ABSTRACT
Mechanical ventilation is an importmant life-sustaining treatment for patients with acute respiratory distress syndrome. Its clinical outcomes depend on patients' characteristics of lung recruitment. Estimation of lung recruitment characteristics is valuable for the determination of ventilatory maneurvers and ventilator parameters. There is no easily-used, bedside method to assess lung recruitment characteristics. The present paper proposed a method to estimate lung recruitment characteristics from the static pressure-volume curve of lungs. The method was evaluated by comparing with published experimental data. Results of lung recruitment derived from the presented method were in high agreement with the published data, suggesting that the proposed method is capable to estimate lung recruitment characteristics. Since some advanced ventilators are capable to measure the static pressure-volume curve automatedly, the presented method is potential to be used at bedside, and it is helpful for clinicians to individualize ventilatory manuevers and the correpsonding ventilator parameters.
Subject(s)
Humans , Lung , Positive-Pressure Respiration , Respiration, Artificial , Respiratory Distress Syndrome, Newborn , Ventilators, MechanicalABSTRACT
Objective To study the method of estimating noninvasive dynamic respiratory mechanics parameters for patients with chronic obstructive pulmonary disease (COPD). Methods By simplifying the human respiratory system into a first order single compartment model and setting constraints based on optimization method, the respiratory system resistance and compliance of COPD patients were estimated. Results By using the model and setting the constraint conditions in the simulation experiment, the respiratory system resistance and compliance of COPD patients with spontaneous breathing could be estimated, and the results were relatively accurate (within 5% error). The estimated result could be obtained by data of one respiratory cycle within three respiratory cycles, which could meet the requirements of dynamic monitoring data. Conclusions Based on optimization method, the noninvasive dynamic evaluation on respiratory resistance and compliance of COPD patients were carried out in simulation experiments and proved to be feasible for further clinical trials. The research findings could help doctors to monitor the resistance and compliance changes of COPD patients in real time after clinical trial, and provided references for diagnosis and treatment of COPD.
ABSTRACT
Objective To study the method of estimating noninvasive dynamic respiratory mechanics parameters for patients with chronic obstructive pulmonary disease (COPD). Methods By simplifying the human respiratory system into a first order single compartment model and setting constraints based on optimization method, the respiratory system resistance and compliance of COPD patients were estimated. Results By using the model and setting the constraint conditions in the simulation experiment, the respiratory system resistance and compliance of COPD patients with spontaneous breathing could be estimated, and the results were relatively accurate (within 5% error). The estimated result could be obtained by data of one respiratory cycle within three respiratory cycles, which could meet the requirements of dynamic monitoring data. Conclusions Based on optimization method, the noninvasive dynamic evaluation on respiratory resistance and compliance of COPD patients were carried out in simulation experiments and proved to be feasible for further clinical trials. The research findings could help doctors to monitor the resistance and compliance changes of COPD patients in real time after clinical trial, and provided references for diagnosis and treatment of COPD.
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One-compartment lumped-parameter models of respiratory mechanics, representing the airflow resistance of the tracheobronchial tree with a linear or nonlinear resistor, are not able to describe the mechanical property of airways in different generations. Therefore, based on the anatomic structure of tracheobronchial tree and the mechanical property of airways in each generation, this study classified the human airways into three segments: the upper airway segment, the collapsible airway segment, and the small airway segment. Finally, a nonlinear, multi-compartment lumped-parameter model of respiratory mechanics with three airway segments was established. With the respiratory muscle effort as driving pressure, the model was used to simulate the tidal breathing of healthy adults. The results were consistent with the physiological data and the previously published results, suggesting that this model could be used for pathophysiological research of respiratory system.
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Objective To study the changes of nitric oxide (NO) concentration in arterial-capillary-venous vessels and the dynamic regulation mechanism of NO on the vessels during ventilation changes. Method The pulmonary vascular network model was established by using the COMSOL Multiphysics software, the dynamic regulation of NO on blood vessels was introduced, the flow-multiphysics coupling simulation was conducted to explore the effect of oxygen and blood flow on NO concentration and its distribution in pulmonary vascular network, and the dynamic regulation of NO on pulmonary vascular function in the case of ventilation lacking. Results Oxygen concentration and blood flow would jointly affect the NO distribution in the pulmonary vascular network. When lung ventilation was insufficient, the amount of oxygen entering the pulmonary capillaries decreased, and the NO concentration in pulmonary vein walls under static conditions was significantly reduced. The reduction of NO concentration under dynamic conditions led to vasoconstriction and decrease of blood vessel radius, resulting a dynamic compensation. Regulation of vascular tension regulation coefficient α would directly affect the regulation of NO. When α worked within a certain range, a higher value of α meant a larger change in vascular radius and a smaller change in NO concentration, and its effective value was greater than 1. Conclusions The research findings revealed the change of NO concentration in arterial-capillary-venous vessels due to the change of ventilation as well as the dynamic regulation mechanism of NO in blood vessels, and predicted the effective value range of α，thus providing theoretical basis for further research on the mechanism of blood flow, ventilation perfusion ratio affected by vasoconstriction and vascular resistance changes due to ventilation insufficiency.
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Objective:To anslysis the hemodynamic states of vertebrobasilar dolichoectasia based on computational fluid dynamics technique.Methods:The original DICOM format image data from a patient with vertebrobasilar dolichoectasia (VBD), were imported by the Mimics software directly,and the 3D Objects were constructed.The simulation of model was made with Ansys software, the hemodynamic pa-rameters such as streamlines, wall shear stress( WSS) and wall pressure were described.Results:There was stable laminar flow in proximal basilar artery and was no blood flow mixed by bilateral vertebral arter-y.However, Spiral flows were appeared in distal tortuous basilar artery.The low WSS regions in the ver-tebra-basilar junction section and inferior segment of basilar artery were coincide with the high wall pres-sure regions.It could be speculated the initial growth regions might be located in the vertebra-basilar junction section and inferior segment of basilar artery.Local regions with low WSS and high wall pressure might be associated with the occurrence and development of VBD.Conclusion: CFD numerical simula-tion maybe can provide a theoretical basis for the role of hemodynamic factors in occurrence and develop-ment of VBD.
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Objective:To study the morphology of middle cerebral artery ( MCA ) M1 segment .Me-thods:We selected the MRA data of 794 MCA (400 of the left side and 394 of the right side ) from Ja-nuary 1, 2011 to June 30, 2011 consecutively and analyzed the morphology of the MCA M 1 segment in axial, anteroposterior and lateral view , measured the length of the M1 segment, and analyzed the simila-rity of the left and right side M1 segment morphology .Results:In axial, anteroposterior and lateral view , the MCA M1 segment showed C-shape >L-shape >S-shape .In axial view , it was about 373 ( 47%) M1 segment performance for the C-shape, of which 340 (42.8%) M1 segments showed bowing to the dorsal side, only 33 (4.2%) M1 segments showed bowing to the ventral side .In anteroposterior view, it was about 322 (40.6%) M1 segments of the performance of the C-shape, of which 262(33.0%) M1 segments showed a bowing to the superior , 60 (7.6%) showed bowing to the inferior .The similarity of the left and right MCA M1 segments was 27.2% (114/419) in axial view and 42.7% (179/419) in anteroposterior view.It was more similar in anteroposterior view than in axial view .Along with the increase of age, in the axial view, L-shape converted to C-shape very obviously, but only mildly elevated in S-shape .In anteroposterior view , the L-shape converted to the C-shape or S-shape along with the increase of age.Conclusion:The different morphology of MCA M1 segment in axial and anteroposterior view may be involved in the development of intracranial atherosclerosis .
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Positron emission tomography(PET) plays an important role in the research of substance distribution in Human body. The distribution of substance in whole body is carried out by the transport via circulation system and exchange between blood and tissue which occurs in microvascular. Both the research of PET and of microvascular are focused on the transport and exchange of substance in human body. So it should be meaningful to apply PET image to the research of microvascular, and to use the microvascular theory to improve on the analysis of PET image. In this article, some research in this domain are introduced, and foreground is reviewed.