Decreased Pressure Gradient Research Articles

Pulmonary Valve Pressure Gradient in Pulmonary Stenosis: Before and After Balloon Valvuloplasty

Pulmonary valve stenosis is common among other congenital heart diseases. The need to treat the stenosis was based on the presence of symptomatic signs. Balloon valvuloplasty is commonly used because it is less invasive than surgery. However, the study about decreased pressure gradient in pulmonary stenosis after balloon valvuloplasty was still limited. Thus, this article review aimed to see how much the reduction of pressure gradient after balloon valvuloplasty in pulmonary stenosis. The search engine used in this study was PubMed, then the articles were selected according to PICO (population, intervention, comparison, and outcomes). Only articles containing data about patients with pulmonary stenosis who underwent balloon valvuloplasty and comparing before and after mean pressure gradients to see the outcomes after balloon valvuloplasty was included in this literature review. The mean of pressure gradient from all the data before treatment was grouped into <50mmHg, 50 - 80 mmHg, >80 mmHg, then we combined the mean, and the result was 42.28 mmHg 77.43 mmHg 92.62 mmHg, respectively. The mean after treatment was also grouped into <50mmHg, 50 – 80 mmHg, >80 mmHg, and the result were 12.96mmHg 26.78mmHg 30.65mmHg, respectively. The reduction in gradient pressure was more than 50% in all groups. Thus, balloon valvuloplasty is an efficient treatment for pulmonary stenosis.

Performance analysis of the separator with inner channels by experiment and CFD-POST

ABSTRACT The separator with inner channels is designed to solve the re-entrainment phenomenon of particles, improving the separation efficiency. Firstly, experiments are established to compare the separation efficiency and pressure drop between ordinary separators and ones with inner channels. Secondly, the Reynolds Stress model and the Euler–Euler model are applied to simulate the turbulence and particle flow, respectively. Lastly, the Population Balance model (PBM) is used to define different distributions of particle diameter by initial moments. The research results demonstrate that the inner channels can improve separation efficiency significantly because they can restrain the re-entrainment phenomenon. The separation efficiency of the design and the conventional ones is 97% and 90%, respectively, but the pressure drop increases by 39 Pa in this structure. Simultaneously, this structure has a lower tangential velocity compared with the separator without inner channels, reducing particle collisions with the wall. Radial pressure differences are also declined in the structures with inner channels, leading to a decreased pressure gradient force. Furthermore, the sixth moment has a larger median particle size, while the particle size distribution at the outlet of the separator is similar to that at the inlet via the PBM. And the maximum separation efficiency of the design and ordinary ones is 99% and 80%, respectively. The characteristics listed above can help with efficient separator design.

Outcomes of Arch Reintervention for Recurrent Coarctation in Young Children.

To evaluate the outcomes of reintervention for postrepair recoarctation in young children. Between January 2011 and December 2020, all consecutive patients aged ≤3 years who were treated for postrepair recoarctation were included. Recoarctations were classified into two morphological types by three-dimensional imaging. Two methods, namely, surgical repair and balloon angioplasty (BA), were used to treat recoarctation. This study included 50 patients with a median age of 10.5 months (range, 2.0-36.0 months) and a mean weight of 9.3 ± 3.1 kg. Hypoplastic recoarctation occurred most frequently in patients who had undergone patch aortoplasty at initial repair (p = 0.001). No hospital mortality occurred, and all patients achieved an increased diameter (p < 0.001) and a decreased pressure gradient (p < 0.001) at the recoarctation site immediately after reintervention. The median follow-up time after reintervention was 3.5 years (range, 16.0 days-9.6 years). Late mortality occurred in four patients (8.0%): two in the surgical group and two in the BA group (chi-square test= 0.414, p = 0.520). There was no difference in arch reobstruction after reintervention between the surgical and BA groups (chi-square test = 1.383, p = 0.240). Recoarctation with a hypoplastic morphology was the leading risk factor for arch reobstruction after reintervention (hazard ratio, 6.552; 95% confidence interval, 2.045-20.992; p = 0.002). Reintervention for recoarctation has favorable early outcomes in young children. However, late mortality is not rare, and arch reobstruction is common during close follow-up. For young children, recoarctation with hypoplastic morphology is the leading risk factor for reobstruction, while the choice of reintervention method exerts little effect on the outcomes of arch reintervention.

Relationship between decreased pressure gradient and reservoir filling degree of paleogene in Bonan Sag

Overpressure plays an important role in oil and gas migration. Decreased pressure gradient, as a characterization of overpressure, refers to the variation range of pressure per unit distance and has great significance for studying the dynamic composition and mechanism of oil and gas migration in the process of hydrocarbon migration. To quantitatively identify the relation between overpressure and hydrocarbon accumulation, this study uses the Es3 Formation in Bonan Sag as an example. The pressure distribution characteristics, the plane decreased pressure gradient characteristics, and their relationship with reservoir filling degree are analyzed using the measured pressure and predicted pressure, combined with the calculation of decreased pressure gradient and reservoir filling degree. Results show that the pressure coefficient of the Es3 Formation in Bonan Sag reaches up to 1.85, the decreased pressure gradient on the plane exhibits heterogeneity, and the decreased pressure gradient of the deep sub-sag belt is the highest, reaching a maximum of 12.1 MPa/km, followed by steep slope and steep fault belts. The gentle slope belt has the lowest decreased pressure gradient of less than 4.4 MPa/km. The corresponding relationship between decreased pressure gradient and reservoir filling degree is different in the four structure belts. The deep sub-sag belt is bounded by the decreased pressure gradient of 9.7 MPa/km. When the decreased pressure gradient is less than 9.7 MPa/km, the reservoir filling degree increases with an increase in the decreased pressure gradient. When the decreased pressure gradient is greater than 9.7 MPa/km, the reservoir filling degree decreases with an increase in the decreased pressure gradient. The corresponding relationship in the steep fault belt is opposite that of the deep sub-sag belt. When the decreased pressure gradient is greater than 4 MPa/km, the reservoir filling degree decreases with a decrease in the decreased pressure gradient, whereas the relationship between the decreased pressure gradient and the reservoir filling degree is weak in the gentle slope belt.

Investigation of causes of layer inversion and prediction of inversion velocity in liquid fluidizations of binary particle mixtures

Liquid fluidization plays an important role in mineral processing such as solid classifiers and biological reactors. When particle properties differ in size, density or shape, segregation can occur. Typically, a segregation phenomenon so-called layer inversion in two-phase solid-liquid fluidization of binary mixtures has been reported in the literature. At low liquid velocities, the two species form distinct layers with the denser smaller particles at the bottom and the lighter larger particles at the top. At high liquid velocities, however, the two layers are inverted with smaller particles being at the top while larger ones at the bottom. In this work, glass beads (193 μm) and activated carbon (778 μm) are used in the simulation as those in Jean and Fan (1986), and the layer inversion is successfully reproduced by CFD-DEM. The underlying segregation mechanism is analyzed in terms of particle-fluid interaction forces. The results reveal that the layer inversion is caused by the relative change of particle-fluid interaction forces on particles. For large particles, the reduction of the pressure gradient force cannot be compensated by the increased drag force, resulting in the downward flow. Meanwhile, small particles tend to move upward because the increased drag force exceeds the decreased pressure gradient force. In addition, the effects of particle and liquid properties on layer inversion are examined, and different drag force models in predicting the layer inversion are also assessed. It indicates that Rong et al.'s drag model represents the layer inversion with the best accuracy. Finally, a model based on the force balance criterion is proposed to predict the inversion velocity showing a better accuracy.

Morphological and Hemodynamic Effectiveness of Stenting for Pulmonary Artery Stenosis - Subanalysis of JPIC Stent Survey.

Percutaneous stenting for branch pulmonary artery stenosis is an established interventional choice in congenital heart disease. The apparent morphologic change in the vessel diameter often differs from the hemodynamic result. We performed a subanalysis of the data from the Japanese Society of Pediatric Interventional Cardiology (JPIC) stent survey. The factors that may have contributed to morphologic effectiveness included reference vessel diameter (RVD), minimum lumen diameter (MLD) and percent diameter stenosis (%DS) and the relation between morphologic and hemodynamic effectiveness was evaluated in 206 lesions treated with stenting. We defined a "50% increase in MLD" as "morphologically effective", while "achievement of either a reduced pressure gradient greater than 50% or an increase of perfusion ratio to the affected side to the contralateral side greater than 20%" as "hemodynamically effective". Morphologic effectiveness was achieved in 84% of patients. Before stenting, %DS was significantly larger, while RVD was smaller in the "effective" group than in the "non-effective" group. The cutoff value for effective stenting was 51% for %DS and 14.7 mm for RVD before stenting. Hemodynamic effectiveness was obtained more often in the "morphologic effective" group. RVD and %DS were the 2 main contributors to acute morphologic effectiveness. There was a significant relationship between "morphologic effectiveness" and "hemodynamic effectiveness", judging from increased perfusion of the affected lung and/or decreased pressure gradient. (Circ J 2016; 80: 1852-1856).

Solar cycle modulation of the ENSO impact on the winter climate of East Asia

This study examines how the East Asian winter climate response to the El Niño‐Southern Oscillation (ENSO) varies with the 11‐year solar cycle. The results indicate that the ENSO and East Asian climate relationship is robust and significant during winters with low solar (LS) activity, with evident warming in the lower troposphere over East Asia, which can be closely linked to the decreased pressure gradient between the cold Eurasian continent and the warm Pacific. Moreover, during the LS and El Niño winters, there is a typical rainfall response in Southeast Asia, with wet conditions over South China and dry conditions over the Philippines, Borneo, Celebes, and Sulawesi, which can be explained by the anticyclone over the western North Pacific (WNP). However, during high solar activity winters, both the surface temperature and rainfall anomalies are much less closely associated with the ENSO. The possible mechanism for this solar modulation of the ENSO‐related East Asian climate anomalies may be the change in the tropospheric circulation with the ENSO in both tropical and extratropical regions. Particularly, in the LS cases, an anomalous WNP anticyclone is intensified and a noticeable cyclone occupies northern Northeast Asia, resulting from the changing location and strength of the large‐scale Walker circulation induced by the more pronounced sea surface temperature anomalies associated with the ENSO. Further investigation with long historic data confirms that the relationship between the ENSO and the East Asian winter climate anomalies depends on the phases of 11 year solar cycle, with enhanced East Asian climate variation during the LS winters.

Apico-Aortic Conduit for Aortic Stenosis in a Patient with Chronic Thoracic Wall Infection

We report a case of an apico-aortic bioprothesis-valved conduit for a 70-year-old-woman with symptomatic, severe aortic stenosis and severe calcification of the ascending aorta. She had a history of mastectomy and radiation therapy for breast cancer and was suffering from radiodermatitis and chronic thoracic wall infection. Transthoracic echocardiography showed severe aortic valve stenosis with heavy calcification and high aortic valve pressure gradients. In patients with a chronically infected thoracic wall, median sternotomy is considered to be a high risk procedure, resulting in postoperative mediastiniti; therefore, we applied a technique in which we used an apico-aortic conduit via posterolateral thoracotomy. We underwent apico-aortic bypass with a hand-made composite graft: 19-mm bioprosthetic valve and a 22-mm woven polyester vascular graft. The surgical intervention successfully decreased pressure gradient across the aortic valve, also separating an incision from chronic infection allowed us to avoid postoperative mediastinitis. The patient had remained in good condition for 15 months without developing any complications.

Computational Fluid Dynamic Study on Obstructive Sleep Apnea Syndrome Treated With Maxillomandibular Advancement

Maxillomandibular advancement is one of the treatments available for obstructive sleep apnea. The influence of this surgery on the upper airway and its mechanism are not fully understood. The present research simulates the flow fields of narrowed upper airways of 2 patients with obstructive sleep apnea treated with maxillomandibular advancement. The geometry of the upper airway was reconstructed from computed tomographic images taken before and after surgery. The consequent three-dimensional surface model was rendered for measurement and computational fluid dynamics simulation. Patients showed clinical improvement 6 months after surgery. The cross-sectional area of the narrowest part of the upper airway was increased in all dimensions. The simulated results showed a less constricted upper airway, with less velocity change and a decreased pressure gradient across the whole conduit during passage of air. Less breathing effort is therefore expected to achieve equivalent ventilation with the postoperative airway. This study demonstrates the possibility of computational fluid dynamics in providing information for understanding the pathogenesis of OSA and the effects of its treatment.

Percutaneous balloon dilation angioplasty of pulmonary artery branch stenosis.

Congenital or acquired branch pulmonary artery stenosis can produce significant right ventricular hypertension and complicate the management of patients with tetralogy of Fallot. Repair is difficult using conventional surgical techniques. Balloon dilation angioplasty may be beneficial to some patients with these lesions. The technique currently used at the University of Minnesota is described. Results indicate that half of attempted dilations are successful with increased diameter of the narrowed areas, decreased pressure gradient, and improved pulmonary blood flow to the involved lung. Failure may be caused by technical limitations (28%) or lesions that are not dilatable with current equipment (22%). Undilatable lesions are more common in children over 2 years of age, in isolated pulmonary artery stenosis, and with associated surgical shunts. Complications are uncommon.