway

The flow fields in the small bronchial tubes are mostly laminar. However, they are quite complex mainly due to the geometrical effects of the lung airways. Asymmetry, nonplanarity and multiple generations are the main attributes of the lung airway geometry. There are total 23 generations of airways in human lung. The complexity of the airflow in the lung airway increases with an increasing number of generations. Particle deposition in bronchial tubes is strongly affected by these complex flow fields. Simulation of flow and particle deposition in multi-generational bronchial tube geometries is a major challenge because of the complexity of the geometry and size of the problem. The unsteady nature of inhale–exhale breathing cycles further complicates the problem. In this study, we simulate flows and particle deposition in an idealized lung geometry consisting of a ten-generation, nonplanar, bronchial tube model using our hybrid (finite element/finite volume), matrix free, parallel CaMEL solver. Steady-state inspiratory and unsteady flows were simulated with an inlet Reynolds number of 319. In this study, the large-scale CFD simulations for ten-generation bronchial tube model were successfully demonstrated. The particle transport was simulated using our Lagrangian based particle tracking model. The impact of unsteadiness on particle deposition was investigated by employing particle deposition efficiencies in each generation and particle destination maps. Particles were released at different inhalation times to investigate the unsteady effects. The results showed different particle deposition patterns for different particle release times. Particles released later in inhalation phase resulted in comparatively more particle deposition. The particle deposition before and after inhalation peak, which had identical inflow conditions, were observed to be significantly different due to the slight differences in strength of the vortices. Also, the results showed importance of geometry in later generations in particle deposition.

Numeric Simulation of the Upper Airway Structure and Airflow Dynamic Characteristics After Unilateral Complete Maxillary Resection

Numeric Simulation of the Upper Airway Structure and Airflow Dynamic Characteristics After Unilateral Complete Maxillary Resection

Comparative analysis of realistic CT-scan and simplified human airway models in airflow simulation

Efforts to model the human upper respiratory system have undergone many phases. Geometrical proximity to the realistic shape has been the subject of many research projects. In this study, three different geometries of the trachea and main bronchus were modelled, which were reconstructed from computed tomography (CT) scan images. The geometrical variations were named realistic, simplified and oversimplified. Realistic refers to the lifelike image taken from digital imaging and communications in medicine format CT scan images, simplified refers to the reconstructed image based on natural images without realistic details pertaining to the rough surfaces, and oversimplified describes the straight wall geometry of the airway. The characteristics of steady state flows with different flow rates were investigated, simulating three varied physical activities and passing through each model. The results agree with previous studies where simplified models are sufficient for providing comparable results for airflow in human airways. This work further suggests that, under most exercise conditions, the idealised oversimplified model is not favourable for simulating either airflow regimes or airflow with particle depositions. However, in terms of immediate analysis for the prediction of abnormalities of various dimensions of human airways, the oversimplified techniques may be used.

Numerical simulation for the upper airway flow characteristics of Chinese patients with OSAHS using CFD models

OSAHS is a common disease with many factors related to the etiology. Airflow plays an important role in the pathogenesis of OSAHS. Previous research has not yielded a sufficient understanding of the relationship between airflow in upper airway and the pathophysiology of OSAHS. Therefore, a better understanding of the flow inside the upper airway in an OSAHS patient is necessary. In this study, ten Chinese adults with OSAHS were recruited. We used the software MIMICS 13.1 to construct 3-dimensional (3-D) models based on the computer tomography scans of them. The numerical simulations were carried out using the software ANSYS 12.0. We found that during the inhalation phase, the vortices and turbulences were located in both the anterior part of the cavity and nasopharynx. But there is no vortex in the whole nasal cavity during the expiratory phase. The airflow velocity is much higher than that of the normal models. The distributions of pressure and wall shear stress are different in two phases. The maximum velocity, pressure and wall shear stress (WSS) are located in velopharynx. It is notable that a strong negative pressure region is found in pharyngeal airway. The maximum velocity is 19.26 ± 12.4 and 19.46 ± 13.1 m/s; the average pressure drop is 222.71 ± 208.84 and 238.5 ± 218.56 Pa and the maximum average WSS is 0.72 ± 0.58 and 1.01 ± 0.61 Pa in inspiratory and expiratory, respectively. The changes of airflow due to the structure changes play an important role in the occurrence of collapse and obstruction of the upper airway, especially, the abnormal pressure changes in velopharyngeal during both inspiratory and expiratory phases. We can say that the airway narrowing in the pharynx may be one of the most important factors driving airway collapse. In addition, the most collapsible region of the pharyngeal airway of the patient with OSAHS may be the velopharynx and oropharynx. In spite of limitations, our results can provide a basis for the further research. On this basis, more about the secret of the pathogenesis of the OSAHS will be revealed.

Rac1 Modulates Agonist-Induced Smooth Muscle Contraction

Smooth muscle is distributed in many organs, and plays a critical role in maintaining blood pressure in vasculature and airflow in airway and malfunction of the smooth muscle causes severe health problems. Smooth muscle contraction is primarily regulated by myosin light chain (MLC) phosphorylation, which is regulated by both Ca2+ dependent and Ca2+ independent pathways. Recent studies have revealed that MLC phosphatase (MLCP) plays a key role in the latter mechanism. MLCP activity is regulated by the phosphorylation of MYPT1, a myosin binding regulatory subunit of MLCP, and CPI-17, a MLCP specific inhibitor protein. Here we found novel signaling mechanism of controlling smooth muscle contraction induced by agonists. We found that agonist stimulation significantly activates Rac1 activity in smooth muscle, and the inhibition of Rac markedly decreases agonist induced force of arterial smooth muscle. Moreover, introduction of active Rac1 activates smooth muscle contraction, while dominant-negative Rac1 attenuates the agonist-induced contraction. Rac1 dependent change in contraction is accompanied by the change in MLC phosphorylation, MYPT1 phosphorylation and CPI-17 hosphorylation. Rac inhibitors activated MLCP activity, but not MLCK activity, suggesting that Rac1 dependent change in MLC phosphorylation is due to the change in MLCP activity. Rac inhibitors did not change RhoA and ROCK activities, unlike RhoA pathway. Interestingly, Rac1 inhibition induced the change in MYPT1/CPI-17 phosphatase activity. The result suggests that Rac1 dependent change in MYPT1/CPI-17 phosphorylation is due to the change in the phosphatase activity rather than the kinase activites that phopshorylate MYPT1 and CPI-17 such as ROCK. These results suggest that agonist induced change in MLCP activity in smooth muscle is concertedly regulated by RhoA pathway that modulates ROCK and Rac1 pathway that regulates MYPT1/CPI-17 phosphatases.

Micro-particles Transport and Deposition in Realistic Geometry of Human upper Airways

Realistic geometry of human upper airways from mouth to the end of trachea was reconstructed by implementing the CT-Scan images of a male subject. A computational model for analyzing the airflow in the airways was developed and several simulations were performed. To capture the anisotropy of the inhaled airflow in the upper airways, the Reynolds stress transport model of turbulence was used in these simulations. The simulation results for the inhalation rates of 15, 30 and 60 lit/min that represent, respectively, resting, normal and active conditions of human, were obtained.Micro particles transport and deposition in the realistic model of human upper airways were studied. Micro particles transport was analyzed using the Lagrangian particle trajectory approach. Since the mass fraction of inhaled particles was very small, the one-way coupling assumption was used. That is, the air flow carries the particles, but particles do not affect the airflow condition.The predicted deposition fractions of the particles of different sizes in the upper airways were compared with the available experimental data and good agreements were found. Comparison of the results of the deposition fraction obtained from the realistic model with the earlier simulations of the idealized geometry of the airways showed certain differences especially in regional depositions. Therefore, it was concluded that the realistic geometry must be used for more accurate evaluation of micro particle deposition rate especially for local and regional deposition.

Passive movement of human soft palate during respiration: A simulation of 3D fluid/structure interaction

This study reconstructed a three dimensional fluid/structure interaction (FSI) model to investigate the compliance of human soft palate during calm respiration. Magnetic resonance imaging scans of a healthy male subject were obtained for model reconstruction of the upper airway and the soft palate. The fluid domain consists of nasal cavity, nasopharynx and oropharynx. The airflow in upper airway was assumed as laminar and incompressible. The soft palate was assumed as linear elastic. The interface between airway and soft palate was the FSI interface. Sinusoidal variation of velocity magnitude was applied at the oropharynx corresponding to ventilation rate of 7.5L/min. Simulations of fluid model in upper airway, FSI models with palatal Young's modulus of 7539Pa and 3000Pa were carried out for two cycles of respiration. The results showed that the integrated shear forces over the FSI interface were much smaller than integrated pressure forces in all the three directions (axial, coronal and sagittal). The total integrated force in sagittal direction was much smaller than that of coronal and axial directions. The soft palate was almost static during inspiration but moved towards the posterior pharyngeal wall during expiration. In conclusion, the displacement of human soft palate during respiration was mainly driven by air pressure around the surface of the soft palate with minimal contribution of shear stress of the upper airway flow. Despite inspirational negative pressure, expiratory posterior movement of soft palate could be another factor for the induction of airway collapse.

Moving boundary simulation of airflow and micro-particle deposition in the human extra-thoracic airway under steady inspiration. Part I: Airflow

Airflow into the lung is the result of negative alveolar pressure caused by the simultaneous action of diaphragm contraction and rib cage expansion. However, all of the determinate CFD simulations on airflow and particle deposition in the human upper respiratory tract to date have employed a fixed boundary condition, i.e. uniform or axial symmetrical velocity profiles at the mouth inlet and outlet/opening boundary at the end of the airway. In this study, the realistic breathing mechanism, i.e. expansion of the pleural cavity, is mimicked by the fluid–structure interaction employing a junction box routine to assign the motion of the moving wall boundary at the bottom of the extra-thoracic airway model with an extra bell-mouthed tube. The airflow and particle deposition are investigated, particularly for the movable boundary cases, and compared with the fixed cases. In Part I, the flow characteristics which are important factors for particle deposition, i.e. pressure drop, turbulence intensity, secondary intensity and velocity profiles, are illustrated at three flow rates, as well as the detailed recirculation flow in the trachea region. Compared with the fixed boundary cases, several notable differences are found:(i) the velocity profiles at the mouth inlet are not uniform or axially symmetric, but askew with high-speed flow shifted to the upper wall of the mouth inlet tube, and a more evident recirculation zone occurs near the lower wall of the inlet tube; (ii) the pressure drop and turbulence intensity are lower and the secondary intensity is higher than that in the fixed boundary case because of the askew profile in the mouth cavity and modified recirculation flow in the trachea region; (iii) at three flow rates, the secondary intensities exhibit identical characteristics before the larynx where the turbulence fluctuations are very weak, but discrepancies are evident in the trachea region because of the high level of turbulence intensity and different pattern of recirculation zones; (iv) the length of the recirculation zones increase at three flow rates and the minor separation and reattachment occur in the middle portion of the recirculation flow, while the recirculation flow layer is divided into two parts at higher flow rates; (v) the peaks of the secondary flow intensity in the trachea region are located near the flow separation and reattachment points (both the major and minor) and the peaks of turbulence intensity in the trachea seem to correspond to the major separation and reattachment region.

Obstructive Sleep Apnea Severity Correlates with Cellular and Plasma Oxidative Stress Parameters and Affective Symptoms

Obstructive sleep apnea syndrome (OSAS) is considered a sleep-related respiratory disorder, characterized by repetitive episodes of complete (apnea) or partial (hypopnea) obstruction of airflow in the upper airway (UA) during sleep. The pathophysiology of upper airway obstruction in OSAS is multifactorial, leading to a chronic recurrent state of intermittent hypoxemia and reoxygenation during sleep, maintaining a state of oxidative stress, which seems to be the key to the pathophysiological manifestations of OSAS, and is associated with the development of a number of high morbidity-mortality systematic complications, such as obesity, type 2 diabetes, metabolic syndrome, and cardiovascular and neuropsychological diseases. This study is an open, cross-sectional, and comparative clinical trial, whose general objective was to assess the correlation between OSAS severity, oxidative stress markers, and the presence of affective symptoms (depressive and anxious) in OSAS patients. We studied 38 adult males, who had been diagnosed with OSAS by overnight polysomnography, between 18 and 60 years of age, divided into three groups: group 1-10 individuals with mild OSAS (AHI between 5 and 14.9/h), group 2-13 individuals with moderate OSAS (AHI between 15 and 30/h), and group 3-15 individuals with severe OSAS (AHI >30/h). All individuals were evaluated for level of subjective sleepiness using the Epworth Sleepiness Scale, for depressive and anxiety symptoms by the Hamilton Depression (HAM-D) and Anxiety (HAM-A) Scales, and for parameters of the oxidative stress state, measuring superoxide radical and serum nitrates and nitrites levels. There was a progressive and significant increase in the state of oxidative stress (p < 0.05), in the total score of depressive symptoms (p = 0.001) and in the overall score of anxiety symptoms (p = 0.004) directly proportional to the severity of apnea when comparing the mild group to the severe group. Positive correlations were identified between superoxide production and the apnea-hypopnea index (AHI) (r = 0.48), Epworth sleepiness score (r = 0.36), and Hamilton depression score (HAM-D) (r = 0.40); between serum nitrates and nitrites levels and SO(2) min (r = 0.44); and between the AHI and the HAM-D (r = 0.51) score and HAM-A (r = 0.40) score. Negative correlations were observed between the AHI and serum nitrates and nitrites levels (r = -0.42), between superoxide production and SO(2) min (r = -0.31), between serum nitrates and nitrites levels and HAM-D (r = -0.50) and HAM-A (-0.42) scores, and between SO(2) min and HAM-D (r = -0.48) and HAM-A (r = -0.40) scores. According to the results of this study, we can conclude that (1) individuals with OSAS show an increase in the production of superoxide radical and a decrease in serum nitrates and nitrites levels, which are objective signs of a state of oxidative stress. (2) The more severe the OSAS, the more fragmented the sleep and the greater the nocturnal hypoxemia, the more severe is the oxidative stress state and the greater is the incidence of daytime symptoms, especially sleepiness and depressive and anxiety symptoms. Future studies might explore the investigation of oxidative stress parameters as an alternative approach to anticipate symptoms, measure prognosis, and monitor OSAS progression or treatment response.

A threshold lung volume for optimal mechanical effects on upper airway airflow dynamics: studies in an anesthetized rabbit model

Increasing lung volume improves upper airway airflow dynamics via passive mechanisms such as reducing upper airway extraluminal tissue pressures (ETP) and increasing longitudinal tension via tracheal displacement. We hypothesized a threshold lung volume for optimal mechanical effects on upper airway airflow dynamics. Seven supine, anesthetized, spontaneously breathing New Zealand White rabbits were studied. Extrathoracic pressure was altered, and lung volume change, airflow, pharyngeal pressure, ETP laterally (ETPlat) and anteriorly (ETPant), tracheal displacement, and sternohyoid muscle activity (EMG%max) monitored. Airflow dynamics were quantified via peak inspiratory airflow, flow limitation upper airway resistance, and conductance. Every 10-ml lung volume increase resulted in caudal tracheal displacement of 2.1 ± 0.4 mm (mean ± SE), decreased ETPlat by 0.7 ± 0.3 cmH(2)O, increased peak inspiratory airflow of 22.8 ± 2.6% baseline (all P < 0.02), and no significant change in ETPant or EMG%max. Flow limitation was present in most rabbits at baseline, and abolished 15.7 ± 10.5 ml above baseline. Every 10-ml lung volume decrease resulted in cranial tracheal displacement of 2.6 ± 0.4 mm, increased ETPant by 0.9 ± 0.2 cmH(2)O, ETPlat was unchanged, increased EMG%max of 11.1 ± 0.3%, and a reduction in peak inspiratory airflow of 10.8 ± 1.0%baseline (all P < 0.01). Lung volume, resistance, and conductance relationships were described by exponential functions. In conclusion, increasing lung volume displaced the trachea caudally, reduced ETP, abolished flow limitation, but had little effect on resistance or conductance, whereas decreasing lung volume resulted in cranial tracheal displacement, increased ETP and increased resistance, and reduced conductance, and flow limitation persisted despite increased muscle activity. We conclude that there is a threshold for lung volume influences on upper airway airflow dynamics.

Comparing Performance of Three Oscillating Positive Expiratory Pressure Devices at Similar Amplitude and Frequencies of Oscillations on Displacement of Mucus Inside Trachea During Cough

Performance of Flutter® (Axcan Scandipharm Inc, Birmingham, AL), Acapella® (Smiths Medicals Inc, Rockland, MA) and Quake® (Thayer Medical, Tucson, AZ) were compared at similar frequencies and amplitudes of oscillations at nine angles of the device in clearing simulated mucus inside a tracheal model (trachea) oriented at three angles with or without simulated constrictions in airway upstream of trachea. Displacement of 0.4mL of simulated mucus prepared with viscoelastic properties similar to healthy individuals (syrup-like) or patients with COPD (gel-like) using locust bean gum(LBG) solution (0.38g LBG in 100mL water) cross-linked with 3mL or 12mL borax solution (0.02 molar), respectively were measured inside trachea during coughs of 300ms at low cough velocity (15±0.5m/s) generated using a computer controlled solenoid valve. Oscillations were superimposed on cough by connecting the oscillator device to the outlet of the trachea. Frequency and amplitude of oscillations generated by Quake and Acapella and resulting mucus displacement were independent of angle of oscillator, while amplitude of oscillations and resulting mucus displacement generated by Flutter, increased up to 30o upward and 20o downward angles of Flutter from horizontal but decreased significantly thereafter. Displacement with Quake increased significantly with frequencies of oscillations up to 25 Hz and decreased thereafter but increased with amplitudes of oscillations up to 22±4.7 m/s. Quake showed significantly larger displacements than Flutter and Acapella at equal frequencies and amplitudes (p<0.05). Displacements were significantly larger with trachea positioned 30o upwards than horizontal or 20o downwards (p<0.0001). Displacement was the greatest for gel-like mucus than syrup-like (p<0.0001). Airway constrictions upstream resulted in enhanced displacement of mucus (p<0.0001). Mucus clearance can be significantly enhanced by coughing through oscillating positive expiratory devices that generate high amplitude oscillations at moderate frequencies, increasing frontal depths of mucus facing airflow and slightly increasing resistance to airflow in airways in COPD patients.

Mechanism of Convective Heat Transfer of Airflow in Deep Airway

With the increase of mining depth, an investigation of the convective heat transfer of airflow in deep airway is urgently required. The velocity and temperature distribution were derived by using the turbulence model for smooth tube. In order to simplify calculation and avoid the complicated calculation of integration, with the help of velocity-temperature distribution analogy, the criterion equation of convective heat transfer was obtained by using the model of constant heat flux. The coefficient of convective heat transfer between airflow and airway was calculated, and criterion correlation of convective heat transfer was regressed according to test data. Test results show that the axial temperature distribution of airflow is linear, which is encouraging agreement with theoretical calculating results. Hence model of constant heat flux is a viable method for studying the convective heat transfer of airflow in deep airway.

Residents’ journal review

Residents’ journal review

Impact of Inhaled Corticosteroids on Small Airway Airflow Obstruction in Asthmatic Children

RATIONALE: Forced expiratory flow between 25 and 75% of vital capacity (FEF 25-75) is a measure of small airway airflow obstruction. Asthmatic children may have impaired FEF 25-75 as the sole spirometric abnormality. The clinical benefits of inhaled corticosteroids (ICS) in relieving small airway airflow obstruction in asthmatic children have been difficult to assess.