Showing papers by "Robert H. Bartlett published in 2008"

Current status of extracorporeal membrane oxygenation for severe respiratory failure.

Abstract: Extracorporeal membrane oxygenation (ECMO) for respiratory failure was reviewed. ECMO progressed from laboratory research to initial clinical trials in 1972. Following a decade of clinical research, ECMO is now standard treatment for neonatal respiratory failure refractory to conventional pulmonary support techniques worldwide. The application of neonatal ECMO has been extended with improved outcome to premature and low birth weight infants as well as older children and adults. As of July 1994, 9,258 neonates, 754 pediatric, and 130 adult patients with respiratory failure treated with ECMO were entered in the registry of the Extracorporeal Life Support Organization (ELSO). Overall survival rates were 81% in neonates, 49% in pediatric, and 38% in adult patients. Recently the adult and pediatric populations treated with ECMO have increased rapidly, and the outcome has improved significantly.

Large animal model of chronic pulmonary hypertension.

Abstract: A large animal model is needed to study artificial lung attachment in a setting simulating chronic lung disease with significant pulmonary hypertension (PH). This study sought to create a sheep model that develops significant PH within 60 days with a low rate of mortality. Sephadex beads were injected in the pulmonary circulation of sheep every other day for 60 days at doses of 0.5, 0.75, and 1 g (n = 10, 10, 7). Mean pulmonary artery pressure, pulmonary capillary wedge pressure, and cardiac output were obtained every 2 weeks. In the 0.5, 0.75, and 1-g groups, 90, 70, and 14.3% of sheep completed the study, respectively, with the remainder experiencing heart failure. By the 60th day, pulmonary vascular resistance had increased (p < 0.01) from 0.89 +/- 0.3 to 3.2 +/- 0.9 mm Hg/(L/min) and from 0.9 +/- 0.3 to 4.3 +/- 3.2 mm Hg/(L/min) in the 0.5 and 0.75-g groups, respectively. Significant right ventricular hypertrophy was observed in the 0.75-g group but not in the 0.5-g group. Data from the 1-g group were insufficient for analysis due to high mortality. Thus, the 0.5 and 0.75-g groups generate significant PH, but the 0.75-g group is a better model of chronic PH in lung disease due to the development of right ventricular hypertrophy.

A polymethylpentene fiber gas exchanger for long-term extracorporeal life support (ASAIO Journal (2005) 51, (390-397))

Abstract: A polymethylpentene (PMP) fiber gas exchange device was evaluated in healthy sheep (35–42 kg) to characterize its performance and potential use in clinical extracorporeal life support (ECLS). Five PMP devices (1.3 m2) were compared with five silicone rubber membrane lung (SRML) devices (1.5 m2) that were supported on venovenous ECLS for 72 hours. The two device groups were compared for differences in gas exchange, device pressure gradient, hematology, blood biochemistry, and pathology. The results showed superiority in the PMP devices in both oxygen and CO2 exchange when compared at similar blood flow rates. Platelet consumption and the device pressure gradient were significantly less when using the PMP device. The device pressure gradient across the PMP devices was <20 mm Hg as compared with >150 mm Hg for the SRML devices at all blood flow rates. Changes in plasma hemoglobin levels, leukocyte counts, blood chemistry results, and pathologic findings were not significantly different between the two device groups. Plasma leakage or device failure did not occur in any of the test devices. These data support the use of the PMP device for extended circulatory support. Patients may fare better because of improved preservation of platelets, and the low resistance may allow for wider use of centrifugal-style pumps or the use of the device in a pumpless arteriovenous mode.

Pulsatile Flow Past Multiple Cylinders: A Model Study of Blood Flow in an Artificial Lung

Abstract: Pulsatile flow across two circular cylinders with different geometric arrangements is studied experimentally using particle image velocimetry method and numerically using the finite element method. This investigation is motivated by optimizing the design of a total artificial lung (TAL), a potential bridge to lung transplantation. Blood flow through the TAL is generated entirely by the right ventricle of the heart and no external pump is utilized, thus blood flow inside the TAL is pulsatile. The oxygen-poor blood flows across a bundle of hollow fibers that oxygen-rich air flows through. Understanding time-dependent flow around these fibers is crucial for optimizing design since convection is the dominant transport mechanism in the bulk blood flow. The vortex structures resulting from three different arrangements of cylinders (tandem, side-by-side, staggered) in pulsatile flow with Reynolds numbers of 1, 3, and 5 and Stokes numbers of 0.18 and 0.37 were investigated. Consistent results were observed in the numerical and experimental results. These results reveal that the vortex structure depends strongly on the geometric arrangement of the cylinders. The vortex strength is highly dependent on the Reynolds and Stokes numbers. These findings suggest design criteria for enhancing mixing and reducing pressure drop across the TAL.