Mechanical study of blood flow through a permeable capillary with slippery wall.

This research presents the mechanical behavior of blood flow through capillary having smooth inner surface. In this study modelling of blood flow via permeable and lubricated capillary caused by nutrients re-absorption has been done by the help of laws of momentum and mass. The nutrients re-absorption is assumed to be constant and inner walls of the capillary are smooth and slippery therefore slip condition on the velocity and constant rate in vertical direction at the wall has considered. The Kelvin Voigt model is employed to simulate blood flow via capillaries, and results for pressure, blood flow pattern, and shear force necessary for blood flow are discovered by recursive approach. Numerical results for nutrient re-absorption from the blood and impact of smooth and slippery surfaces on blood flow are shown through graphs. The novelty of the research invents that the smoothness and slickness of capillary wall is a crucial presumption to examine the blood as non-Newtonian fluid via capillary.

The hydrodyanamics of gravity-driven vessel drainage of third order fluid using perturbation method.

In this work, tank drainage phenomena for in-compressible and isothermal fluid having unsteady fluid flow for third order fluid is studied. Analytical solution of the proposed problem is obtained using perturbation method subject to proper boundary conditions. No-slip condition is used because of fluid will have zero velocity relative to a solid boundary. Object of this work is to find out the velocity profile, flow rate, time required to empty a tank (time efflux) and mathematical relation of time and depth of the tank. Influence of different parameter over velocity profile, effect of radius of the tank over depth, effect of radius of piper over flow rate and effect of depth over flow rate are examined graphically using mathematica. Velocity profile of this model is compared with newtonian fluid's while assuming epsilon as a zero using graph and table from which it is clear that third order fluid posses greater velocity then Newtonian fluid.

Synthesis of silver nanoparticles using Emilia sonchifolia plant for treatment of bloodstream diseases caused by Escherichia coli.

OBJECTIVES: Among infectious diseases, bloodstream infection (BSI) caused by gram-negative bacteria (E. coli) is the leading cause of death worldwide. However, the bacteria have produced resistance to many of these antibiotics. Thus, the present study aimed to develop silver nanoparticles (AgNPs) loaded with Emilia sonchifolia (ES) extract (ES-AgNPs) to treat BSI efficiently. METHODS: AgNPs were synthesized by reduction of silver nitrate (AgNO3) solution by ES extract. Furthermore, these ES-AgNPs were characterized for particle size and zeta potential, crystallinity by powder X-ray diffraction (P-XRD) technique, in vitro antibacterial activity, time-kill assay, film bio adhesion, and fluorescence assay. RESULTS: Surface plasmon resonance (SPR) has been used to confirm the formation of AgNPs by seeing a shift in colour to dark-brown. The ES-AgNPs displayed a mean particle size of 137±3nm (PDI of 0.168±0.02) and zeta potential of 18.2±0.8mV. Furthermore, according to P-XRD results, the developed AgNPs are highly crystalline. The ES-AgNPs showed effective antibacterial action against E. coli with minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of 0.4±0.02µg/mL and 0.8±0.03µg/mL, respectively. In addition, ES-AgNPs inhibited biofilm formation and bacterial adhesion in a dose-dependent manner with 100% inhibition obtained in 48h at MBC. CONCLUSIONS: Present research work revealed that the ES-AgNPs obtained by green synthesis holds a prominent antibacterial activity in the treatment of BSIs caused by E. coli and they may be used as a competent substitute for current treatments. However, further, in vivo antibacterial studies are required to establish its efficacy in the treatment of BSIs.

Assessment of attitude and hesitancy toward vaccine against COVID-19 in a Pakistani population: A mix methods survey.

Objective: The objective of this study was to assess the attitude and hesitancy toward vaccine against COVID-19 in a Pakistani Population. Materials and methods: A mix-method, prospective study was conducted and adults (aged ≥18 years) residing in Pakistan were invited to participate. The questionnaire was prepared, hosted in Google Forms and circulated through electronic platforms and was also available to be done in in-person. Data was compiled from 15th September to 30th November 2020. Results: The response rate was 80%. A total of 1003 participants were included in the final analysis. Of them, 75% completed survey questionnaire online, while remaining 25% responded in-person. The mean age of the participants was 29.62 ± 10.47 years. The majority of participants were females; 60.9% (n = 611). 57.02% (n = 572) of the participants were employed at the time of survey. Overall, 70.68% (n = 709) of the participants had previous experience of vaccines such as the flu vaccine Only 4.9% (n = 49) participants thought that they will be seriously ill from COVID-19 within six months and 39% (n = 392) participants were confident that they will get COVID-19. A total of 71.29% of the participants reported they would consider getting vaccinated once available. There was statistical association between gender and getting vaccinated (P < 0.001). Conclusion: This study demonstrated that majority of the participants showed positive attitude toward considering COVID-19 vaccine. However awareness with informed knowledge of efficacy, possible adverse effects and cost would be of added great value to increase the real response of Pakistani population toward COVID-19 vaccination.

Objetivo: El objetivo de este estudio fue evaluar la actitud y la renuencia hacia la vacuna frente a la COVID-19 en una población paquistaní. Materiales y métodos: Se realizó un estudio prospectivo de método mixto, invitándose a participar a personas adultas (edad ≥18 años) residentes en Paquistán. Se preparó el cuestionario, que se alojó en Google Forms y se hizo circular a través de plataformas electrónicas, pudiendo realizarse también de manera personal. Los datos se recopilaron desde el 15 de septiembre al 30 de noviembre de 2020. Resultados: La tasa de respuesta fue del 80%. El análisis final incluyó un total de 1.003 participantes, de los cuales el 75% completó el cuestionario-encuesta online, mientras que el 25% respondió en persona. La edad media de los participantes fue de 29,62 ± 10,47 años. La mayoría de los participantes eran mujeres: el 60,9% (n = 611). El 57,02% (n = 572) de los participantes tenía empleo en el momento de la encuesta. En general, el 70,68% (n = 709) de los participantes tenía experiencia previa sobre vacunas tales como la vacuna frente a la gripe. Solo el 4,9% (n = 49) de los participantes pensaba que padecerían la COVID-19 de forma grave en el plazo de seis meses, y el 39% (n = 392) de los participantes estaba seguro de que se contagiaría de dicha enfermedad. El 71,29% de los participantes reportó que consideraría recibir la vacuna una vez que se dispusiera de la misma. Existió una asociación estadística entre el sexo y el ser vacunado (P< 0,001). Conclusión: Este estudio demostró que la mayoría de los participantes mostró una actitud positiva hacia la consideración de la vacuna frente a la COVID-19. Sin embargo, la concienciación sobre el conocimiento informado de la vacuna, los posibles efectos adversos y el coste supondrían un gran valor añadido al incremento de la respuesta real de la población paquistaní hacia la vacuna frente a la COVID-19.

Flow analysis of Carreau fluid model induced by the ciliary cells, smooth muscle cells and pressure gradient at the ampullar region entrance.

This theoretical analysis considers a biomechanical model in which the Carreau fluid model characterizes the viscoelastic nature of growing human embryo and secreted fluid. This model incorporates transport mechanisms that involve the swaying motions of ciliary cells, peristaltic contractions of smooth muscle cells and pressure gradient at the ampullar region entrance. Series form solutions of the resulting partial differential equations are obtained using the regular perturbation method. A theoretical estimate of effects of the condition of pressure gradient, geometric parameters and fluid model parameters on the flow variables that have relevance to the problem of growing embryo transport in the human fallopian tube is presented through the discussion of graphs. Furthermore, an analogy between the linearly viscous fluid, and the shear thinning and shear thickening characteristics of the Carreau fluid model is also presented. The pertinence of the obtained results with growing embryo transport in the human fallopian tube revealed that when shear thickening characteristics of the Carreau fluid model are considered then complete mitotic divisions take place properly with an estimated appropriate residue time about 3-4 days. Smaller size trapped boluses of the secreted fluid make the smooth forwarding of the growing embryo in the human fallopian tube when shear thinning characteristics of the Carreau fluid model are taken into account. Key modulators: progesterone ([Formula: see text] and estradiol ([Formula: see text]), prostaglandin [Formula: see text] ([Formula: see text]) and prostaglandin [Formula: see text] ([Formula: see text]) constraint the growing embryo transport.

Application of creeping flow through a linearly absorbing slit filled with porous medium to diseased renal tubules.

In this paper, we have discussed the flow of a Newtonian fluid through a slit filled with porous medium and linearly reabsorbing porous walls. The study is motivated by fluid flow in diseased renal tubules in a kidney. Due to diseases, some fibrous material, fatty substances and solid waste particles, etc., may get suspended in tubule channel as well as on the pores of the wall, resulting in the porous filling in the slit and biofouling, respectively. In this study, the absorption at the wall is assumed to follow a linear pattern and the fluid is assumed to be entering the channel at a prescribed initial flow rate. The problem of the two-dimensional fluid flow is formulated using stream function, and inverse solution method is applied to obtain an exact solution of the fourth-order compatibility equation. Some special cases are also deduced from the obtained results and compared with available results from literature. Expressions for various physically relevant quantities like fluid velocities, volume flow rate, fractional reabsorption, leakage flux and pressure distribution are obtained. The results are used to demonstrate how medium porosity and biofouling parameter may affect average pressure differences in the renal tubules of a rat kidney. Finally, the results are presented graphically and effects of changing various parameters on the flow are analysed. We have also deduced some special cases when the wall reabsorption is uniform, and when there is no medium porosity. We have shown these special cases match with the already present results in the literature.

Mathematical assessment of the spermatozoa transport through couple stress fluid in an asymmetric human cervical canal.

Swimming of spermatozoa through couple stress fluid in an asymmetric human cervical canal is investigated in the present theoretical analysis. A couple of fourth-order partial differential equations arising from the mathematical modelling of the proposed model is solved analytically. Flow variables like pressure gradient, propulsive velocity, mucus velocity and time mean flow rate are analysed for the pertinent parameters. Conspicuous features of the pumping characteristics are explored. It is found that pressure rise facilitates the motion of spermatozoa to fertilize an ovum in the female reproductive tract, whereas pressure drop by inverting the direction of spermatozoa controls the probability of pregnancy. Maximal propulsive velocity of the spermatozoa is reported in the absence of travelling waves along the cervical walls. Minute impact of phase difference on propulsive velocity is evident. An analogy of the current analysis with the existing literature is also made.

A Jeffrey Fluid Model for a Porous-walled Channel: Application to Flat Plate Dialyzer.

Creeping motion of a Jeffrey fluid in a small width porous-walled channel is presented with an application to flow in flat plate hemodialyzer. Darcy's law is used to characterize the fluid leakage through channel walls. Using suitable physical approximations, approximate analytical solution of equations of motion is obtained by employing perturbation method. Expressions for velocity field and the hydrostatic pressure are obtained. Effects of filtration coefficient, the inlet pressure and Jeffrey fluid parameters on the flow characteristics are discussed graphically. The derived results are used to study the flow of filtrate in a flat plat hemodialyzer. Using the derived solutions, theoretical values of the filtration rate and the mean pressure difference in the hemodialyzer are calculated. On comparing the computed results with the available experimental data, a reasonable agreement between the two is found. It is concluded that the presented model can be used to study the hydrodynamical aspects of the fluid flow in a flat plate hemodialyzer.

Effect of nano-particles on MHD flow of tangent hyperbolic fluid in a ciliated tube: an application to fallopian tube.

This study shows the effects of magnetic field and copper nanoparticles on the flow of tangent hyperbolic fluid (blood) through a ciliated tube (fallopian tube). The present study will be very helpful for those patients who are facing blood clotting in fallopian tube that may cause for infertility or cancer. The nanoparticles and magnetic field are very helpful to break the clots in blood flowing in fallopian tube. Since blood flows in fallopian tube due to ciliary movement, therefore medicines containing copper nanoparticles and magnetic field with radiation therapy help to improve the patient. Ciliary movement has a particular pattern of motion i.e., metachronal wavy motion which helps to fluid flow. For the forced convective MHD flow of tangent hyperbolic nano-fluid, momentum and energy equations are solved by the small Reynolds' number approximation and Adomian decomposition method by constructing the recursive relation of ADM and solved by software "MATHEMATICA". The effects of parameters such as nanoparticle volume fraction, Hartmann number, entropy generation and Bejan's number have been discussed through graphs plotted in software "MATHEMATICA". It is found that blood flow is accelerated and heat transfer enhancement is maximum in the presence of nano particles, also magnetic effects accelerates the blood flow and help to enhance the heat transfer whereas the presence of porous medium increases the fluid's velocity and reduce the transfer of heat through fluid flow.

Analysis of the peristaltic-ciliary flow of Johnson-Segalman fluid induced by peristalsis-cilia of the human fallopian tube.

The present prospective theoretical analysis concerns with the peristalsis-cilia induced transport of a developing embryo from ampulla to intramural, in the human fallopian tube. A model of peristalsis-cilia induced flow of the Johnson-Segalman fluid within fallopian tubal fluid in a finite two dimensional narrow tube is developed. We solved highly non-linear PDE emerging from the modeling of proposed model using perturbation method. The series expressions for flow variables like axial and radial velocities, pressure gradient, stream function, volume flow rate and time mean volume flow rate are derived. The numerical integration is performed for appropriate residue time over tube length and pressure difference over wavelength. The analysis delineated that, involved parameters and constants have vice versa effects on axial velocity and appropriate residue time over tube length. Striking features of the pumping characteristics and the trapping phenomenon are discussed in detail. Furthermore, comparison of the peristaltic flow with the peristaltic-ciliary flow and Johnson-Segalman fluid with the linearly viscous fluid is made. It is revealed that appropriate residue time of the Johnson-Segalman fluid in the narrow tube is 3-4 days, which agreed with the time taken by the developing embryo from ampulla to intramural, in the human fallopian tube.

Analysis of a self-propelling sheet with heat transfer through non-isothermal fluid in an inclined human cervical canal.

The present theoretical analysis deals with biomechanics of the self-propulsion of a swimming sheet with heat transfer through non-isothermal fluid filling an inclined human cervical canal. Partial differential equations arising from the mathematical modeling of the proposed model are solved analytically. Flow variables like pressure gradient, propulsive velocity, fluid velocity, time mean flow rate, fluid temperature, and heat-transfer coefficients are analyzed for the pertinent parameters. Striking features of the pumping characteristics are explored. Propulsive velocity of the swimming sheet becomes faster for lower Froude number, higher Reynolds number, and for a vertical channel. Temperature and peak value of the heat-transfer coefficients below the swimming sheet showed an increase by the increment of Brinkmann number, inclination, pressure difference over wavelength, and Reynolds number whereas these quantities decrease with increasing Froude number. Aforesaid parameters have shown opposite effects on the peak value of the heat-transfer coefficients below and above the swimming sheet. Relevance of the current results to the spermatozoa transport with heat transfer through non-isothermal cervical mucus filling an inclined human cervical canal is also explored.

A mathematical model for the flow of a Casson fluid due to metachronal beating of cilia in a tube.

A mathematical model is developed to study the transport mechanism of a Casson fluid flow inspired by the metachronal coordination between the beating cilia in a cylindrical tube. A two-dimensional system of nonlinear equations governing the flow problem is formulated by using axisymmetric cylindrical coordinates and then simplified by employing the long wavelength and low Reynolds number assumptions. Exact solutions are derived for the velocity components, the axial pressure gradient, and the stream function. However, the expressions for the pressure rise and the volume flow rate are evaluated numerically. The features of the flow characteristics such as pumping and trapping are illustrated and discussed with the help of graphs. It is observed that the volume flow rate is influenced significantly by the width of plug flow region H p as well as the cilia length parameter ε. The analysis is also applied and compared with the estimated value of the volume flow rate of epididymal fluid in the ductus efferentes of the human male reproductive tract.

Analysis of Eyring-Powell fluid in helical screw rheometer.

This paper aims to study the flow of an incompressible, isothermal Eyring-Powell fluid in a helical screw rheometer. The complicated geometry of the helical screw rheometer is simplified by "unwrapping or flattening" the channel, lands, and the outside rotating barrel, assuming the width of the channel is larger as compared to the depth. The developed second order nonlinear differential equations are solved by using Adomian decomposition method. Analytical expressions are obtained for the velocity profiles, shear stresses, shear at wall, force exerted on fluid, volume flow rates, and average velocity. The effect of non-Newtonian parameters, pressure gradients, and flight angle on the velocity profiles is noticed with the help of graphical representation. The observation confirmed the vital role of involved parameters during the extrusion process.

Testosterone modulates gene expression pathways regulating nutrient accumulation, glucose metabolism and protein turnover in mouse skeletal muscle.

Testosterone regulates energy metabolism and skeletal muscle mass in males, but the molecular mechanisms are not fully understood. This study investigated the response of skeletal muscle to castration and testosterone replacement in 8-week-old male mice. Using microarray analyses of mRNA levels in gastrocnemius muscle, 91 genes were found to be negatively regulated by testosterone and 68 genes were positively regulated. The mRNA levels of the insulin signalling suppressor molecule Grb10 and the glycogen synthesis inhibitors, protein phosphatase inhibitor-1 and phosphorylase kinase-γ, were negatively regulated by testosterone. The insulin-sensitive glucose and amino acid transporters, Glut3 and SAT2, the lipodystrophy gene, Lpin1 and protein targeting to glycogen were positively regulated. These changes would be expected to increase nutrient availability and sensing within skeletal muscle, increase metabolic rate and carbohydrate utilization and promote glycogen accumulation. The observed positive regulation of atrogin-1 (Fbxo32) by testosterone could be explained by the phosphorylation of Akt and Foxo3a, as determined by Western blotting. Testosterone prevented the castration-induced increase in interleukin-1α, the decrease in interferon-γ and the atrophy of the levator ani muscle, which were all correlated with testosterone-regulated gene expression. These findings identify specific mechanisms by which testosterone may regulate skeletal muscle glucose and protein metabolism.

Knowledge, attitudes and practices regarding tuberculosis in two districts of Punjab, Pakistan.

SETTING: Pakistan ranks eighth among the world's highest tuberculosis (TB) burden countries, and Punjab province accounts for 60% of TB cases nationally. OBJECTIVE: To explore knowledge, attitudes and practices regarding TB in the general population of two districts of Punjab province, and the effect of socio-economic determinants. DESIGN: In a cross-sectional survey, subjects aged > or =20 years were randomly selected using multistage cluster sampling and interviewed. A knowledge score was formulated based on nine questions. Bivariate analysis using the chi(2) test was employed to independently correlate socio-economic factors with understanding of disease and information sources. Attitudes, practices and information sources were also compared with TB knowledge. RESULTS: Forty-two per cent of the surveyed population had good knowledge about TB, which was associated with better education, high income and good housing (all P < 0.001). Despite the fact that the majority (82.2%) knew about correct treatment, less than half (48.8%) were aware that diagnosis and treatment were free. Intended health-seeking behaviour was determined by better education (P = 0.011), good housing (P = 0.004) and good knowledge about TB (P < 0.001). Television (69.4%) and health workers (43.6%) were the main sources of information. CONCLUSION: Socio-economic factors should be considered when designing communication strategies and prioritising TB prevention and control interventions.

Generation of <7 fs pulses at 800 nm from a blue-pumped optical parametric amplifier at degeneracy.

We generate ultrabroadband pulses at 800 nm from an optical parametric amplifier (OPA) pumped by the second harmonic of a Ti:sapphire system and working at degeneracy. The OPA is seeded by a white-light continuum generated from a near-IR OPA pumped by the same laser. Nearly transform-limited <7 fs pulses, fully characterized in amplitude and phase, are obtained with a chirped mirror compressor. The system fills the gap around 800 nm for broadband continuum seeded OPAs pumped by Ti:sapphire-based sources.

In vitro monitoring of rabbit anterior cruciate ligament damage by acoustic emission.

Anterior cruciate ligament (ACL) rupture is a major clinical problem leading to instability and degeneration of the knee joint. The problem is compounded by the limited ability of the ACL to heal when ruptured. The existing knowledge regarding the way the ACL ruptures is limited, and this investigation is an attempt to understand the nature of the ruptures using the rabbit as a model. A total of 16 rabbit tibia-ACL-femur complexes were stretched in tension to complete rupture. Four specimens were stretched to failure at a displacement rate of 0.5 mm/min and 12 specimens at 10 mm/min. Acoustic emission (AE) transducers were placed on both the tibia and the femur, and stress wave signals generated during the tensile test were recorded. Fibre fractures produced the highest amplitude signals with a relatively longer rise time. Other failure modes such as matrix failure and debonding produced lower amplitude signals with shorter rise times. We also noted that few events were recorded during the initial period of tensile loading (the elastic phase). The activity then increased significantly after maximum load was reached. The location information provided by the acoustic emission system was consistent with the final site of rupture. We have shown that AE can be used to characterise ligament damage, with fibre pull-outs and fibre fracture producing the highest signal amplitudes.

Long-term effect of perfluorocarbon distension on the lung.

BACKGROUND/PURPOSE: We have demonstrated previously that postnatal lung growth can be accelerated by continuous intrapulmonary distension with perfluorocarbon (PFC). The purpose of this study was to examine the effect of PFC distension on long-term lung function and to determine if shorter periods of lung distension would be sufficient to stimulate growth. METHODS: Eight neonatal lambs underwent a right thoracotomy. The superior segment of the right upper lobe of the experimental group (n = 5) was isolated and distended with PFC to an intrabronchial pressure of 7 to 10 mm Hg. The inferior segment was removed. After a 7-day distension period (the maximum period of exposure currently allowed for humans), the experimental animals underwent removal of the intrabronchial catheter and surgical closure of the bronchial stump. Control animals (n = 3) underwent right upper lobe inferior segmentectomy alone. Animals were allowed to breathe spontaneously and reach 3 to 6 months of age. Before death, all animals were evaluated by chest radiographs and ventilation-perfusion scans. Pulmonary venous blood gas levels were obtained. Lungs were harvested and airway fixed for morphometric analysis. RESULTS: Chest radiographs of the experimental group showed variable amounts of intrapleural and interstitial PFC but were otherwise normal. Results of ventilation/perfusion (VQ) scans of all experimental animals were normal. On retrieval, the right upper lobe of experimental animals appeared slightly hyperinflated compared with controls. Right upper lobe pulmonary vein PaO2 to left pulmonary vein PaO2 ratio was comparable in experimental and control animals (1.2 +/- .41 v 0.92 +/- .15). DNA to protein ratios were slightly higher in the right upper lobes of experimental animals, however, the difference was not statistically significant (.64 +/- .11 v .42 +/- .03). On histological evaluation, the airway epithelium and alveoli of the right upper lobe of experimental animals appeared normal. Lung morphometry results showed no statistically significant differences in alveolar number between experimental and control animals. CONCLUSIONS: From these preliminary data we conclude that (1) lung architecture is preserved in juvenile animals subjected to intrapulmonary PFC distension as neonates, (2) lung function is preserved in the lobar segment after PFC distension, and (3) intrapulmonary PFC distension appears to be safe at 3 to 6 months follow-up. However, 7 days of PFC distension is insufficient to promote lung growth.

The use of expandable metallic stents for acute tracheal stenosis in the growing lamb.

PURPOSE: Expandable metallic stents (Palmaz stents) have been used in the treatment of tracheobronchial obstruction in children and adults. The authors investigated their utility in the management of acute airway stenosis in a growing animal model. METHODS: A model for tracheal stenosis was developed in young lambs (mean age, 4 weeks; mean weight, 8.6 kg). Via an anterior tracheotomy, a circumferential mucosal injury to the trachea was produced with electrocautery in 31 lambs. In the control group (n = 10) no further intervention was used. In the treatment groups, either serial balloon dilatation of the stricture was performed (n = 6), or expandable metallic stents were inserted across the stricture (n = 15). All animals were monitored daily for signs of respiratory distress. Body weights, fluoroscopic airway measurements and rigid bronchoscopy were performed at least weekly. RESULTS: The average weekly rate of airway growth was 8.2% +/- 5.5% of the tracheal cross-sectional area (CSA). All animals displayed severe stenosis (mean, 90.2% +/- 7.5% of CSA) within 13.1 +/- 4 days after the injury. All animals in the control group had severe respiratory distress, weight loss and died within 14.6 +/- 2.8 days after injury. Serial balloon dilatation of the stricture alone failed to relieve symptoms in all six animals in this group, who died within 20 +/- 1 days after the injury, despite two to three dilatations each. With placement of expandable metallic stents, only 3 of 15 lambs died (two of pneumonia, one of iatrogenic perforation). The remaining 12 remained symptom-free and gained weight during a 2-month follow-up period. However, fluoroscopic examination showed partial collapse of the stents in all of these animals (mean, 44.7% +/- 21.6% of CSA) requiring an average of 2 +/- 0.7 bronchoscopic dilatations. Pathological evaluation showed more pronounced granulation tissue in the stented animals. CONCLUSIONS: The authors conclude that expandable metallic stents provide an effective tool in the management of acute tracheal stenosis. However, airway growth, tissue reaction, and the mechanical properties of the stent require close monitoring and stent adjustment.