bill liao | 清華大學 - Academia.edu (original) (raw)

Papers by bill liao

ASAIO Journal, 2003

Blood side and dialysate side flow distributions play an important role in determining the optima... more Blood side and dialysate side flow distributions play an important role in determining the optimal use of dialysis membrane in hemodialyzers for the removal of uremic solutes. In this article, we used two nonintrusive magnetic resonance imaging (MRI) techniques called the two-dimensional phase contrast (2DPC) and two-dimensional Fourier transform (2DFT) velocity imaging techniques to (1) study the effect of space yarns on the dialysate side flow distribution, (2) investigate the effect of flow baffle on the dialysate side flow distribution, and (3) characterize the blood side and dialysate side flow profiles of hemodialyzers with flow rates ranging from 200 to 1000 ml/min. We investigated two types of hollow fiber hemodialyzers: hemodialyzers A (with spacer yarns) and B (without spacer yarns). We used a 3 mmol cupric sulfate solution as the compartmental fluid and imaged five transverse cross sections of these hemodialyzers. The hemodialyzer with spacer yarns had a more uniform dialysate side spatial flow distribution than that without spacer yarns. In addition, the design of flow baffle in these hemodialyzers can be further improved to promote uniform dialysate side flow distribution, and the blood side flow had a fully developed laminar flow profile. Our experimental results showed that these velocity imaging techniques provide an innovative, nonintrusive tool for characterizing flow distribution in hemodialyzers.

The International Journal of Artificial Organs, 2004

Experimental approaches to optimize hollow fiber hemodialyzer design are expensive and time-consu... more Experimental approaches to optimize hollow fiber hemodialyzer design are expensive and time-consuming. Computer modeling is an effective way to study mass transfer in the hemodialyzer because a substantial reduction in experimental time and cost can be achieved. This paper presents a two-dimensional modified “equivalent annulus” model, which employs Navier-Stokes (N-S) equations to describe blood and dialysate flow, and Kedem-Katchalsky (K-K) equations to calculate transmembrane flow. N-S equations and K-K equations must be coupled together in the process of computing. The corresponding experiments were designed to validate this model, and experimental results agreed well with numerical results. The distribution of velocity, pressure and solute concentration were investigated in detail, presenting a clear insight into dialyzer mass transfer. This model can be applied to help optimize hemodialyzer design.

Membrane Science and Technology

A nonintrusive experimental tool is useful for a better physical understanding of fluid transport... more A nonintrusive experimental tool is useful for a better physical understanding of fluid transport phenomena in hollow-fiber membrane modules and as test cases for validating, improving, or developing numerical models. In this chapter, we introduced two innovative, nonintrusive flow-imaging techniques using magnetic resonance imaging (MRI) for characterizing fluid transport phenomena in hollow-fiber membrane modules. These flow-imaging techniques are called the 2-D Phase-Contrast (2DPC) and 2-D Fourier-Transform (2DFT) techniques. The principles, validation, advantages, limitations, and some examples of experimental results are presented. We used the 2DPC technique to study the spatial flow distribution and the 2DFT technique to characterize the flow profile and quantify the local ultrafiltration rates in hollow-fiber artificial kidneys (also known as hemodialyzers). These flow-imaging techniques are equally applicable to other hollow-fiber membrane modules.

SIAM Review, 2008

High-frequency oscillations of a rigid sphere in an incompressible viscous fluid moving normal to... more High-frequency oscillations of a rigid sphere in an incompressible viscous fluid moving normal to a rigid plane are considered when the ratio of minimum clearance to sphere radius is small. Asymptotic expansions are constructed that permit an analytical estimate of the force acting on the sphere as a result of its motion. An inner expansion, valid in the neighborhood of the minimum gap, reflects the dominance of viscous effects and fluid inertia. An outer expansion, valid outside the gap, reflects the dominance of fluid inertia with a correction for an oscillating viscous boundary layer. The results are applied to the hydrodynamics of the tapping mode of an atomic force microscope and to the dynamic calibration of its cantilevers.

The Journal of the Acoustical Society of America, 2007

Outer hair cells are critical to the amplification and frequency selectivity of the mammalian ear... more Outer hair cells are critical to the amplification and frequency selectivity of the mammalian ear acting via a fine mechanism called the cochlear amplifier, which is especially effective in the high-frequency region of the cochlea. How this mechanism works under physiological conditions and how these cells overcome the viscous ͑mechanical͒ and electrical ͑membrane͒ filtering has yet to be fully understood. Outer hair cells are electromotile, and they are strategically located in the cochlea to generate an active force amplifying basilar membrane vibration. To investigate the mechanism of this cell's active force production under physiological conditions, a model that takes into account the mechanical, electrical, and mechanoelectrical properties of the cell wall ͑membrane͒ and cochlear environment is proposed. It is shown that, despite the mechanical and electrical filtering, the cell is capable of generating a frequency-tuned force with a maximal value of about 40 pN. It is also found that the force per unit basilar membrane displacement stays essentially the same ͑40 pN/ nm͒ for the entire linear range of the basilar membrane responses, including sound pressure levels close to hearing threshold. Our findings can provide a better understanding of the outer hair cell's role in the cochlear amplifier.

The Journal of the Acoustical Society of America, 2005

Cochlear outer hair cells ͑OHC͒ are critically important for the amplification and sharp frequenc... more Cochlear outer hair cells ͑OHC͒ are critically important for the amplification and sharp frequency selectivity of the mammalian ear. The microchamber experiment has been an effective tool to analyze the OHC high-frequency performance. In this study, the OHC electrical stimulation in the microchamber is simulated. The model takes into account the inertial and viscous properties of fluids inside and outside the cell as well as the viscoelastic and piezoelectric properties of the cell composite membrane ͑wall͒. The closed ends of the cylindrical cell were considered as oscillatory rigid plates. The final solution was obtained in terms of Fourier series, and it was checked against the available results of the microchamber experiment. The conditions of the interaction between the cell and pipette was analyzed, and it was found that the amount of slip along the contact surface has a significant effect on the cell electromotile response. The cell's length changes were computed as a function of frequency, and their dependence on the viscosities of both fluids and the cell wall was analyzed. The distribution of the viscous losses inside the fluids was also estimated. The proposed approach can help in a better understanding of the high-frequency OHC electromotility under experimental and physiological conditions.

The Journal of the Acoustical Society of America, 2005

A computational model is proposed to analyze the active force production in an individual outer h... more A computational model is proposed to analyze the active force production in an individual outer hair cell ͑OHC͒ under high-frequency conditions. The model takes into account important biophysical properties of the cell as well as constraints imposed by the surrounding environment. The biophysical properties include the elastic, piezoelectric, and viscous characteristics of the cell wall. The effect of the environment is associated with the stiffness of the constraint and the drag forces acting on the cell due to the interaction with the external and internal viscous fluids. The study concentrated on a combined effect of the transmembrane potential, frequency, and stiffness of the constraints. The effect of the voltage-dependent stiffness of the cell was particularly investigated and it was found to be twofold. First, it results in higher sensitivity and nonlinearity of the OHC active force production in the physiological range. Second, it determines smaller active forces in the hyperpolarization range. The resonant properties of the active force as functions of voltage and the constraint stiffness were also analyzed. The obtained results can be important for a better understanding of the OHC active force production and the contribution of cell electromotility to the cochlear amplification, sensitivity, and nonlinearity.

Journal of Membrane Science, 2002

... c Baxter Healthcare Corp., McGaw Park, IL 60085, USA. Received 5 July 2001; revised 17 Decemb... more ... c Baxter Healthcare Corp., McGaw Park, IL 60085, USA. Received 5 July 2001; revised 17 December 2001; accepted 20 January 2002. ... The MRFVI was then used to measure the flow in a SYNTRA·160 clinical dialyzer (Baxter Health Care Corp., McGaw Park, IL). ...

Journal of Biomechanical Engineering, 2003

We used an innovative, nonintrusive MRI technique called the two-dimensional (2D) Phase-Contrast ... more We used an innovative, nonintrusive MRI technique called the two-dimensional (2D) Phase-Contrast (2DPC) velocity-imaging technique to investigate the effect of flow baffles on the dialysate-side flow distribution in two different hollow-fiber hemodialyzers (A and B); each with flow rates between 200 and 1000 mL/min (3.33×10−6 and 1.67×10−5 m3/s). Our experimental results show that (1) the dialysate-side flow distribution was nonuniform with channeling flow occurred at the peripheral cross section of these hollow-fiber hemodialyzers, and (2) the existing designs of flow baffles failed to promote uniform dialysate-side flow distribution for all flow rates studies.

Journal of the Association for Research in Otolaryngology, 2005

Cochlear outer hair cell (OHC) electromotility is believed to be responsible for the sensitivity ... more Cochlear outer hair cell (OHC) electromotility is believed to be responsible for the sensitivity and frequency selectivity of the mammalian hearing process. Its contribution to hearing is better understood by examining the force generated by the OHC as a feedback to vibration of the basilar membrane (BM). In this study, we examine the effects of the constraints imposed on the OHC and of the surrounding fluids on the cell's high-frequency active force generated under in vitro and in vivo conditions. The OHC is modeled as a viscoelastic and piezoelectric cylindrical shell coupled with viscous intracellular and extracellular fluids, and the constraint is represented by a spring with adjustable stiffness. The solution is obtained in the form of a Fourier series. The model results are consistent with previously reported experiments under both low-and high-frequency conditions. We find that constrained OHCs achieve a much higher corner frequency than free OHCs, depending on the stiffness of the constraint. We analyze cases in which the stiffness of the constraint is similar to that of the BM, reticular lamina, and tectorial membrane, and find that the force per unit transmembrane potential generated by the OHC can be constant up to several tens of kHz. This model, describing the OHC as a local amplifier, can be incorporated into a global cochlear model that considers cochlear hydrodynamics and frequency modulation of the receptor potential, as well as the graded BM stiffness and OHC length.

ASAIO Journal, 2003

Recent research indicated that the dialysate flow distribution inside a hemodialyzer was not unif... more Recent research indicated that the dialysate flow distribution inside a hemodialyzer was not uniform ("channeling" of the dialysate flows). However, effect of the channeling on the solute clearance has not been directly and quantitatively examined. In this report, a novel experiment approach is presented to test the hypothesis that hollow fibers in different regions within a given hemodialyzer may contribute differently to the solute clearance. Water solution with urea (molecular weight 60) and creatinine (molecular weight 113) were made as "blood," and pure water was used as dialysate. Two high flux dialyzers, dialyzer A (cellulose triacetate) and dialyzer B (polyethersulfone), were used in this study. The hollow fiber potting area at the blood inlet of a dialyzer was divided into equal area concentric rings. In each experiment, only one of the rings was open for blood flow, and the other rings were blocked by epoxy. The "blood" was pumped at 120 ml/min while the dialysate flow rate (Qd) varied at 500, 800, and 1,000 ml/min, respectively. The solute clearance with a specific ring open (local clearance) was determined by measuring solute (urea/creatinine) concentration at the…

ASAIO Journal, 2002

Acute renal failure (ARF) is a major determinant of morbidity and mortality in heart failure. Ear... more Acute renal failure (ARF) is a major determinant of morbidity and mortality in heart failure. Early direct perfusion of the kidney with venous hlood may improve renal function. Methods Used To determine the impact of early Vs late perfusion on renal function, ARF was created in 7 dogs by inducing hemorrhagic shock. Renal artery was cannulated on one side via a percutaneous catheter opposite kidney served as control. Ureters were stented to measure urine output (UO). 3 animals in the late group (LCj were perfused after 1 hour of shock. Following 4 animals in the early group (EC) were perfused within 15 minutes of shock induction. Antegrade perfusion of the kidney was performed using a roller pump at perfusion pressures between 100-1 60 mm Hg using venous blood. Summarize Results: In shock, mean arterial pressure (MAP) was 57.6 2 1.9 mm Hg, mean venous saturation 46.6 26.5 "/o and mean U O 17 2 5.3 YO of the baseline. All perfused kidneys demonstrated recovery of renal function while contro kidneys remained anuric. In perfused kidneys, in spite of higher oxygen delivery (709.5 i 157.0 ml/min Vs 414.0 2 132.0 ml/min, p=0.0081 and higher renal blood flow (1 19 2 14 ml/min Vs 103 If: 38 ml/min, p=0.15) in the LC, U O (98.5 2 20.5 % Vs 39.4 2 lY.3 ' YO of haseline, p<0.001) and CFR (38 2 4 % Vs 24 t 12 % of baseline, p=0.56) were higher in the EC. Conclusion: Early perfusion of kidneys with venous blood provides significantly improved renal function.

ASAIO Journal, 2002

Acute renal failure (ARF) is a major determinant of morbidity and mortality in heart failure. Ear... more Acute renal failure (ARF) is a major determinant of morbidity and mortality in heart failure. Early direct perfusion of the kidney with venous hlood may improve renal function. Methods Used To determine the impact of early Vs late perfusion on renal function, ARF was created in 7 dogs by inducing hemorrhagic shock. Renal artery was cannulated on one side via a percutaneous catheter opposite kidney served as control. Ureters were stented to measure urine output (UO). 3 animals in the late group (LCj were perfused after 1 hour of shock. Following 4 animals in the early group (EC) were perfused within 15 minutes of shock induction. Antegrade perfusion of the kidney was performed using a roller pump at perfusion pressures between 100-1 60 mm Hg using venous blood. Summarize Results: In shock, mean arterial pressure (MAP) was 57.6 2 1.9 mm Hg, mean venous saturation 46.6 26.5 "/o and mean U O 17 2 5.3 YO of the baseline. All perfused kidneys demonstrated recovery of renal function while contro kidneys remained anuric. In perfused kidneys, in spite of higher oxygen delivery (709.5 i 157.0 ml/min Vs 414.0 2 132.0 ml/min, p=0.0081 and higher renal blood flow (1 19 2 14 ml/min Vs 103 If: 38 ml/min, p=0.15) in the LC, U O (98.5 2 20.5 % Vs 39.4 2 lY.3 ' YO of haseline, p<0.001) and CFR (38 2 4 % Vs 24 t 12 % of baseline, p=0.56) were higher in the EC. Conclusion: Early perfusion of kidneys with venous blood provides significantly improved renal function.

ASAIO Journal, 2001

ABSTRACT An abstract is unavailable. This article is available as HTML full text and PDF.

ASAIO Journal, 2003

Blood side and dialysate side flow distributions play an important role in determining the optima... more Blood side and dialysate side flow distributions play an important role in determining the optimal use of dialysis membrane in hemodialyzers for the removal of uremic solutes. In this article, we used two nonintrusive magnetic resonance imaging (MRI) techniques called the two-dimensional phase contrast (2DPC) and two-dimensional Fourier transform (2DFT) velocity imaging techniques to (1) study the effect of space yarns on the dialysate side flow distribution, (2) investigate the effect of flow baffle on the dialysate side flow distribution, and (3) characterize the blood side and dialysate side flow profiles of hemodialyzers with flow rates ranging from 200 to 1000 ml/min. We investigated two types of hollow fiber hemodialyzers: hemodialyzers A (with spacer yarns) and B (without spacer yarns). We used a 3 mmol cupric sulfate solution as the compartmental fluid and imaged five transverse cross sections of these hemodialyzers. The hemodialyzer with spacer yarns had a more uniform dialysate side spatial flow distribution than that without spacer yarns. In addition, the design of flow baffle in these hemodialyzers can be further improved to promote uniform dialysate side flow distribution, and the blood side flow had a fully developed laminar flow profile. Our experimental results showed that these velocity imaging techniques provide an innovative, nonintrusive tool for characterizing flow distribution in hemodialyzers.

The International Journal of Artificial Organs, 2004

Experimental approaches to optimize hollow fiber hemodialyzer design are expensive and time-consu... more Experimental approaches to optimize hollow fiber hemodialyzer design are expensive and time-consuming. Computer modeling is an effective way to study mass transfer in the hemodialyzer because a substantial reduction in experimental time and cost can be achieved. This paper presents a two-dimensional modified “equivalent annulus” model, which employs Navier-Stokes (N-S) equations to describe blood and dialysate flow, and Kedem-Katchalsky (K-K) equations to calculate transmembrane flow. N-S equations and K-K equations must be coupled together in the process of computing. The corresponding experiments were designed to validate this model, and experimental results agreed well with numerical results. The distribution of velocity, pressure and solute concentration were investigated in detail, presenting a clear insight into dialyzer mass transfer. This model can be applied to help optimize hemodialyzer design.

Membrane Science and Technology

A nonintrusive experimental tool is useful for a better physical understanding of fluid transport... more A nonintrusive experimental tool is useful for a better physical understanding of fluid transport phenomena in hollow-fiber membrane modules and as test cases for validating, improving, or developing numerical models. In this chapter, we introduced two innovative, nonintrusive flow-imaging techniques using magnetic resonance imaging (MRI) for characterizing fluid transport phenomena in hollow-fiber membrane modules. These flow-imaging techniques are called the 2-D Phase-Contrast (2DPC) and 2-D Fourier-Transform (2DFT) techniques. The principles, validation, advantages, limitations, and some examples of experimental results are presented. We used the 2DPC technique to study the spatial flow distribution and the 2DFT technique to characterize the flow profile and quantify the local ultrafiltration rates in hollow-fiber artificial kidneys (also known as hemodialyzers). These flow-imaging techniques are equally applicable to other hollow-fiber membrane modules.

SIAM Review, 2008

High-frequency oscillations of a rigid sphere in an incompressible viscous fluid moving normal to... more High-frequency oscillations of a rigid sphere in an incompressible viscous fluid moving normal to a rigid plane are considered when the ratio of minimum clearance to sphere radius is small. Asymptotic expansions are constructed that permit an analytical estimate of the force acting on the sphere as a result of its motion. An inner expansion, valid in the neighborhood of the minimum gap, reflects the dominance of viscous effects and fluid inertia. An outer expansion, valid outside the gap, reflects the dominance of fluid inertia with a correction for an oscillating viscous boundary layer. The results are applied to the hydrodynamics of the tapping mode of an atomic force microscope and to the dynamic calibration of its cantilevers.

The Journal of the Acoustical Society of America, 2007

Outer hair cells are critical to the amplification and frequency selectivity of the mammalian ear... more Outer hair cells are critical to the amplification and frequency selectivity of the mammalian ear acting via a fine mechanism called the cochlear amplifier, which is especially effective in the high-frequency region of the cochlea. How this mechanism works under physiological conditions and how these cells overcome the viscous ͑mechanical͒ and electrical ͑membrane͒ filtering has yet to be fully understood. Outer hair cells are electromotile, and they are strategically located in the cochlea to generate an active force amplifying basilar membrane vibration. To investigate the mechanism of this cell's active force production under physiological conditions, a model that takes into account the mechanical, electrical, and mechanoelectrical properties of the cell wall ͑membrane͒ and cochlear environment is proposed. It is shown that, despite the mechanical and electrical filtering, the cell is capable of generating a frequency-tuned force with a maximal value of about 40 pN. It is also found that the force per unit basilar membrane displacement stays essentially the same ͑40 pN/ nm͒ for the entire linear range of the basilar membrane responses, including sound pressure levels close to hearing threshold. Our findings can provide a better understanding of the outer hair cell's role in the cochlear amplifier.

The Journal of the Acoustical Society of America, 2005

Cochlear outer hair cells ͑OHC͒ are critically important for the amplification and sharp frequenc... more Cochlear outer hair cells ͑OHC͒ are critically important for the amplification and sharp frequency selectivity of the mammalian ear. The microchamber experiment has been an effective tool to analyze the OHC high-frequency performance. In this study, the OHC electrical stimulation in the microchamber is simulated. The model takes into account the inertial and viscous properties of fluids inside and outside the cell as well as the viscoelastic and piezoelectric properties of the cell composite membrane ͑wall͒. The closed ends of the cylindrical cell were considered as oscillatory rigid plates. The final solution was obtained in terms of Fourier series, and it was checked against the available results of the microchamber experiment. The conditions of the interaction between the cell and pipette was analyzed, and it was found that the amount of slip along the contact surface has a significant effect on the cell electromotile response. The cell's length changes were computed as a function of frequency, and their dependence on the viscosities of both fluids and the cell wall was analyzed. The distribution of the viscous losses inside the fluids was also estimated. The proposed approach can help in a better understanding of the high-frequency OHC electromotility under experimental and physiological conditions.

The Journal of the Acoustical Society of America, 2005

A computational model is proposed to analyze the active force production in an individual outer h... more A computational model is proposed to analyze the active force production in an individual outer hair cell ͑OHC͒ under high-frequency conditions. The model takes into account important biophysical properties of the cell as well as constraints imposed by the surrounding environment. The biophysical properties include the elastic, piezoelectric, and viscous characteristics of the cell wall. The effect of the environment is associated with the stiffness of the constraint and the drag forces acting on the cell due to the interaction with the external and internal viscous fluids. The study concentrated on a combined effect of the transmembrane potential, frequency, and stiffness of the constraints. The effect of the voltage-dependent stiffness of the cell was particularly investigated and it was found to be twofold. First, it results in higher sensitivity and nonlinearity of the OHC active force production in the physiological range. Second, it determines smaller active forces in the hyperpolarization range. The resonant properties of the active force as functions of voltage and the constraint stiffness were also analyzed. The obtained results can be important for a better understanding of the OHC active force production and the contribution of cell electromotility to the cochlear amplification, sensitivity, and nonlinearity.

Journal of Membrane Science, 2002

... c Baxter Healthcare Corp., McGaw Park, IL 60085, USA. Received 5 July 2001; revised 17 Decemb... more ... c Baxter Healthcare Corp., McGaw Park, IL 60085, USA. Received 5 July 2001; revised 17 December 2001; accepted 20 January 2002. ... The MRFVI was then used to measure the flow in a SYNTRA·160 clinical dialyzer (Baxter Health Care Corp., McGaw Park, IL). ...

Journal of Biomechanical Engineering, 2003

We used an innovative, nonintrusive MRI technique called the two-dimensional (2D) Phase-Contrast ... more We used an innovative, nonintrusive MRI technique called the two-dimensional (2D) Phase-Contrast (2DPC) velocity-imaging technique to investigate the effect of flow baffles on the dialysate-side flow distribution in two different hollow-fiber hemodialyzers (A and B); each with flow rates between 200 and 1000 mL/min (3.33×10−6 and 1.67×10−5 m3/s). Our experimental results show that (1) the dialysate-side flow distribution was nonuniform with channeling flow occurred at the peripheral cross section of these hollow-fiber hemodialyzers, and (2) the existing designs of flow baffles failed to promote uniform dialysate-side flow distribution for all flow rates studies.

Journal of the Association for Research in Otolaryngology, 2005

Cochlear outer hair cell (OHC) electromotility is believed to be responsible for the sensitivity ... more Cochlear outer hair cell (OHC) electromotility is believed to be responsible for the sensitivity and frequency selectivity of the mammalian hearing process. Its contribution to hearing is better understood by examining the force generated by the OHC as a feedback to vibration of the basilar membrane (BM). In this study, we examine the effects of the constraints imposed on the OHC and of the surrounding fluids on the cell's high-frequency active force generated under in vitro and in vivo conditions. The OHC is modeled as a viscoelastic and piezoelectric cylindrical shell coupled with viscous intracellular and extracellular fluids, and the constraint is represented by a spring with adjustable stiffness. The solution is obtained in the form of a Fourier series. The model results are consistent with previously reported experiments under both low-and high-frequency conditions. We find that constrained OHCs achieve a much higher corner frequency than free OHCs, depending on the stiffness of the constraint. We analyze cases in which the stiffness of the constraint is similar to that of the BM, reticular lamina, and tectorial membrane, and find that the force per unit transmembrane potential generated by the OHC can be constant up to several tens of kHz. This model, describing the OHC as a local amplifier, can be incorporated into a global cochlear model that considers cochlear hydrodynamics and frequency modulation of the receptor potential, as well as the graded BM stiffness and OHC length.

ASAIO Journal, 2003

Recent research indicated that the dialysate flow distribution inside a hemodialyzer was not unif... more Recent research indicated that the dialysate flow distribution inside a hemodialyzer was not uniform (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;channeling&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; of the dialysate flows). However, effect of the channeling on the solute clearance has not been directly and quantitatively examined. In this report, a novel experiment approach is presented to test the hypothesis that hollow fibers in different regions within a given hemodialyzer may contribute differently to the solute clearance. Water solution with urea (molecular weight 60) and creatinine (molecular weight 113) were made as &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;blood,&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; and pure water was used as dialysate. Two high flux dialyzers, dialyzer A (cellulose triacetate) and dialyzer B (polyethersulfone), were used in this study. The hollow fiber potting area at the blood inlet of a dialyzer was divided into equal area concentric rings. In each experiment, only one of the rings was open for blood flow, and the other rings were blocked by epoxy. The &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;blood&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; was pumped at 120 ml/min while the dialysate flow rate (Qd) varied at 500, 800, and 1,000 ml/min, respectively. The solute clearance with a specific ring open (local clearance) was determined by measuring solute (urea/creatinine) concentration at the…

ASAIO Journal, 2002

Acute renal failure (ARF) is a major determinant of morbidity and mortality in heart failure. Ear... more Acute renal failure (ARF) is a major determinant of morbidity and mortality in heart failure. Early direct perfusion of the kidney with venous hlood may improve renal function. Methods Used To determine the impact of early Vs late perfusion on renal function, ARF was created in 7 dogs by inducing hemorrhagic shock. Renal artery was cannulated on one side via a percutaneous catheter opposite kidney served as control. Ureters were stented to measure urine output (UO). 3 animals in the late group (LCj were perfused after 1 hour of shock. Following 4 animals in the early group (EC) were perfused within 15 minutes of shock induction. Antegrade perfusion of the kidney was performed using a roller pump at perfusion pressures between 100-1 60 mm Hg using venous blood. Summarize Results: In shock, mean arterial pressure (MAP) was 57.6 2 1.9 mm Hg, mean venous saturation 46.6 26.5 "/o and mean U O 17 2 5.3 YO of the baseline. All perfused kidneys demonstrated recovery of renal function while contro kidneys remained anuric. In perfused kidneys, in spite of higher oxygen delivery (709.5 i 157.0 ml/min Vs 414.0 2 132.0 ml/min, p=0.0081 and higher renal blood flow (1 19 2 14 ml/min Vs 103 If: 38 ml/min, p=0.15) in the LC, U O (98.5 2 20.5 % Vs 39.4 2 lY.3 ' YO of haseline, p<0.001) and CFR (38 2 4 % Vs 24 t 12 % of baseline, p=0.56) were higher in the EC. Conclusion: Early perfusion of kidneys with venous blood provides significantly improved renal function.

ASAIO Journal, 2002

Acute renal failure (ARF) is a major determinant of morbidity and mortality in heart failure. Ear... more Acute renal failure (ARF) is a major determinant of morbidity and mortality in heart failure. Early direct perfusion of the kidney with venous hlood may improve renal function. Methods Used To determine the impact of early Vs late perfusion on renal function, ARF was created in 7 dogs by inducing hemorrhagic shock. Renal artery was cannulated on one side via a percutaneous catheter opposite kidney served as control. Ureters were stented to measure urine output (UO). 3 animals in the late group (LCj were perfused after 1 hour of shock. Following 4 animals in the early group (EC) were perfused within 15 minutes of shock induction. Antegrade perfusion of the kidney was performed using a roller pump at perfusion pressures between 100-1 60 mm Hg using venous blood. Summarize Results: In shock, mean arterial pressure (MAP) was 57.6 2 1.9 mm Hg, mean venous saturation 46.6 26.5 "/o and mean U O 17 2 5.3 YO of the baseline. All perfused kidneys demonstrated recovery of renal function while contro kidneys remained anuric. In perfused kidneys, in spite of higher oxygen delivery (709.5 i 157.0 ml/min Vs 414.0 2 132.0 ml/min, p=0.0081 and higher renal blood flow (1 19 2 14 ml/min Vs 103 If: 38 ml/min, p=0.15) in the LC, U O (98.5 2 20.5 % Vs 39.4 2 lY.3 ' YO of haseline, p<0.001) and CFR (38 2 4 % Vs 24 t 12 % of baseline, p=0.56) were higher in the EC. Conclusion: Early perfusion of kidneys with venous blood provides significantly improved renal function.

ASAIO Journal, 2001

ABSTRACT An abstract is unavailable. This article is available as HTML full text and PDF.