The Experts below are selected from a list of 15177 Experts worldwide ranked by ideXlab platform
Duncan J. Maitland - One of the best experts on this subject based on the ideXlab platform.
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A shape memory polymer dialysis needle adapter for the reduction of Hemodynamic Stress within arteriovenous grafts
IEEE Transactions on Biomedical Engineering, 2007Co-Authors: Jason M. Ortega, Jeffrey Loge, Ward Small, Thomas S. Wilson, William Benett, Duncan J. MaitlandAbstract:A deployable, shape memory polymer adapter is investigated for reducing the Hemodynamic Stress caused by dialysis needle flow impingement within an arteriovenous graft. Computational fluid dynamics simulations of dialysis sessions with and without the adapter demonstrate that the adapter provides a significant decrease in the wall shear Stress. Preliminary in vitro flow visualization measurements are made within a graft model following delivery and actuation of a prototype shape memory polymer adapter. Both the simulations and the qualitative flow visualization measurements demonstrate that the adapter reduces the severity of the dialysis needle flow impingement on the vascular access graft.
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A Shape Memory Polymer Dialysis Needle Adapter for the Reduction of Hemodynamic Stress within Arteriovenous Grafts
2006Co-Authors: Jason M. Ortega, Jeffrey Loge, Ward Small, Thomas S. Wilson, William Benett, Duncan J. MaitlandAbstract:A deployable, shape memory polymer adapter is investigated for reducing the Hemodynamic Stress caused by a dialysis needle flow within an arteriovenous graft. Computational fluid dynamics simulations of dialysis sessions with and without the adapter demonstrate that the adapter provides a significant decrease in the wall shear Stress. In vitro flow visualization measurements are made within a graft model following delivery and actuation of a prototype shape memory polymer adapter. Vascular access complications resulting from arteriovenous (AV) graft failures account for over $1 billion per year in the health care costs of dialysis patients in the U.S.[1] The primary mode of failure of arteriovenous fistulas (AVF's) and polytetrafluoroethylene (PTFE) grafts is the development of intimal hyperplasia (IH) and the subsequent formation of stenotic lesions, resulting in a graft flow decline. The Hemodynamic Stresses arising within AVF's and PTFE grafts play an important role in the pathogenesis of IH. Studies have shown that vascular damage can occur in regions where there is flow separation, oscillation, or extreme values of wall shear Stress (WSS).[2] Nevaril et al.[3] show that exposure of red blood cells to WSS's on the order of 1500 dynes/cm2 can result in hemolysis. Hemodynamic Stress from dialysis needle flow more » has recently been investigated for the role it plays in graft failure. Using laser Doppler velocimetry measurements, Unnikrishnan et al.[4] show that turbulence intensities are 5-6 times greater in the AV flow when the needle flow is present and that increased levels of turbulence exist for approximately 7-8cm downstream of the needle. Since the AVF or PTFE graft is exposed to these high levels of Hemodynamic Stress several hours each week during dialysis sessions, it is quite possible that needle flow is an important contributor to vascular access occlusion.[4] We present a method for reducing the Hemodynamic Stress in an AV graft by tailoring the fluid dynamics of the dialysis needle flow using a deployable shape memory polymer (SMP) dialysis needle adapter. Such an adapter is deployed through the needle into the graft where it is actuated into an expanded shape using thermal energy. The expanded adapter has a tube-like shape, in which the distal end has a larger cross-sectional area than that of the needle. When the dialysis session is completed, the adapter is retracted through the needle. In this initial study, we conduct computational fluid dynamics (CFD) simulations to assess the changes in the Hemodynamic Stress on a graft wall when the SMP adapter is utilized. Additionally, we fabricate a prototype SMP adapter and deploy it in an in vitro model of an AV graft. « less
Yoshikatsu Saiki - One of the best experts on this subject based on the ideXlab platform.
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A novel biodegradable external mesh stent improved long-term patency of vein grafts by inhibiting intimal–medial hyperplasia in an experimental canine model
General Thoracic and Cardiovascular Surgery, 2016Co-Authors: Atsuhiko Sato, Shunsuke Kawamoto, Mika Watanabe, Yusuke Suzuki, Goro Takahashi, Naoki Masaki, Kiichiro Kumagai, Yoshifumi Saijo, Koichi Tabayashi, Yoshikatsu SaikiAbstract:Objectives Increased Hemodynamic Stress on vein grafts used in the arterial system is associated with vein graft disease. We determined whether a novel biodegradable external mesh stent could inhibit medial–intimal hyperplasia by suppressing Hemodynamic Stress on vein grafts and improve long-term patency. Methods Twenty-four beagles underwent bilateral femoral interposition grafting using reversed femoral veins. Vein grafts were externally supported by a novel poly l -lactide-ε-caprolactone copolymer (P(LA/CL)) biodegradable mesh stent or a nonabsorbable mesh stent. Vein grafts with no reinforcement were used as controls. The grafts were harvested 6 and 12 months after implantation for morphometric and immunohistochemical assessment. Results The endoluminal circumferential vein graft length was smaller in the P(LA/CL) and nonabsorbable groups (17.2 ± 2.9 and 19.0 ± 0.3 mm, respectively), than that in the control group (25.0 ± 2.6 mm, P
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A novel biodegradable external mesh stent improved long-term patency of vein grafts by inhibiting intimal–medial hyperplasia in an experimental canine model
General thoracic and cardiovascular surgery, 2015Co-Authors: Atsuhiko Sato, Shunsuke Kawamoto, Mika Watanabe, Yusuke Suzuki, Goro Takahashi, Naoki Masaki, Kiichiro Kumagai, Yoshifumi Saijo, Koichi Tabayashi, Yoshikatsu SaikiAbstract:Objectives Increased Hemodynamic Stress on vein grafts used in the arterial system is associated with vein graft disease. We determined whether a novel biodegradable external mesh stent could inhibit medial–intimal hyperplasia by suppressing Hemodynamic Stress on vein grafts and improve long-term patency.
William Benett - One of the best experts on this subject based on the ideXlab platform.
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A shape memory polymer dialysis needle adapter for the reduction of Hemodynamic Stress within arteriovenous grafts
IEEE Transactions on Biomedical Engineering, 2007Co-Authors: Jason M. Ortega, Jeffrey Loge, Ward Small, Thomas S. Wilson, William Benett, Duncan J. MaitlandAbstract:A deployable, shape memory polymer adapter is investigated for reducing the Hemodynamic Stress caused by dialysis needle flow impingement within an arteriovenous graft. Computational fluid dynamics simulations of dialysis sessions with and without the adapter demonstrate that the adapter provides a significant decrease in the wall shear Stress. Preliminary in vitro flow visualization measurements are made within a graft model following delivery and actuation of a prototype shape memory polymer adapter. Both the simulations and the qualitative flow visualization measurements demonstrate that the adapter reduces the severity of the dialysis needle flow impingement on the vascular access graft.
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A Shape Memory Polymer Dialysis Needle Adapter for the Reduction of Hemodynamic Stress within Arteriovenous Grafts
2006Co-Authors: Jason M. Ortega, Jeffrey Loge, Ward Small, Thomas S. Wilson, William Benett, Duncan J. MaitlandAbstract:A deployable, shape memory polymer adapter is investigated for reducing the Hemodynamic Stress caused by a dialysis needle flow within an arteriovenous graft. Computational fluid dynamics simulations of dialysis sessions with and without the adapter demonstrate that the adapter provides a significant decrease in the wall shear Stress. In vitro flow visualization measurements are made within a graft model following delivery and actuation of a prototype shape memory polymer adapter. Vascular access complications resulting from arteriovenous (AV) graft failures account for over $1 billion per year in the health care costs of dialysis patients in the U.S.[1] The primary mode of failure of arteriovenous fistulas (AVF's) and polytetrafluoroethylene (PTFE) grafts is the development of intimal hyperplasia (IH) and the subsequent formation of stenotic lesions, resulting in a graft flow decline. The Hemodynamic Stresses arising within AVF's and PTFE grafts play an important role in the pathogenesis of IH. Studies have shown that vascular damage can occur in regions where there is flow separation, oscillation, or extreme values of wall shear Stress (WSS).[2] Nevaril et al.[3] show that exposure of red blood cells to WSS's on the order of 1500 dynes/cm2 can result in hemolysis. Hemodynamic Stress from dialysis needle flow more » has recently been investigated for the role it plays in graft failure. Using laser Doppler velocimetry measurements, Unnikrishnan et al.[4] show that turbulence intensities are 5-6 times greater in the AV flow when the needle flow is present and that increased levels of turbulence exist for approximately 7-8cm downstream of the needle. Since the AVF or PTFE graft is exposed to these high levels of Hemodynamic Stress several hours each week during dialysis sessions, it is quite possible that needle flow is an important contributor to vascular access occlusion.[4] We present a method for reducing the Hemodynamic Stress in an AV graft by tailoring the fluid dynamics of the dialysis needle flow using a deployable shape memory polymer (SMP) dialysis needle adapter. Such an adapter is deployed through the needle into the graft where it is actuated into an expanded shape using thermal energy. The expanded adapter has a tube-like shape, in which the distal end has a larger cross-sectional area than that of the needle. When the dialysis session is completed, the adapter is retracted through the needle. In this initial study, we conduct computational fluid dynamics (CFD) simulations to assess the changes in the Hemodynamic Stress on a graft wall when the SMP adapter is utilized. Additionally, we fabricate a prototype SMP adapter and deploy it in an in vitro model of an AV graft. « less
Jeffrey Loge - One of the best experts on this subject based on the ideXlab platform.
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A shape memory polymer dialysis needle adapter for the reduction of Hemodynamic Stress within arteriovenous grafts
IEEE Transactions on Biomedical Engineering, 2007Co-Authors: Jason M. Ortega, Jeffrey Loge, Ward Small, Thomas S. Wilson, William Benett, Duncan J. MaitlandAbstract:A deployable, shape memory polymer adapter is investigated for reducing the Hemodynamic Stress caused by dialysis needle flow impingement within an arteriovenous graft. Computational fluid dynamics simulations of dialysis sessions with and without the adapter demonstrate that the adapter provides a significant decrease in the wall shear Stress. Preliminary in vitro flow visualization measurements are made within a graft model following delivery and actuation of a prototype shape memory polymer adapter. Both the simulations and the qualitative flow visualization measurements demonstrate that the adapter reduces the severity of the dialysis needle flow impingement on the vascular access graft.
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A Shape Memory Polymer Dialysis Needle Adapter for the Reduction of Hemodynamic Stress within Arteriovenous Grafts
2006Co-Authors: Jason M. Ortega, Jeffrey Loge, Ward Small, Thomas S. Wilson, William Benett, Duncan J. MaitlandAbstract:A deployable, shape memory polymer adapter is investigated for reducing the Hemodynamic Stress caused by a dialysis needle flow within an arteriovenous graft. Computational fluid dynamics simulations of dialysis sessions with and without the adapter demonstrate that the adapter provides a significant decrease in the wall shear Stress. In vitro flow visualization measurements are made within a graft model following delivery and actuation of a prototype shape memory polymer adapter. Vascular access complications resulting from arteriovenous (AV) graft failures account for over $1 billion per year in the health care costs of dialysis patients in the U.S.[1] The primary mode of failure of arteriovenous fistulas (AVF's) and polytetrafluoroethylene (PTFE) grafts is the development of intimal hyperplasia (IH) and the subsequent formation of stenotic lesions, resulting in a graft flow decline. The Hemodynamic Stresses arising within AVF's and PTFE grafts play an important role in the pathogenesis of IH. Studies have shown that vascular damage can occur in regions where there is flow separation, oscillation, or extreme values of wall shear Stress (WSS).[2] Nevaril et al.[3] show that exposure of red blood cells to WSS's on the order of 1500 dynes/cm2 can result in hemolysis. Hemodynamic Stress from dialysis needle flow more » has recently been investigated for the role it plays in graft failure. Using laser Doppler velocimetry measurements, Unnikrishnan et al.[4] show that turbulence intensities are 5-6 times greater in the AV flow when the needle flow is present and that increased levels of turbulence exist for approximately 7-8cm downstream of the needle. Since the AVF or PTFE graft is exposed to these high levels of Hemodynamic Stress several hours each week during dialysis sessions, it is quite possible that needle flow is an important contributor to vascular access occlusion.[4] We present a method for reducing the Hemodynamic Stress in an AV graft by tailoring the fluid dynamics of the dialysis needle flow using a deployable shape memory polymer (SMP) dialysis needle adapter. Such an adapter is deployed through the needle into the graft where it is actuated into an expanded shape using thermal energy. The expanded adapter has a tube-like shape, in which the distal end has a larger cross-sectional area than that of the needle. When the dialysis session is completed, the adapter is retracted through the needle. In this initial study, we conduct computational fluid dynamics (CFD) simulations to assess the changes in the Hemodynamic Stress on a graft wall when the SMP adapter is utilized. Additionally, we fabricate a prototype SMP adapter and deploy it in an in vitro model of an AV graft. « less
Jason M. Ortega - One of the best experts on this subject based on the ideXlab platform.
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A shape memory polymer dialysis needle adapter for the reduction of Hemodynamic Stress within arteriovenous grafts
IEEE Transactions on Biomedical Engineering, 2007Co-Authors: Jason M. Ortega, Jeffrey Loge, Ward Small, Thomas S. Wilson, William Benett, Duncan J. MaitlandAbstract:A deployable, shape memory polymer adapter is investigated for reducing the Hemodynamic Stress caused by dialysis needle flow impingement within an arteriovenous graft. Computational fluid dynamics simulations of dialysis sessions with and without the adapter demonstrate that the adapter provides a significant decrease in the wall shear Stress. Preliminary in vitro flow visualization measurements are made within a graft model following delivery and actuation of a prototype shape memory polymer adapter. Both the simulations and the qualitative flow visualization measurements demonstrate that the adapter reduces the severity of the dialysis needle flow impingement on the vascular access graft.
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A Shape Memory Polymer Dialysis Needle Adapter for the Reduction of Hemodynamic Stress within Arteriovenous Grafts
2006Co-Authors: Jason M. Ortega, Jeffrey Loge, Ward Small, Thomas S. Wilson, William Benett, Duncan J. MaitlandAbstract:A deployable, shape memory polymer adapter is investigated for reducing the Hemodynamic Stress caused by a dialysis needle flow within an arteriovenous graft. Computational fluid dynamics simulations of dialysis sessions with and without the adapter demonstrate that the adapter provides a significant decrease in the wall shear Stress. In vitro flow visualization measurements are made within a graft model following delivery and actuation of a prototype shape memory polymer adapter. Vascular access complications resulting from arteriovenous (AV) graft failures account for over $1 billion per year in the health care costs of dialysis patients in the U.S.[1] The primary mode of failure of arteriovenous fistulas (AVF's) and polytetrafluoroethylene (PTFE) grafts is the development of intimal hyperplasia (IH) and the subsequent formation of stenotic lesions, resulting in a graft flow decline. The Hemodynamic Stresses arising within AVF's and PTFE grafts play an important role in the pathogenesis of IH. Studies have shown that vascular damage can occur in regions where there is flow separation, oscillation, or extreme values of wall shear Stress (WSS).[2] Nevaril et al.[3] show that exposure of red blood cells to WSS's on the order of 1500 dynes/cm2 can result in hemolysis. Hemodynamic Stress from dialysis needle flow more » has recently been investigated for the role it plays in graft failure. Using laser Doppler velocimetry measurements, Unnikrishnan et al.[4] show that turbulence intensities are 5-6 times greater in the AV flow when the needle flow is present and that increased levels of turbulence exist for approximately 7-8cm downstream of the needle. Since the AVF or PTFE graft is exposed to these high levels of Hemodynamic Stress several hours each week during dialysis sessions, it is quite possible that needle flow is an important contributor to vascular access occlusion.[4] We present a method for reducing the Hemodynamic Stress in an AV graft by tailoring the fluid dynamics of the dialysis needle flow using a deployable shape memory polymer (SMP) dialysis needle adapter. Such an adapter is deployed through the needle into the graft where it is actuated into an expanded shape using thermal energy. The expanded adapter has a tube-like shape, in which the distal end has a larger cross-sectional area than that of the needle. When the dialysis session is completed, the adapter is retracted through the needle. In this initial study, we conduct computational fluid dynamics (CFD) simulations to assess the changes in the Hemodynamic Stress on a graft wall when the SMP adapter is utilized. Additionally, we fabricate a prototype SMP adapter and deploy it in an in vitro model of an AV graft. « less