RESUMO
The nasal airway is an extremely complex structure, therefore grid generation for numerical prediction of airflow in the nasal cavity is time-consuming. This paper describes the development of a voxel-based model with a Cartesian structured grid, which is characterized by robust and automatic grid generation, and the simulation of the airflow and air-conditioning in an individual human nasal airway. Computed tomography images of a healthy adult nose were used to reconstruct a virtual three-dimensional model of the nasal airway. Simulations of quiet restful inspiratory flow were then performed using a Neumann boundary condition for the energy equation to adequately resolve the flow and heat transfer. General agreements of airflow patterns, which were a high-speed jet posterior to the nasal valve and recirculating flow that occupied the anterior part of the upper cavity, and temperature distributions of the airflow and septum wall were confirmed by comparing in-vivo measurements with numerical simulation results.
Assuntos
Simulação por Computador , Cavidade Nasal/fisiologia , Reologia , Temperatura , Humanos , Septo Nasal/diagnóstico por imagem , Septo Nasal/fisiologia , Nasofaringe/diagnóstico por imagem , Nasofaringe/fisiologia , Análise Numérica Assistida por Computador , Tomografia Computadorizada por Raios XRESUMO
The energy needed to drive airflow through the trachea normally constitutes a minor component of the work of breathing. However, with progressive tracheal compression, patient subjective symptoms can include severe breathing difficulties. Many patients suffer multiple respiratory co-morbidities and so it is important to assess compression effects when evaluating the need for surgery. This work describes the use of computational prediction to determine airflow resistance in compressed tracheal geometries reconstructed from a series of CT scans. Using energy flux analysis, the regions that contribute the most to airway resistance during inhalation are identified. The principal such region is where flow emerging from the zone of maximum constriction undergoes breakup and turbulent mixing. Secondary regions are also found below the tongue base and around the glottis, with overall airway resistance scaling nearly quadratically with flow rate. Since the anatomical extent of the imaged airway varied between scans-as commonly occurs with clinical data and when assessing reported differences between research studies-the effect of sub-glottic inflow truncation is considered. Analysis shows truncation alters the location of jet breakup and weakly influences the pattern of pressure recovery. Tests also show that placing a simple artificial glottis in the inflow to a truncated model can replicate patterns of energy loss in more extensive models, suggesting a means to assess sensitivity to domain truncation in tracheal airflow simulations.
Assuntos
Resistência das Vias Respiratórias , Simulação por Computador , Modelos Biológicos , Ventilação Pulmonar , Mecânica Respiratória , Tomografia Computadorizada por Raios X , Traqueia , Feminino , Humanos , Masculino , Traqueia/diagnóstico por imagem , Traqueia/fisiopatologia , Traqueia/cirurgiaRESUMO
This paper describes the simulation of airflow in human nasal airways using voxel-based modeling characterized by robust, automatic, and objective grid generation. Computed tomography scans of a healthy adult nose are used to reconstruct 3D virtual models of the nasal airways. Voxel-based simulations of restful inspiratory flow are then performed using various mesh sizes to determine the level of granularity required to adequately resolve the airflow. For meshes with close voxel spacings, the model successfully reconstructs the nasal structure and predicts the overall pressure drop through the nasal cavity.
Assuntos
Modelos Biológicos , Cavidade Nasal/fisiologia , Ventilação Pulmonar/fisiologia , Simulação por Computador , Humanos , Hidrodinâmica , Masculino , Pessoa de Meia-Idade , Cavidade Nasal/diagnóstico por imagem , Faringe/fisiologia , Pressão , Tomografia Computadorizada por Raios XRESUMO
We visualized pulmonary acini in the core regions of the mouse lung in situ using synchrotron refraction-enhanced computed tomography (CT) and evaluated their kinematics during quasi-static inflation. This CT system (with a cube voxel of 2.8 µm) allows excellent visualization of not just the conducting airways, but also the alveolar ducts and sacs, and tracking of the acinar shape and its deformation during inflation. The kinematics of individual alveoli and alveolar clusters with a group of terminal alveoli is influenced not only by the connecting alveolar duct and alveoli, but also by the neighboring structures. Acinar volume was not a linear function of lung volume. The alveolar duct diameter changed dramatically during inflation at low pressures and remained relatively constant above an airway pressure of â¼8 cmH2O during inflation. The ratio of acinar surface area to acinar volume indicates that acinar distension during low-pressure inflation differed from that during inflation over a higher pressure range; in particular, acinar deformation was accordion-like during low-pressure inflation. These results indicated that the alveoli and duct expand differently as total acinar volume increases and that the alveolar duct may expand predominantly during low-pressure inflation. Our findings suggest that acinar deformation in the core regions of the lung is complex and heterogeneous.
Assuntos
Pulmão/fisiologia , Alvéolos Pulmonares/fisiologia , Animais , Inflação , Masculino , Camundongos , Síncrotrons , Tomografia Computadorizada por Raios X/métodosRESUMO
Primary blast lung injury after explosions has been well described in the literature. A case of injury to the lung, after a shotgun wound to the head, similar to primary blast lung, is presented. Histological appearances of the lung revealed alveolar over distension, rupture and intra-alveolar hemorrhage. Primary blast lung injury is considered the reserve of high-order explosives; however, this case reveals similar injuries from a shotgun (low-order explosive), which has not been reported before to the best of our knowledge.
Assuntos
Traumatismos Cranianos Penetrantes/patologia , Lesão Pulmonar/patologia , Ferimentos por Arma de Fogo/patologia , Adulto , Patologia Legal , Traumatismos Cranianos Penetrantes/etiologia , Humanos , Lacerações/patologia , Lesão Pulmonar/etiologia , Masculino , Ferimentos por Arma de Fogo/complicações , Adulto JovemAssuntos
Simulação por Computador , Seio Maxilar/anatomia & histologia , Seio Maxilar/fisiologia , Modelos Anatômicos , Modelos Teóricos , Ventilação Pulmonar/fisiologia , Convecção , Difusão , Humanos , Radioisótopos de Criptônio , Depuração Mucociliar/fisiologia , Consumo de Oxigênio/fisiologia , CintilografiaRESUMO
The nature of blood aerosols produced in physiological studies of an upright subject expiring small volumes through straws, spitting and mouthing sounds, and a semi-prone subject spitting through a bloody mouth or snorting through a single nasal orifice and by a simplified physical model of the respiratory system were investigated. Each manoeuvre produced many hundreds of droplets of a range of size, the vast majority being less than 1mm diameter. Droplets under 1mm dia. travelled over 1m - much further than could be expected if their flight was ballistic, like that of impact spatter. Respired blood aerosol properties are explained in terms of established mechanics of airflow shear induced aerosol production and the fluid mechanics of exhaled air movement.
Assuntos
Ar , Fenômenos Biofísicos , Manchas de Sangue , Sangue , Expiração , Aceleração , Humanos , Masculino , Modelos Biológicos , Boca , Nariz , Tamanho da Partícula , Postura , FalaRESUMO
BACKGROUND: This study quantifies the time-varying flow rate during inspiration at rest and in sniffing, both predecongestion and postdecongestion. It aims to provide a better understanding of nasal airflow mechanics, for application to the physiological modeling of nasal respiration and to therapeutic drug delivery. METHODS: The temporal profiles of nasal inspiration were measured at high fidelity in 14 healthy individuals using simultaneous bilateral hot-wire anemometry. Peak nasal inspiratory flow (PNIF) rate, acoustic rhinometry (AR), and the sinonasal outcome test (SNOT) provided complementary clinical measurements. The impact of decongestion was also investigated. RESULTS: In the initial phase of inspiration, a rapid rise in flow rate was observed. Flow first exceeded 150 mL/second in either passage within a median time of approximately 120 ms for inspiration at rest and approximately 60 ms in sniffing (â¼20 ms in the fastest sniffs). The mean sustained flow rate attained and the overall period of each measured inspiratory profile were analyzed. AR showed a significant change in nasal volume with decongestion, although these change were not manifest in the temporal profiles of inspiratory flow (barring a weak effect associated with the most vigorous sniffs). CONCLUSION: Novel methods were applied to investigate the temporal profiles of nasal inspiration. Characteristic features of the profile were identified and found to be significantly different between inspiration at rest and sniffing. Decongestion was found to have little effect on the temporal profiles for the flow regimes studied.
Assuntos
Inalação/fisiologia , Descongestionantes Nasais/farmacologia , Ventilação Pulmonar/fisiologia , Adulto , Feminino , Humanos , Imidazóis/farmacologia , Inalação/efeitos dos fármacos , Masculino , Cavidade Nasal/fisiologia , Ventilação Pulmonar/efeitos dos fármacos , Sons Respiratórios/fisiologia , Descanso/fisiologia , Rinometria Acústica , Adulto JovemRESUMO
Effects of acute airway inflammation induced by organic dust inhalation on pulmonary antioxidant status were investigated in healthy horses and horses affected by recurrent airway obstruction. Exposure to organic dust induced acute airway neutrophilia, which was associated with increases in elastase and decreases in ascorbic acid concentrations in bronchoalveolar lavage fluid. However, markers of oxidative stress were unaffected, as was hydrogen peroxide in breath condensate. Decreases in ascorbic acid correlated with increased respiratory resistance (P = .001) when both groups were combined. In conclusion, acute neutrophilic airway inflammation does not result in significant evidence of oxidative stress in horses affected by recurrent airway obstruction.
Assuntos
Antioxidantes/metabolismo , Doenças dos Cavalos/metabolismo , Pulmão/metabolismo , Pneumonia/metabolismo , Pneumonia/veterinária , Doença Aguda , Obstrução das Vias Respiratórias/complicações , Obstrução das Vias Respiratórias/fisiopatologia , Obstrução das Vias Respiratórias/veterinária , Resistência das Vias Respiratórias , Animais , Líquido da Lavagem Broncoalveolar/química , Líquido da Lavagem Broncoalveolar/citologia , Poeira , Feminino , Doenças dos Cavalos/etiologia , Doenças dos Cavalos/fisiopatologia , Cavalos , Elastase de Leucócito/metabolismo , Masculino , Neutrófilos/patologia , Estresse Oxidativo , Pneumonia/etiologia , Pneumonia/fisiopatologiaAssuntos
Obstrução das Vias Respiratórias/veterinária , Antioxidantes/uso terapêutico , Doenças dos Cavalos/tratamento farmacológico , Obstrução das Vias Respiratórias/sangue , Obstrução das Vias Respiratórias/tratamento farmacológico , Animais , Ácido Ascórbico/sangue , Ácido Ascórbico/uso terapêutico , Líquido da Lavagem Broncoalveolar/química , Feminino , Doenças dos Cavalos/etiologia , Cavalos , Peroxidação de Lipídeos/efeitos dos fármacos , Masculino , Tocoferóis/sangue , Tocoferóis/uso terapêuticoRESUMO
INTRODUCTION: Spontaneous electromyographic (EMG) activity in the soleus muscle of the rat varies with the changing gravitational force in parabolic flight, presumably in an appropriate way to resist the load. We investigated how decreased and increased gravitational force affects EMG in human back and arm muscles and to what extent the motor cortex is responsible for any modulation seen. METHODS: Three healthy subjects stood during 10 parabolas consisting of periods (duration 20-25 s) of 1.8 G, then 0 G, and then 1.8 G. EMG recordings were made from right deltoid and left and right erector spinae (ES) muscles and transcranial magnetic stimulation (TMS) was applied to the motor cortex to produce motor evoked potentials (MEPs) in target muscles. RESULTS: In one exemplary subject, EMG levels and MEP areas increased in the left ES and right ES during periods of 0 G, which was less pronounced with the arm abducted. No significant changes were seen in EMG levels or MEP areas during periods of 1.8 G. Pooled data from the three subjects showed a similar pattern, revealing a facilitation of MEP responses in left and right ES muscles in periods of 0 G. DISCUSSION: EMG levels and MEP areas in ES muscles increased during periods of 0 G, suggesting that back muscle activity is "turned on" to stabilize the axial skeleton when the vertical compression forces present on Earth are removed. Further analysis suggested that microgravity produced activation of ES muscles through an increase in corticospinal excitability.
Assuntos
Hipergravidade/efeitos adversos , Tratos Piramidais/fisiologia , Voo Espacial , Ausência de Peso/efeitos adversos , Aceleração , Eletromiografia , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
The relationship between hydrogen peroxide (H2O2) concentration in expired breath condensate (EBC) and cytology of the respiratory tract obtained from tracheal wash (TW) or bronchoalveolar lavage (BAL), and epithelial lining fluid (ELF) antioxidant status is unknown. To examine this we analysed the concentration of H2O2 in breath condensate from healthy horses and horses affected by recurrent airway obstruction (RAO), a condition considered to be an animal model of human asthma. The degree of airway inflammation was determined by assessing TW inflammation as mucus, cell density and neutrophil scores, and by BAL cytology. ELF antioxidant status was determined by measurement of ascorbic acid, dehydroascorbate, reduced and oxidised glutathione, uric acid and alpha-tocopherol concentrations. RAO-affected horses with marked airway inflammation had significantly higher concentrations of breath condensate H2O2 than control horses and RAO-affected horses in the absence of inflammation (2.0 +/- 0.5 micromol/l. 0.4 +/- 0.2 micromol/l and 0.9 +/- 0.2 micromol/l H2O2, respectively; p < 0.0001). The concentration of breath condensate H2O2 was related inversely to the concentration of ascorbic acid in ELF (r = -0.80; p < 0.0001) and correlated positively with TW inflammation score (r = 0.76, p < 0.0001) and BAL neutrophil count (r = 0.80, p < 0.0001). We conclude that the concentration of H2O2 in breath condensate influences the ELF ascorbic acid concentration and provides a non-invasive diagnostic indicator of the severity of neutrophilic airway inflammation.
Assuntos
Obstrução das Vias Respiratórias/diagnóstico , Ácido Ascórbico/análise , Testes Respiratórios/métodos , Modelos Animais de Doenças , Cavalos , Peróxido de Hidrogênio/análise , Obstrução das Vias Respiratórias/patologia , Animais , Ácido Ascórbico/metabolismo , Líquido da Lavagem Broncoalveolar/citologia , Broncoscopia , Contagem de Células , Ácido Desidroascórbico/análise , Ácido Desidroascórbico/metabolismo , Diagnóstico Diferencial , Glutationa/análise , Glutationa/metabolismo , Peróxido de Hidrogênio/metabolismo , Inflamação/diagnóstico , Inflamação/metabolismo , Muco/citologia , Neutrófilos/citologia , Mucosa Respiratória/química , Sistema Respiratório/patologia , EspectrofotometriaRESUMO
Airway compliance is a key factor in understanding lung mechanics and is used as a clinical diagnostic index. Understanding such mechanics in small airways physiologically and clinically is critical. We have determined the "morphometric change" and "localized compliance" of small airways under "near"-physiological conditions; namely, the airways were embedded in parenchyma without dehydration and fixation. Previously, we developed a two-step method to visualize small airways in detail by staining the lung tissue with a radiopaque solution and then visualizing the tissue with a cone-beam microfocal X-ray computed tomography system (Sera et al. J Biomech 36: 1587-1594, 2003). In this study, we used this technique to analyze changes in diameter and length of the same small airways ( approximately 150 microm ID) and then evaluated the localized compliance as a function of airway generation (Z). For smaller (<300-microm-diameter) airways, diameter was 36% larger at end-tidal inspiration and 89% larger at total lung capacity; length was 18% larger at end-tidal inspiration and 43% larger at total lung capacity than at functional residual capacity. Diameter, especially at smaller airways, did not behave linearly with V(1/3) (where V is volume). With increasing lung pressure, diameter changed dramatically at a particular pressure and length changed approximately linearly during inflation and deflation. Percentage of airway volume for smaller airways did not behave linearly with that of lung volume. Smaller airways were generally more compliant than larger airways with increasing Z and exhibited hysteresis in their diameter behavior. Airways at higher Z deformed at a lower pressure than those at lower Z. These results indicated that smaller airways did not behave homogeneously.
Assuntos
Brônquios/fisiologia , Broncografia , Complacência Pulmonar , Radiografia Torácica , Tomografia Computadorizada por Raios X , Animais , Brônquios/anatomia & histologia , Desenho de Equipamento , Expiração , Capacidade Residual Funcional , Imageamento Tridimensional , Técnicas In Vitro , Inalação , Masculino , Modelos Anatômicos , Modelos Biológicos , Ratos , Ratos Wistar , Fatores de Tempo , Tomografia Computadorizada por Raios X/instrumentação , Capacidade Pulmonar TotalRESUMO
Nasal inspiration is important for maintaining the internal milieu of the lung, since ambient air is conditioned to nearly alveolar conditions (body temperature and fully saturated with water vapour) upon reaching the nasopharynx. This literature review of the existing in vivo, in vitro and computational studies on transport phenomena that take place within the human nasal cavity summarizes the current knowledge on air-conditioning characteristics of the human nose.
Assuntos
Ar , Cavidade Nasal/fisiologia , Adulto , Idoso , Regulação da Temperatura Corporal/fisiologia , Humanos , Umidade , Cavidade Nasal/anatomia & histologia , Alvéolos Pulmonares/fisiologia , Ventilação Pulmonar/fisiologia , Doenças Respiratórias/fisiopatologiaRESUMO
OBJECTIVE: To determine the pulmonary epithelial lining fluid (ELF) concentrations and degree of oxidation of ascorbic acid in horses affected by recurrent airway obstruction (RAO) in the presence and absence of neutrophilic airway inflammation. ANIMALS: 6 RAO-affected horses and 8 healthy control horses. PROCEDURE: Nonenzymatic antioxidant concentrations were determined in RBC, plasma, and ELF samples of control horses and RAO-affected horses in the presence and absence of airway inflammation. RESULTS: ELF ascorbic acid concentration was decreased in RAO-affected horses with airway inflammation (median, 0.06 mmol/L; 25th and 75th percentiles, 0.0 and 0.4 mmol/L), compared with RAO-affected horses without airway inflammation (1.0 mmol/L; 0.7 and 1.5 mmol/L) and control horses (2.2 mmol/L; 1.4 and 2.2 mmol/L). Epithelial lining fluid ascorbic acid remained significantly lower in RAO-affected horses without airway inflammation than in control horses. Moreover, the ELF ascorbic acid redox ratio (ie, ratio of the concentrations of dehydroascorbate to total ascorbic acid) was higher in RAO-affected horses with airway inflammation (median, 0.85; 25th and 75th percentiles, 0.25 and 1.00), compared with RAO-affected horses without airway inflammation (0.04; 0.02 and 0.22). The number of neutrophils in bronchoalveolar lavage fluid was inversely related to the ELF ascorbic acid concentration (r = -0.81) and positively correlated with the ascorbic acid redox ratio (r = 0.65). CONCLUSIONS AND CLINICAL RELEVANCE: Neutrophilic inflammation in horses affected by RAO is associated with a reduction in the ELF ascorbic acid pool. Nutritional supplementation with ascorbic acid derivatives in horses affected by RAO is an area for further investigation.
Assuntos
Ácido Ascórbico/análise , Líquido da Lavagem Broncoalveolar/química , Doenças dos Cavalos/fisiopatologia , Pneumopatias Obstrutivas/veterinária , Pulmão/fisiopatologia , Animais , Antioxidantes/análise , Ácido Ascórbico/sangue , Epitélio/fisiopatologia , Doenças dos Cavalos/sangue , Cavalos , Pneumopatias Obstrutivas/sangue , Pneumopatias Obstrutivas/fisiopatologia , Pneumonia/fisiopatologia , Pneumonia/veterináriaRESUMO
Physiological morphometry is a critical factor in the flow dynamics in small airways. In this study, we visualized and analyzed the three-dimensional structure of the small airways without dehydration and fixation. We developed a two-step method to visualize small airways in detail by staining the lung tissue with a radiopaque solution and then visualizing the tissue with a cone-beam microfocal X-ray computed tomographic (CT) system. To verify the applicability of this staining and CT imaging (SCT) method, we used the method to visualize small airways in excised rat lungs. By using the SCT method to obtain continuous CT images, three-dimensional branching and merging bronchi ranging from 500 to 150 microm (the airway generation=8-16) were successfully reconstructed. The morphometry of the small airways (diameter, length, branching angle and gravity angle between the gravity direction and airway vector) was analyzed using the three-dimensional thinning algorithm. The diameter and length exponentially decreased with the airway generation. The asymmetry of the bifurcation decreased with generation and one branching angle decided the other pair branching angle. The SCT method is the first reported method that yields faithful high-resolution images of soft tissue geometry without fixation and the three-dimensional morphometry of small airways is useful for studying the biomechanical dynamics in small airways.
Assuntos
Algoritmos , Brônquios/citologia , Broncografia/métodos , Imageamento Tridimensional/métodos , Intensificação de Imagem Radiográfica/métodos , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Coloração e Rotulagem/métodos , Tomografia Computadorizada por Raios X/métodos , Animais , Meios de Contraste , Pulmão/citologia , Pulmão/diagnóstico por imagem , Masculino , Ratos , Ratos Wistar , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
Vitamin C (ascorbic acid) is a non-enzymatic antioxidant important in protecting the lung against oxidative damage and is decreased in lung lining fluid of horses with airway inflammation. To examine possible therapeutic regimens in a species with ascorbate-synthesising capacity, we studied the effects of oral supplementation of two forms of ascorbic acid, (each equivalent to 20 mg ascorbic acid per kg body weight) on the pulmonary and systemic antioxidant status of six healthy ponies in a 3 x 3 Latin square design. Two weeks supplementation with ascorbyl palmitate significantly increased mean plasma ascorbic acid concentrations compared to control (29 +/- 5 and 18 +/- 7 micromol/l, respectively; p < 0.05). Calcium ascorbyl-2-monophosphate, a more stable form of ascorbic acid, also increased mean plasma ascorbic acid concentrations, but not significantly (23 +/- 1 micromol/l; p = 0.07). The concentration of ascorbic acid in bronchoalveolar lavage fluid increased in five out of six ponies following supplementation with either ascorbyl palmitate or calcium ascorbyl-2-monophosphate compared with control (30 +/- 10, 25 +/- 4 and 18 +/- 8 micromol/l, respectively; p < 0.01). Neither supplement altered the concentration of glutathione, uric acid or alpha-tocopherol in plasma or bronchoalveolar lavage fluid. In conclusion, the concentration of lung lining fluid ascorbic acid is increased following ascorbic acid supplementation (20 mg/kg body weight) in an ascorbate-synthesising species.