The Experts below are selected from a list of 14667 Experts worldwide ranked by ideXlab platform

Alexis A Thompson - One of the best experts on this subject based on the ideXlab platform.

  • risk factors and mortality associated with an elevated tricuspid regurgitant Jet Velocity measured by doppler echocardiography in thalassemia a thalassemia clinical research network report
    Blood, 2011
    Co-Authors: Claudia R Morris, Alexis A Thompson, Nancy Sweeters, Felicia Trachtenberg, John C Wood, Charles T Quinn, Janet L Kwiatkowski, Patricia J Giardina, Jeanne Boudreaux, Nancy F Olivieri
    Abstract:

    An elevated tricuspid regurgitant Jet Velocity (TRV) is associated with hemolysis and early mortality in sickle cell disease, yet risk factors, clinical parameters, and mortality associated with this biomarker in thalassemia are poorly defined. This report summarizes the prevalence of an elevated TRV in 325 patients screened by Doppler echocardiography in the Thalassemia Clinical Research Network. A documented TRV was reported in 148 of 325 (46%) of patients. Average age was 25.9 years (range, 5-56 years) and 97% were transfusion-dependent. Mean TRV was 2.3 ± 0.4 m/s (range, 0.2-3.5 m/s). An abnormal TRV ≥ 2.5 m/s was identified in 49 of 148 (33%) of patients with a documented TRV, 5% (8/148), with a TRV ≥ 3.0 m/s, suggesting significant PH risk. Older age was strongly associated with a high TRV; however, 16% of children had a TRV ≥ 2.5 m/s. A history of splenectomy, hepatitis C, smoking, or high white blood cell count was associated with TRV elevation. In summary, an elevated TRV is noted in one-third of transfusion-dependent thalassemia patients with a documented value and develops in both children and adults. Age, splenectomy, hepatitis C, and smoking are significant univariate risk factors, with splenectomy surfacing as the dominant risk factor over time. Mortality was low in this cohort. Prospective longitudinal studies are needed. This study is registered at as [NCT00661804][1]. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT00661804&atom=%2Fbloodjournal%2F118%2F14%2F3794.atom

  • Reproducibility of tricuspid regurgitant Jet Velocity measurements in children and young adults with sickle cell disease undergoing screening for pulmonary hypertension
    American Journal of Hematology, 2010
    Co-Authors: Robert I Liem, Luciana T Young, Stephanie A. Pelligra, Richard J. Labotka, Alexis A Thompson
    Abstract:

    The reproducibility of tricuspid regurgitant Jet Velocity (TRJV) measurements by Doppler echocardiography has not been subjected to systematic evaluation among individuals with sickle cell disease (SCD) undergoing screening for pulmonary hypertension. We examined sources of disagreement associated with peak TRJV in children and young adults with SCD. Peak TRJV was independently measured and interpreted a week apart by separate sonographers and readers, respectively, in 30 subjects (mean age, 15.8 ± 3.3 years) who provided 120 observations. We assessed intra-/inter-reader, intra-/inter-sonographer, sonographer-reader, and within subject agreement using Intraclass Correlation Coefficient (ICC) and Cohen's kappa (κ). Agreement was examined graphically using Bland-Altman plots. Although sonographers could estimate and measure peak TRJV in all subjects, readers designated tricuspid regurgitation nonquantifiable in 10–17% of their final interpretations. Intra-reader agreement was highest (ICC = 0.93 [95% CI 0.86, 0.97], P = 0.0001) and within subject agreement lowest (ICC = 0.36 [95% CI 0.02, 0.64], P = 0.021) for single TRJV measurements. Similarly, intra-reader agreement was highest (κ = 0.74 [95% CI 0.53, 0.95], P = 0.0001) and within subject lowest (κ = 0.14 [95% CI −0.17, 0.46], P = 0.38) when sonographers and readers categorized TRJV measurements. On Bland-Altman plots, absolute differences in observations increased with higher mean TRJV readings for intra-/inter-reader agreement. Peak TRJV measurements in individual children and young adults with SCD are affected by several sources of disagreement, underscoring the need for methodological improvements that ensure reproducibility of this screening modality for making clinical decisions in this population. Am. J. Hematol., 2010. © 2010 Wiley-Liss, Inc.

  • Reliability of Tricuspid Regurgitant Jet Velocity Measurements in Children and Young Adults with Sickle Cell Disease.
    Blood, 2009
    Co-Authors: Robert I Liem, Luciana T Young, Stephanie A. Pelligra, Richard J. Labotka, Amy D. Shah, Alexis A Thompson
    Abstract:

    Abstract 2581 Poster Board II-558 Tricuspid regurgitant Jet Velocity (TRJV) measurements are used commonly for estimating pulmonary artery pressures among individuals with sickle cell disease (SCD) undergoing screening for pulmonary hypertension, defined by TRJV ≥ 2.5 m/sec. Measurements, however, may be prone to variability and have not been subjected to reliability testing in this population. The objective of our study was to examine reliability as well as potential sources of variability associated with TRJV measurements in a cohort of children and young adults with SCD. Methods We evaluated TRJV at steady state in a convenience sample of 30 subjects (53% male) with SCD (SS n=25, SC n=1, S-Beta0 thalassemia n=4) during 2 separate visits 1 week apart. In a blinded fashion, peak TRJV was independently measured by 2 experienced sonographers and officially interpreted by 2 readers who were attending cardiologists at standard time points in the protocol that permitted assessment of reliability and agreement. We calculated within subject variability as well as intra-/inter-sonographer and reader reliability in this analysis using Intraclass Correlation Coefficient (ICC) and Cohen9s kappa to assess TRJV as a continuous and categorical variable, respectively. Agreement was also examined graphically using Bland-Altman plots. Results Sonographers were able to measure TRJV in all subjects (mean age, 15.8±3.3 years, range 10 to 22). Readers, however, designated tricuspid regurgitation unquantifiable in 13% of their final interpretations, most commonly due to an inadequate Doppler window. We found that intra-reader reliability was highest (ICC=0.93 [95% CI 0.86, 0.97], p Conclusions In summary, quantification of tricuspid regurgitation as well as classification of TRJV values in children and young adults with SCD are affected by several potential sources of variability, including intra-/inter-sonographer and reader differences in measurement and interpretation. Despite using a single sonographer for its determination, within subject reliability in our analysis was especially poor, which may in part reflect sonographer ability to obtain Doppler windows adequate for accurate quantification of tricuspid regurgitation. Our findings underscore the need for methodological improvements that ensure the reliability of measurements used to diagnose TRJV elevation in this population. Multi-institutional reliability testing may also be required to establish the degree of variability that should be considered acceptable in clinical trials involving individuals with SCD and TRJV elevation. Disclosures: No relevant conflicts of interest to declare.

  • tricuspid regurgitant Jet Velocity elevation and its relationship to lung function in pediatric sickle cell disease
    Pediatric Pulmonology, 2009
    Co-Authors: Robert I Liem, Luciana T Young, Mary A Nevin, Adrienne Prestridge, Alexis A Thompson
    Abstract:

    Concerns about the morbidity and mortality associated with tricuspid regurgitant Jet Velocity (TRJV) elevation, which may indicate pulmonary hypertension (PHT), in adults with sickle cell disease (SCD) have prompted growing interest in screening the pediatric sickle cell population. The goals of our study were to estimate the prevalence of TRJV elevation and determine its relationship to pulmonary function in children and young adults with SCD at baseline. Seventy-eight subjects (10–24 years old) with SCD underwent prospective screening by Doppler echocardiogram (ECHO), complete lung function evaluation, and laboratory testing as part of standard care at steady state. Tricuspid regurgitation was quantifiable in 68/78 (87%) subjects and peak TRJV was ≥2.5 m/sec in 26/78 (33.3%) evaluated. The frequency of obstruction, restriction, or abnormal gas exchange found on lung function evaluation was not significantly different in subjects with and without TRJV elevation. However, significant inverse correlations were observed between TRJV and both % predicted forced vital capacity (FVC) (r = −0.29, P = 0.022) and oxygen saturation (r = −0.26, P = 0.036). When compared to subjects without TRJV elevation, subjects with TRJV elevation had significantly lower % predicted forced expiratory volume in 1 sec (FEV1) (78.9 ± 14.4 vs. 86.6 ± 13.0%, P = 0.023), FVC (82.8 ± 14.1 vs. 90.7 ± 12.9%, P = 0.017), and oxygen saturation (95.8 ± 3.2 vs. 97.5 ± 2.4%, P = 0.016). We found that the combination of low hemoglobin and low % predicted FVC best predicted TRJV elevation (χ2 = 17.05, P = 0.001) in our cohort, correctly identifying 70% of cases and resulting in positive and negative predictive values of 60 and 74%, respectively. We conclude that in this young population with SCD, TRJV elevation that is not significantly associated with abnormal lung function is common at baseline. Pediatr Pulmonol. 2009; 44:281–289. © 2009 Wiley-Liss, Inc.

  • tricuspid regurgitant Jet Velocity is associated with hemolysis in children and young adults with sickle cell disease evaluated for pulmonary hypertension
    Haematologica, 2007
    Co-Authors: Robert I Liem, Luciana T Young, Alexis A Thompson
    Abstract:

    Tricuspid regurgitant Jet Velocity (TRJV) ≥ 2.5 m/sec. on echocardiography is a surrogate marker for pulmonary hypertension (PHT) in adults with sickle cell disease (SCD). We prospectively examined the relationship between TRJV and laboratory markers of hemolysis in 51 children and young adults with SCD at baseline. We found significant correlations between TRJV and lactate dehydrogenase (LDH), hemoglobin (Hb), reticulocyte count (retic) and aspartate aminotransferase (AST). LDH, retic and AST were significantly higher and Hb was lower in subjects with TRJV ≥ 2.5 m/sec. We conclude that hemolysis significantly contributes to TRJV elevation in children and young adults with SCD.

Robert I Liem - One of the best experts on this subject based on the ideXlab platform.

  • Reproducibility of tricuspid regurgitant Jet Velocity measurements in children and young adults with sickle cell disease undergoing screening for pulmonary hypertension
    American Journal of Hematology, 2010
    Co-Authors: Robert I Liem, Luciana T Young, Stephanie A. Pelligra, Richard J. Labotka, Alexis A Thompson
    Abstract:

    The reproducibility of tricuspid regurgitant Jet Velocity (TRJV) measurements by Doppler echocardiography has not been subjected to systematic evaluation among individuals with sickle cell disease (SCD) undergoing screening for pulmonary hypertension. We examined sources of disagreement associated with peak TRJV in children and young adults with SCD. Peak TRJV was independently measured and interpreted a week apart by separate sonographers and readers, respectively, in 30 subjects (mean age, 15.8 ± 3.3 years) who provided 120 observations. We assessed intra-/inter-reader, intra-/inter-sonographer, sonographer-reader, and within subject agreement using Intraclass Correlation Coefficient (ICC) and Cohen's kappa (κ). Agreement was examined graphically using Bland-Altman plots. Although sonographers could estimate and measure peak TRJV in all subjects, readers designated tricuspid regurgitation nonquantifiable in 10–17% of their final interpretations. Intra-reader agreement was highest (ICC = 0.93 [95% CI 0.86, 0.97], P = 0.0001) and within subject agreement lowest (ICC = 0.36 [95% CI 0.02, 0.64], P = 0.021) for single TRJV measurements. Similarly, intra-reader agreement was highest (κ = 0.74 [95% CI 0.53, 0.95], P = 0.0001) and within subject lowest (κ = 0.14 [95% CI −0.17, 0.46], P = 0.38) when sonographers and readers categorized TRJV measurements. On Bland-Altman plots, absolute differences in observations increased with higher mean TRJV readings for intra-/inter-reader agreement. Peak TRJV measurements in individual children and young adults with SCD are affected by several sources of disagreement, underscoring the need for methodological improvements that ensure reproducibility of this screening modality for making clinical decisions in this population. Am. J. Hematol., 2010. © 2010 Wiley-Liss, Inc.

  • Reliability of Tricuspid Regurgitant Jet Velocity Measurements in Children and Young Adults with Sickle Cell Disease.
    Blood, 2009
    Co-Authors: Robert I Liem, Luciana T Young, Stephanie A. Pelligra, Richard J. Labotka, Amy D. Shah, Alexis A Thompson
    Abstract:

    Abstract 2581 Poster Board II-558 Tricuspid regurgitant Jet Velocity (TRJV) measurements are used commonly for estimating pulmonary artery pressures among individuals with sickle cell disease (SCD) undergoing screening for pulmonary hypertension, defined by TRJV ≥ 2.5 m/sec. Measurements, however, may be prone to variability and have not been subjected to reliability testing in this population. The objective of our study was to examine reliability as well as potential sources of variability associated with TRJV measurements in a cohort of children and young adults with SCD. Methods We evaluated TRJV at steady state in a convenience sample of 30 subjects (53% male) with SCD (SS n=25, SC n=1, S-Beta0 thalassemia n=4) during 2 separate visits 1 week apart. In a blinded fashion, peak TRJV was independently measured by 2 experienced sonographers and officially interpreted by 2 readers who were attending cardiologists at standard time points in the protocol that permitted assessment of reliability and agreement. We calculated within subject variability as well as intra-/inter-sonographer and reader reliability in this analysis using Intraclass Correlation Coefficient (ICC) and Cohen9s kappa to assess TRJV as a continuous and categorical variable, respectively. Agreement was also examined graphically using Bland-Altman plots. Results Sonographers were able to measure TRJV in all subjects (mean age, 15.8±3.3 years, range 10 to 22). Readers, however, designated tricuspid regurgitation unquantifiable in 13% of their final interpretations, most commonly due to an inadequate Doppler window. We found that intra-reader reliability was highest (ICC=0.93 [95% CI 0.86, 0.97], p Conclusions In summary, quantification of tricuspid regurgitation as well as classification of TRJV values in children and young adults with SCD are affected by several potential sources of variability, including intra-/inter-sonographer and reader differences in measurement and interpretation. Despite using a single sonographer for its determination, within subject reliability in our analysis was especially poor, which may in part reflect sonographer ability to obtain Doppler windows adequate for accurate quantification of tricuspid regurgitation. Our findings underscore the need for methodological improvements that ensure the reliability of measurements used to diagnose TRJV elevation in this population. Multi-institutional reliability testing may also be required to establish the degree of variability that should be considered acceptable in clinical trials involving individuals with SCD and TRJV elevation. Disclosures: No relevant conflicts of interest to declare.

  • tricuspid regurgitant Jet Velocity elevation and its relationship to lung function in pediatric sickle cell disease
    Pediatric Pulmonology, 2009
    Co-Authors: Robert I Liem, Luciana T Young, Mary A Nevin, Adrienne Prestridge, Alexis A Thompson
    Abstract:

    Concerns about the morbidity and mortality associated with tricuspid regurgitant Jet Velocity (TRJV) elevation, which may indicate pulmonary hypertension (PHT), in adults with sickle cell disease (SCD) have prompted growing interest in screening the pediatric sickle cell population. The goals of our study were to estimate the prevalence of TRJV elevation and determine its relationship to pulmonary function in children and young adults with SCD at baseline. Seventy-eight subjects (10–24 years old) with SCD underwent prospective screening by Doppler echocardiogram (ECHO), complete lung function evaluation, and laboratory testing as part of standard care at steady state. Tricuspid regurgitation was quantifiable in 68/78 (87%) subjects and peak TRJV was ≥2.5 m/sec in 26/78 (33.3%) evaluated. The frequency of obstruction, restriction, or abnormal gas exchange found on lung function evaluation was not significantly different in subjects with and without TRJV elevation. However, significant inverse correlations were observed between TRJV and both % predicted forced vital capacity (FVC) (r = −0.29, P = 0.022) and oxygen saturation (r = −0.26, P = 0.036). When compared to subjects without TRJV elevation, subjects with TRJV elevation had significantly lower % predicted forced expiratory volume in 1 sec (FEV1) (78.9 ± 14.4 vs. 86.6 ± 13.0%, P = 0.023), FVC (82.8 ± 14.1 vs. 90.7 ± 12.9%, P = 0.017), and oxygen saturation (95.8 ± 3.2 vs. 97.5 ± 2.4%, P = 0.016). We found that the combination of low hemoglobin and low % predicted FVC best predicted TRJV elevation (χ2 = 17.05, P = 0.001) in our cohort, correctly identifying 70% of cases and resulting in positive and negative predictive values of 60 and 74%, respectively. We conclude that in this young population with SCD, TRJV elevation that is not significantly associated with abnormal lung function is common at baseline. Pediatr Pulmonol. 2009; 44:281–289. © 2009 Wiley-Liss, Inc.

  • tricuspid regurgitant Jet Velocity is associated with hemolysis in children and young adults with sickle cell disease evaluated for pulmonary hypertension
    Haematologica, 2007
    Co-Authors: Robert I Liem, Luciana T Young, Alexis A Thompson
    Abstract:

    Tricuspid regurgitant Jet Velocity (TRJV) ≥ 2.5 m/sec. on echocardiography is a surrogate marker for pulmonary hypertension (PHT) in adults with sickle cell disease (SCD). We prospectively examined the relationship between TRJV and laboratory markers of hemolysis in 51 children and young adults with SCD at baseline. We found significant correlations between TRJV and lactate dehydrogenase (LDH), hemoglobin (Hb), reticulocyte count (retic) and aspartate aminotransferase (AST). LDH, retic and AST were significantly higher and Hb was lower in subjects with TRJV ≥ 2.5 m/sec. We conclude that hemolysis significantly contributes to TRJV elevation in children and young adults with SCD.

D B Longmore - One of the best experts on this subject based on the ideXlab platform.

  • Magnetic resonance volume flow and Jet Velocity mapping in aortic coarctation
    Journal of the American College of Cardiology, 1993
    Co-Authors: Raad H Mohiaddin, Philip J Kilner, Simon Rees, D B Longmore
    Abstract:

    Objectives. Nuclear magnetic resonance (MRI) Velocity mapping was used to characterize flow waveforms and to measure volume flow in the ascending and descending thoracic aorta in patients with aortic coarctation and in healthy volunteers. We present the method and discuss the relation between these measurements and aortic narrowing assessed by MRI. Finally, we compare coarctation Jet Velocity measured by MRI Velocity mapping with that obtained from continuous wave Doppler echocardiography. Background. The development of a noninvasive imaging method for morphologic visuslization of aortic coarctation and for measurement of its impact on blood flow is highly desirable in the preoperative and postoperative management of patients. Methods. Magnetic resonance imaging phase-shift Velocity mapping was used to measure ascending and descending aortic volume flow in 39 patients with aortic coarctation and in 12 healthy volunteers. Magnetic resonance imaging was also used for anatomic and peak Jet Velocity measurements. The latter were compared with those available from continuous wave Doppler study in 40% of the patients. Results. Whereas ascending aortic volume flow measurement did not show significant differences between the patient and healthy control groups, volume flow curves in the descending aorta did show significant differences between the two groups. Peak volume flow (mean ± SD) was 10.6 ± 5.3 liters/min in patients and 19.6 ± 4.7 liters/min in control subjects (p < 0.001). Time-averaged flow was 2.5 ± 0.9 liters/min in patients and 3.9 ±1.1 liters/min in control subjects (p < 0.05). The descending/ ascending aorta flow ratio was 0.47 ± 0.19 in patients and 0.64 ±0.08 in control subjects (p < 0.05). These variables correlate well with the degree of aortic narrowing. Peak coarctation Jet Velocity measured by MRI Velocity mapping is comparable to that obtained from continuous wave Doppler study (r = 0.95). Conclusions. We established normal ranges for volume flow in the descending aorta and demonstrated abnormalities in patients with aortic coarctation. These abnormalities are likely to be related to resistance to flow imposed by the coarctation and could represent an additional index for monitoring patients before and after intervention.

  • magnetic resonance Jet Velocity mapping in mitral and aortic valve stenosis
    Circulation, 1993
    Co-Authors: Philip J Kilner, Carla Manzara, Raad H Mohiaddin, Dudley J Pennell, M G Sutton, David N Firmin, S R Underwood, D B Longmore
    Abstract:

    BACKGROUND Magnetic resonance (MR) phase-shift Velocity mapping is an established method for measurement of nonturbulent intravascular flow. Shortening the echo time of the MR sequence to 3.6 msec allowed application of the technique to turbulent Jet flow. The objective of this study was validation of MR Jet Velocity mapping in patients with cardiac valve stenosis. METHODS AND RESULTS We used a 0.5-T Picker MR machine to measure peak poststenotic Jet Velocity in 15 consecutive patients recruited with known valve disease (six mitral stenosis, three of these restudied after valvoplasty, and 11 aortic stenosis). On the same day as the MR study, these patients underwent independent Doppler echocardiographic measurement of peak Jet Velocity. The results of 10 further MR investigations of aortic stenosis are also reported and compared with Doppler studies performed within 6 months. Of the 29 MR studies, 28 (97%) produced interpretable Velocity maps, the one failure being attributed to misplacement of the imaging slice in a case of severe aortic stenosis. Agreement between MR and Doppler measurements of peak Jet Velocity in the recruited group was as follows: n = 18; range, 1.4-6.1 m/sec; mean, 3 m/sec; mean of differences (MR-Doppler), 0.23 m/sec; standard deviation of differences, 0.49 m/sec. CONCLUSIONS In vivo MR peak Jet Velocity measurements agree well with those made by Doppler ultrasound. The technique, which is not subject to restricted windows of access and has potential for further refinements, could contribute to improved evaluation of stenoses, especially at locations where ultrasonic access is limited.

  • valve and great vessel stenosis assessment with mr Jet Velocity mapping
    Radiology, 1991
    Co-Authors: Philip J Kilner, Raad H Mohiaddin, Dudley J Pennell, David N Firmin, S R Underwood, R S O Rees, Jorge Martinez, D B Longmore
    Abstract:

    For measurement of poststenotic Jet velocities with magnetic resonance (MR) imaging, the authors reduced the echo time (TE) of the field even-echo rephasing (FEER) Velocity mapping sequence from 14.0 to 3.6 msec, so minimizing the problem of MR signal loss from turbulent fluid. In vitro use of rotating disk and stenotic flow phantoms confirmed that the 3.6-msec TE sequence enables accurate measurement of Jet velocities of up to 6.0 m/sec (r = .996). Peak Jet Velocity measurements were made with MR imaging in 36 patients with stenosis of native heart valves (n = 9), conduits (n = 19), or Fontan connections (n = 2) or with aortic coarctation (n = 6). Peak Velocity measurements made with MR imaging agreed well with measurements made with Doppler ultrasound (US), which were available in 18 cases (standard deviation = 0.2 m/sec). Velocity mapping with fast-echo MR imaging is likely to have considerable importance as a noninvasive means of locating and evaluating stenoses, particularly at sites inaccessible to ...

Jamal Naser - One of the best experts on this subject based on the ideXlab platform.

  • The effect of Jet Velocity ratio on aerodynamics of rectangular slot-burners in tangentially-fired furnaces
    2020
    Co-Authors: Shakil Ahmed, James T. Hart, Jamal Naser
    Abstract:

    In a typical coal-fired power station boiler ignition and combustion of coal are largely controlled by burner aerodynamics, hence the geometry of the burner plays an important role in achieving stable combustion, high burnout of fuel, low production of pollutants and control of fouling. Current practice in pulverized coal fired boilers is to use either swirl burners or tangentially-fired slotburners. The later system has been adopted for boilers in Victoria firing brown coal. To obtain a better understanding of the overall combustion process, it is important to investigate the aerodynamics of the Jet development from these burners. Computational Fluid Dynamics (CFD) is an effective tool to investigate aerodynamics of the burners, and this paper presents the results of CFD simulations of several slot-burner models based on real geometries used in coal-fired power stations in Victoria. The CFD software CFX-5 has been used for this study. The effect of the primary to secondary Jet Velocity ratio for different burner geometries has been investigated and the validation of the numerical results has been carried out by comparison with the available measured data. NOMENCLATURE C constant K turbulent kinetic energy S source or sink term U fluid Velocity e dissipation rate Γ diffusion coefficient λ Jet Velocity ratio μ molecular viscosity μT turbulent viscosity ρ density σ turbulent prandtl number INTRODUCTION Victoria’s Latrobe Valley brown coal deposit is unique due to its high moisture content. To minimize furnace fouling and pollutant production and to ensure optimum combustion stability and efficiency when burning this fuel it is necessary to obtain an improved understanding of the relevant combustion and heat transfer processes. Combustion in a coal fired power station boiler can be divided into two parts: ignition and early combustion of the pulverized fuel, which is controlled by the burner and overall combustion and heat transfer which is controlled by the furnace environment. Although a number of extensive studies of swirl burner design and operation have been undertaken (Johnson et al, 1976 and Pleasance, 1980) a comprehensive study of the operation and basis for optimization of slot burners for tangentially-fired boilers is yet to appear in the open literature. In 1981 a research program was initiated to investigate the aerodynamics of a slot burner system. This was seen as the first step towards including details of fluid flow in a general descriptive model of the ignition and early combustion processes in the burner. A review of the available literature (Perry,1982) revealed little information directly relevant to the rectangular Jets. As a result an experimental program was initiated to investigate the influence on isothermal Jet development of primary to secondary Jet Velocity ratio, burner geometry, burner exit Velocity profile and fuel particles in the primary stream. During 1981 the flow development and mixing characteristics were measured in a three-Jet burner model where the burner face was located at the wall and the Jet issued normal to the boiler wall. Perry et al. (1984,1986) conducted some experiments, which investigated the influence of typical secondary to primary Jet Velocity ratio, burner geometry and burner exit Velocity profile on the near field Jet development downstream of the model burners. Further research on the effect of particles in the Jet stream was performed by Yan and Perry (1994). Four simple burner geometries were characterized including a single near rectangular Jet, three Jets discharging at right angles to the furnace wall (geometry A), the three-Jet system discharging at an angle (60°) to the wall with the Jet dividers terminating at the furnace wall (geometry B), the same as geometry B but terminating a short distance upstream of the furnace wall (geometry C) and finally a recessed burner with divergent recess walls (geometry D). Experimental data covers a wide range of secondary to primary Jet Velocity ratios and includes flow visualization observations and transverse Velocity profile and static pressure measurements. From those experiments Perry concluded that burner geometry can significantly influence the Jet development and that the Jet Velocity ratio can have significant influence with a recessed burner. Perry also concluded that for a typical Velocity ratio used in combustion systems, significant deviation of the Jets can occur from the geometric centreline and burner exit Velocity profile variations can influence the subsequent development of the Jet flow field. James et al. (1999) studied in detail three different burner geometries (A, B and D) for Jet Velocity ratio of 1.0. This paper presents the numerical simulation of rectangular slot burners for different Jet Velocity ratios. Geometry C and D have been chosen for investigation as recessed burners can play an important Copyright © 2003 CSIRO Australia 41 role in the development of the Jet. The CFD software CFX-5 has been used in this study. CFX-5 is a coupled solver and uses an unstructured grid. The mathematical model employed to obtain the predictions solves the governing equations for the ensemble-averaged values of the components of the Velocity vector, pressure and turbulence parameters. The k-e model was used for turbulence closure. The results obtained for different Jet Velocity ratio were validated against the available experimental data. MODEL DESCRIPTION The dimensions of the cross section of the primary Jet and the secondary Jet in the cold flow model are (37.5mm x 29mm) and (37.5mmx17mm) respectively. The hydraulic diameter (De) of the Jet is 0.0327m. Upstream of the Jet, the duct length is 1.95m, which is equivalent to 52De. The Jets discharge into the open atmosphere. Due to the symmetry, half of the primary and one full secondary Jet has been simulated, which reduced the CPU time and mesh requirement. Very near to the wall the mesh size was 2.8mm and it gradually increased downstream of the furnace wall. The Y plus value was around 45. The secondary Jet Velocity was kept constant and the primary Jet Velocity was varied to get the required Jet Velocity ratio. The results have been investigated for Jet Velocity ratios (λ) of 1.0, 1.4 and 3.0. The total number of elements used was 1010580. MATHEMATICAL MODELLING The general form of the governing equation can be written as ( ) Φ +       ∂ Φ ∂ Γ ∂ ∂ = Φ ∂ ∂ S x x U x i i i i ρ (1) where ρ, U and Γ are the density, Velocity and the diffusion coefficients. This equation describes the local change of the variable Φ due to convection, diffusion and production under steady state conditions. Depending on Φ, the above equation represents mass, momentum or turbulence quantities. The k-e turbulence model was used in this study. This model solves two transport equations for turbulent kinetic energy and eddy dissipation rate. The two transport equations are ( ) ρe σ μ μ ρ − + = ∇       + ∇ − ∇ G P k Uk

  • Experimental investigation of a rectangular slot-burner in the presence of cross-flow for different Jet Velocity ratios
    2020
    Co-Authors: Shakil Ahmed, James T. Hart, Jamal Naser, Jonian Nikolov, C. Solnorda, William Yang
    Abstract:

    In a typical coal-fired power station boiler the ignition and the combustion are largely controlled by burner aerodynamics, hence the geometry of the burner and the Jet Velocity ratio play an important role in achieving stable combustion, high burnout of fuel, low production of pollutants and control of fouling. Slotburners are used in tangentially fired brown coal boilers in Victoria. To obtain a better understanding of the overall combustion process, it is important to investigate the aerodynamics of the Jet development from these burners. The aim of this paper is to investigate a rectangular slot burner in the presence of cross flow for Jet Velocity ratios of 1.0 and 3.0. A simple burner has been considered for investigation where the Jets discharge at an angle of 60° to the wall. The burner consists of three rectangular slots vertically aligned with the centre known as primary nozzle and the top and bottom ones known as secondary nozzles. The Velocity ratio (φ) is defined as the ratio of secondary to primary Jet Velocity. Laser Doppler Anemometry experiments have been carried out at CSIRO Minerals. In the presence of cross flow, both primary and secondary Jets deviated significantly from the geometric axis towards the wall. Introduction A Jet in cross flow has been the subject of numerous studies because of its wide variety of applications in engineering. Chimney plumes for the dispersion of pollutants in the atmosphere, the cooling of turbine blades, lifting Jets for V/STOL aircraft, fuel injection of burners and Jets of oil and gas entering the flow in oil wells are just a few important examples. Many researchers have studied a circular Jet in cross flow extensively. Foss [6], Andreopoulos [2,3], Andreopoulos and Rodi [4] reported on an extensive investigation of the near field aerodynamics of a round Jet issuing normal to the surface and to the cross flow. Catalano et al. [5] investigated physically and numerically the development of a system for Jet to cross flow Velocity ratio equal to 2.0 and 4.0 where the cross flow was confined between two parallel surfaces. Sherif & Pletcher [17] in surveying numerical and physical modelling studies of Jets in cross flow, consider that these systems are, generally, more difficult to model numerically than wall boundary-layer flows primarily because of the curvature of the shear layer and the complex turbulent flow pattern in the Jet wake region. Sykes et al. [19] developed a time marching solution of the incompressible Navier-Stokes equations and discretized them on to a grid using central spatial differencing on a non-uniform grid. The model was used to investigate the details of the flow within the Jet in cross flow. Smith and Mungal [18] presented the results from extensive imaging of the concentration field of a Jet in cross flow. Lester et al. [11] reported on a series of large-eddy simulations of a round Jet issuing normally into a cross flow. Simulations were performed at two Jet-to-cross flow Velocity ratios, 2.0 and 3.3, and two Reynolds numbers, 1050 and 2100, based on cross flow Velocity and Jet diameter. The mechanisms by which large-scale coherent structures form were described in their investigation. Lim et al. [12] also investigated the development of large-scale structures of a Jet normal to a cross flow. Peterson and Plesniak [15] studied the evolution of a short injection-hole Jet issuing into a cross flow at low blowing ratio by using PIV technique. It is well-established from all of these investigations that a circular Jet in cross flow produces a multitude of vortical structures and the five most significant ones are the leading edge vortices, lee-side vortices, counter-rotating vortex pairs, horseshoe vortices and wake vortices. There are substantially fewer papers dealing with studies of multiple round Jets in cross flow compared to those dealing with a single round Jet in the same environment. Examples of the papers dealing with multiple round Jets include Isaac & Schetz [10], Makihata & Miyai [13], Isaac & Jakubowski [9] and Savory & Toy [16]. Multi-Jet configurations studied include two or three Jets aligned in a row transverse to the cross flow direction, two Jets in tandem and three Jets each located at a corner of an equilateral triangle. Velocity ratios between the Jets equal one, and between the Jet and cross flow range from 2.0 to 10.0. In recent years, various attempts have been made to improve the mixing efficiency of a Jet in cross flow by using non-circular Jet geometry such as an ellipse, square and rectangle. New et al. [14] studied the flow structures of an elliptic Jet in cross flow in a water tunnel using laser-induced fluorescence technique and for a range of Jet aspect ratio from 0.3 to 3.0. A similar investigation was conducted by Haven & Kurosaka [8] to examine the effect of hole exit geometry on the near field characteristics of cross flow Jets. Hole shapes investigated were round, elliptical, square and rectangular. Hart [7] investigated in detail the formation mechanism of large-scale coherent structures of multiple rectangular slot burners without cross flow and for secondary to primary Jet Velocity ratio of 1.0. The effect of Jet Velocity ratio for multiple rectangular slot burners was extensively studied by Ahmed et al. [1] without cross flow. Yan & Perry [20] first investigated the Jet Velocity ratio effect for the rectangular slot burners in the presence of cross flow. They studied the flow by visualization and took measurements for mean Velocity by Laser Doppler Anemometry (LDA) in the near field region. The flow pattern in a tangentially fired rectangular slot burner is very complex and needs detailed investigation to understand the mean and turbulent statistics in near and far field region of the Jets. The current work was undertaken to produce more detailed data on mean flow and turbulent stresses in such a flow. The development of the flow field in the near burner region is influenced by burner geometry, Velocity ratio and complex rotational flow in the tangentially fired furnace. In a simple isolated burner study it is not possible to faithfully model all of these influences, particularly the furnace flow field. The cross flow in this isolated burner investigation is the representation of the burner flow field similar to the tangentially fired furnace. Description of the Burner Model A simple burner has been considered for investigation where the Jets discharge at an angle of 60° to the wall. The burner consists of three nozzles vertically aligned with the centre known as primary nozzle and the outer two known as upper and lower secondary nozzles. The burner model is a large box (1.85mx1.5mx1.6m) made from a frame of aluminium with perspex walls. The dimensions of the cross section of the primary nozzle and the secondary nozzles (upper and lower) in the cold flow model are (75mm x 58mm) and (75mm x 34mm) respectively. The hydraulic diameter (De) and the nozzle spacing were 64mm and 27mm respectively. Upstream of the nozzles, the duct length was 1.2m, to give a more developed Velocity profile at the exit of the burner. The dimension of the cross section of the cross flow nozzle was (75mm x 252mm) and the duct length was 1.8m. Figure 1(a) and 1(b) show the dimensions of the flow containment box, primary and secondary nozzles respectively.

  • Investigation of aerodynamics of a recessed rectangular slot-burner used in tangentially-fired furnaces by varying Jet Velocity ratio in the presence of cross-flow
    Experimental Thermal and Fluid Science, 2015
    Co-Authors: Shakil Ahmed, James T. Hart, Jonian Nikolov, Christopher B Solnordal, William Yang, Jamal Naser
    Abstract:

    Abstract The power generation industry throughout the world stands to gain significantly from process improvements and optimization which can potentially lead to cleaner production of cost effective electricity. The efficient operation of lignite-based tangentially-fired combustion systems, as commonly used in Victoria, Australia, depends on critical issues such as ignition and combustion of the fuel, which are largely controlled by burner aerodynamics. The geometry of the burner and the ratio of velocities between the primary and secondary Jets play an important role in achieving stable combustion, high burnout of fuel, low production of pollutants and control of fouling. Slot-burners are vertically aligned stacks of rectangular nozzles delivering primary fuel and secondary air Jets, and are commonly used in tangentially-fired boilers. To obtain a better understanding of the overall combustion process, it is important to understand the aerodynamics of Jet development from these burners. This paper reports an experimental investigation into the aerodynamics of a recessed rectangular slot-burner of the type used in the Yallourn stage-2 tangentially-fired furnace. The 1:15 scale model burner consisted of a central (primary) rectangular fuel nozzle with two secondary rectangular air Jets positioned above and below it. The burner Jets were at an angle of 60° to the wall and were diffused and mixed in a recess before entering into the measurement vessel. A cross-flow Jet was attached to the wall of the vessel to simulate the recirculation similar to tangentially-fired furnaces. Experiments for both single and two-phase flow were performed. For single-phase flow, the air flow was seeded with a fine mist of sugar particles (mean diameter 1 μm) introduced into the primary, secondary and cross-flow ducts. For two-phase flow, solid glass spheres (mean diameter 66 μm, density 2450 kg/m 3 ) were used as the representative of the coal particles and were introduced only at the centre of the primary duct from a bubbling fluidized bed. Experiments were conducted using a primary to cross-flow Jet Velocity ratio ( φ ) of 1.0 and secondary to primary Jet Velocity ratios ( ϕ ) of 1.0 and 3.0 as found in real furnaces. Laser Doppler Anemometry (LDA) was used to measure mean and turbulent Velocity components in the near field and downstream regions of the Jets. The flow pattern inside the recess was very complex and greatly influenced the flow where it entered the measurement vessel. For single-phase flow and ϕ  = 1.0, the Jets diverged completely from the geometric axis of the burner and attached to the wall. The degree of deflection of the lower secondary Jet was slightly more than the primary Jet. For ϕ  = 3.0, after exiting from the nozzle, the primary Jet diffused outwards and mixed with the higher momentum secondary Jets in the recess and came out with the secondary Jets. For two-phase flow and ϕ  = 1.0, in the mixing region between the primary and cross-flow Jet, the gas-phase velocities were higher than the particle-phase. Further downstream the peak velocities of the particle-phase slightly deviated and occurred farther from the wall. For ϕ  = 3.0, downstream of the nozzle there was a tendency of separation for the gas-phase near the wall while the particle-phase was attached to the wall.

  • the effect of Jet Velocity ratio on aerodynamics of a rectangular slot burner in the presence of cross flow
    Experimental Thermal and Fluid Science, 2007
    Co-Authors: Shakhil Ahmed, James T. Hart, Jonian Nikolov, Christopher B Solnordal, William Yang, Jamal Naser
    Abstract:

    In a typical coal-fired power station boiler the ignition and the combustion of the fuel is largely controlled by burner aerodynamics. An experimental and numerical study of the rectangular slot-burners widely used on power stations in Victoria, Australia has been conducted to improve understanding of Jet development within the boiler. The 1:15 scale model burner consisted of a central (primary) rectangular fuel nozzle with two (secondary) rectangular air Jets positioned above and below it. The burner Jets entered the measurement vessel at an angle of 60 deg to the wall. A cross-flow Jet was attached to the wall of the vessel to simulate the recirculation prevalent in power station boilers. Experiments were conducted using a primary to cross-flow Jet Velocity ratio ({phi}) of 1.0 and secondary to primary Jet Velocity ratios ({phi}) of 1.0 and 3.0. Laser Doppler Anemometry (LDA) was used to measure mean and turbulent Velocity components in the near field and downstream regions of the Jets. Cross-flow significantly influenced the near field flow development from the slot-burner by deviating both primary and secondary Jets from their geometric axes towards the wall. The degree of deviation was greater for {phi} = 1.0 since the higher Velocity secondary Jetsmore » increased the overall momentum of the primary Jet for {phi} = 3.0. A numerical investigation of the rectangular slot-burner was also performed. First, the numerical results were validated against the experimental results and then visualization of the developing flow field was used to reveal the finer details of the cross-flow/burner Jet interaction. Agreement between numerical and experimental Jet features was good, although the numerical results predicted a primary Jet that was marginally too narrow. Also the predicted downstream behaviour for {phi} = 3.0 deviated more significantly from experimental observation. Using the SST turbulence model, the numerical results suggested that a twin vortex was generated behind the initial region of the primary Jet and this would aid in mixing of gas and fuel between primary and secondary Jets. (author)« less

Mark T Gladwin - One of the best experts on this subject based on the ideXlab platform.

  • an elevated tricuspid regurgitant Jet Velocity in sickle cell disease is associated with polymorphisms in genes impacting innate immunity
    Blood, 2011
    Co-Authors: Clinton T Baldwin, Gregory J Kato, Mark T Gladwin, Allison E Ashleykoch, Melanie E Garrett, Karen L Soldano, James G Taylor, Marilyn J Telen, Paola Sebastiani, Martin H Steinberg
    Abstract:

    Abstract 514 An elevated tricuspid regurgitant Jet Velocity (TRV) by echocardiography, associated with increased mortality risk, may be reflective of pulmonary and systemic vasculopathy in sickle cell disease (SCD). The epidemiologic associations between an elevated TRV and other sub-phenotypes of SCD, such as leg ulcers, priapism, proteinuria and increased rate of hemolysis, suggest a common pathogenic link across vascular beds. We were interested in identifying genetic modifiers of SCD and hypothesized that an elevated TRV is, in part, genetically determined. Previous candidate gene studies identified single nucleotide polymorphisms (SNPs) in activin A receptor, type II-like 1 ( ACVRL1 ), bone morphogenetic receptor 2 ( BMPR2 ) and bone morphogenetic protein 6 ( BMP6 ) associated with an elevated TRV suggesting a role for the TGF-b pathway in pathogenesis. We performed a genome-wide association study (GWAS) to identify novel genes and pathways that might be associated with an elevated TRV. We first used Illumina 610K arrays in a GWAS on 340 sickle cell disease patients recruited as part of the observational arm of the Pulmonary Hypertension and Sickle Cell Disease with Sildenafil Therapy (Walk-PHaSST) clinical trial (discovery set) and then validated these results using a replication set consisting of 56 patients enrolled in the studies of TRV and SCD at Duke and Boston Universities. All subjects were 17 years or older and had the HbS only phenotype. We analyzed the data using TRV as a continuous variable and we adjusted for potential confounding effects of age and gender. In addition, as there were 9 different clinical centers in the discovery set, we used center-adjusted TRV values for the analysis. We identified 3 SNPs in CUB and sushi multiple domains 1 ( CSMD1 ) (rs12674750, p=9.5 × 10 −6 , rs7008391, p=1.8×10 −5 , rs4433172, p=4.1×10 −5 ) and 1 in sorting nexin 31 ( SNX31 ) (rs1609, p=8.2×10 −5 ), also on chromosome 8q, which were also identified in our replication set (p=0.04 for CSMD1 SNPs and 0.01 for SNX31 ). CSMD1 is a very large gene of more than 2 Mb and the 610 array includes 1710 SNPs in this gene. However, the probability that we observe 3 SNPs replicated in this gene in a sample size of 56 by chance is only 0.0005. Additionally, 2 SNPs in the mediator of innate immunity, lymphocyte antigen 86 ( LY86 ) (rs3827783, p=3.89×10 −6 , rs9502483, p=1.02×10 −5 ), were identified in our discovery set. We evaluated the top 5 SNPs originally identified in the candidate gene studies and found that 4 were not present on the 610K arrays. The remaining one had a p-value of 0.17 but is in linkage dysequilibrium with another SNP in BMP6 (rs7450930), a rare variant, with a p-value of 2.5 × 10 −5 . CSMD1 inhibits the classical pathway of complement activation and complement-mediated hemolysis in rats. This is of interest in SCD because of recent data linking cell-free heme and immune modulation. These findings suggest that sickle cell disease patients with an elevated TRV have altered innate immunity and that sickle vasculopathy may be associated with dysregulation of inflammation. Disclosures: No relevant conflicts of interest to declare.

  • elevated tricuspid regurgitant Jet Velocity in children and adolescents with sickle cell disease association with hemolysis and hemoglobin oxygen desaturation
    Haematologica, 2009
    Co-Authors: Caterina P. Minniti, Craig Sable, Andrew D Campbell, Sohail Rana, Gregory Ensing, Niti Dham, Onyinye Onyekwere, Mehdi Nouraie, Gregory J Kato, Mark T Gladwin
    Abstract:

    Background Elevation of echocardiography-determined tricuspid regurgitant Jet Velocity predicts high systolic pulmonary artery pressure and early mortality in adults with sickle cell disease. The definition, prevalence and clinical correlates of elevated Jet Velocity have not been established in pediatric patients. The present study tested the hypotheses that elevated Jet Velocity affects 10% of pediatric patients, is associated with both hemolysis and hypoxia, and has clinical correlates with acute chest syndrome, stroke, transfusion requirement and abnormal 6-minute walk test results. Design and Methods A prospective multicenter study of 310 patients aged 3–20 years old with sickle cell disease under basal conditions and 54 matched controls was conducted. A hemolytic index was generated by principal component analysis of the levels of lactate dehydrogenase, aspartate aminotransferase and bilirubin and reticulocyte count. Results Elevated Jet Velocity (defined as ≥2.60 m/sec based on the mean±2 SD in controls) occurred in 32 patients (11.0%) including one child of 3 years old. After adjustment for hemoglobin concentration, systolic blood pressure and left ventricular diastolic function, a 2 SD increase in the hemolytic index was associated with a 4.5-fold increase in the odds of elevated Jet Velocity ( p =0.009) and oxygen saturation ≤98% with a 3.2-fold increase ( p =0.028). Two or more episodes of acute chest syndrome had occurred in 28% of children with elevated Jet Velocity compared to in 13% of other children ( p =0.012), more than ten units of blood had been transfused in 39% versus 18% ( p =0.017) and stroke had occurred in 19% versus 11% ( p =0.2). The distance walked in 6-minute walk tests did not differ significantly, but oxygen saturation declined during the tests in 68% of children with elevated Jet Velocity compared to in 32% of other children ( p =0.0002). Conclusions According to a pediatric-specific definition the prevalence of elevated Jet Velocity in this population of young patients with sickle cell disease was 11%. The study provides evidence for independent associations of elevated Jet Velocity with hemolysis and oxygen desaturation. Further investigations should address whether elevated Jet Velocity may indicate future complications and whether early intervention is beneficial.

  • Correlations Between Cytokines and Elevated Tricuspid Regurgitant Jet Velocity in Children and Adolescents with Sickle Cell Disease
    Blood, 2008
    Co-Authors: Mehdi Nouraie, Caterina P. Minniti, Craig Sable, Andrew D Campbell, Sohail Rana, Gregory J Kato, Mark T Gladwin, Oswaldo Castro, Tatiana Ammosova
    Abstract:

    Background:The pathogenesis of pulmonary hypertension in sickle cell disease is not fully defined. We have found independent associations of hemolysis and hemoglobin oxygen desaturation with elevated tricuspid regurgitant Jet Velocity in a prospective multicenter study of 310 children and adolescents with sickle cell disease. The present report includes a subset of these patients in whom we investigated the association with Jet Velocity of an array of cytokines and biomediators that have previously been associated with vasculopathy and primary or secondary hypertension. Methods:Jet Velocity was prospectively determined by Doppler echocardiograph in 237 children and adolescents with sickle cell disease at steady state. Elevated Jet Velocity was defined as ≥2.6 m/sec based on the mean + 2 SD in control subjects matched by age, sex and ethnicity to every sixth patient. Plasma concentrations of interleukins-6, 8 and10, interferon-γ, tumor necrosis factor-α, vascular endothelial growth factor (VEGF), monocyte chemoattractant protein-1 (MCP-1), basic fibroblast growth factor (bFGF), platelet-derived growth factor-BB (PDGF-BB) and Regulated upon Activation Normal T-cell Expressed and Secreted (RANTES) were determined by a multiplex cytokine kit and the Bio-Plex suspension array system (Bio-Rad, Hercules, CA). Plasma concentrations of endothelin-1 and serum concentrations of erythropoietin were analyzed by ELISA (R&D Systems, Minneapolis, MN). Levels of significance were adjusted for multiple comparisons. A hemolytic index was derived by principle component analysis of reticulocyte count, aspartate aminotransferase, total bilirubin and lactate dehydrogenase. Oxygen saturation of hemoglobin was determined by pulse oximetry. Results:Interleukins-8 and 10, VEGF and erythropoietin were significantly increased in sickle cell disease patients compared with controls while RANTES was significantly decreased. Among patients with sickle cell disease, interleukins-6 and 8, interferon-γ, tumor necrosis factor-α, PDGF-bb, erythropoietin and RANTES had significant positive correlations with Jet Velocity in bivariate analyses. Of these, only interleukin-8 and erythropoietin correlated significantly with the hemolytic index in bivariate analyses. By logistic regression, interleukin-6 (p = 0.020) and PDGF-bb (P = 0.003) were independently associated with increased odds of elevated Jet Velocity while VEGF was independently associated with decreased odds (P = 0.004). These associations persisted after adjustment either for the degree of hemolysis or for hemoglobin oxygen saturation. Conclusion: Similar to observations in primary and experimental pulmonary hypertension, altered expression of interleukin-6, PDGF-bb and VEGF may be associated with the development of pulmonary hypertension in children with sickle cell disease. At least some of these effects may be additive to those of hemolysis and hypoxia. Further investigations of these pathways may be appropriate in the search for new therapeutic modalities.

  • Pulmonary Function Tests and Their Correlation with Tricuspid Regurgitant Jet Velocity in Pediatric Sickle Cell Disease Patients.
    Blood, 2007
    Co-Authors: Manuel Arteta, Caterina P. Minniti, Craig Sable, Andrew D Campbell, Sohail Rana, Gregory Ensing, Gregory J Kato, Deepika S. Darbari, Onyekwere Onyinye, Mark T Gladwin
    Abstract:

    Background: Adults and children with sickle cell disease (SCD) often have a restrictive pattern of pulmonary function and decreased DLCO. Echocardiography-determined tricuspid regurgitation Jet Velocity (TRV) ≥2.5 m/s occurs in about 30% of adults with SCD and is associated with increased mortality. Its prevalence and significance in children has not been established. We prospectively evaluated pulmonary function tests and their relationship to TRV in a multicenter study of children with SCD. Methods: Patients with SCD (Hb SS, SC, Sb thalassemia or other major sickling phenotypes) aged 7 to 20 years were evaluated clinically and with spirometry, plethysmography, diffusing capacity, and echocardiography under basal circumstances. Controls were matched by ethnicity, sex and age to every sixth patient with SCD studied. Results: Pulmonary function testing was performed in 115 of 267 children enrolled in the study as of August 2007 (93 had SCD and 22 were controls). TRV was measurable in 71 patients and 18 controls who had pulmonary function tests performed. FEV1 and FVC were significantly lower in children with SCD compared to controls and TRV was significantly higher, but FV1/FVC and TLC were not different. Among children with SCD, a higher TRV was associated with lower values for FEV1, FVC FEV1/FVC and TLC but not DLCO. Conclusions: Similar to adults, pediatric patients with SCD had lower FEV1 and FVC than controls but almost identical FEV1/FVC suggesting restrictive lung dysfunction. In contrast to adults, DLCO was not lower among pediatric SCD patients than controls. Lower FEV1/FVC, a marker of obstructive lung dysfunction, correlated with higher TRV as did lower FVC and TLC, markers of restrictive lung dysfunction.