ASAIO journal : a peer-reviewed journal of the American Society for Artificial Internal Organs
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Experimental and clinical use of the intravascular oxygenator (IVOX), an intravenacaval gas exchange device, in acute respiratory failure yielded a CO2 transfer of 40-70 ml/min (approximately 30% of adult CO2 production) at normocapnia. Although significant, this rate of CO2 removal is not clinically useful. To maximize CO2 transfer, given the same gas exchange properties and structure design of the IVOX, the authors analyzed the effects of permissive hypercapnia (stepwise increase in arterial blood pCO2 up to 100 mmHg) and active blood mixing (with an intraaortic balloon pump) on different sizes of IVOX (sizes 7, 8, and 9 mm, surface area 0.21, 0.32, and 0.41 m2, respectively) using a previously established ex vivo circuit to model the human vena cava. ⋯ A 0.42 m2 surface area is associated with an O2 transfer of 80 ml/min without and 107 ml/min with active blood mixing. It is concluded that CO2 removal by IVOX alone is limited by insufficient surface area and the resistance in the blood-surface boundary layer. The combination of permissive hypercapnia, adequate blood flow, and active blood mixing can substantially improve CO2 removal and can therefore achieve clinically significant CO2 removal by intravenacaval gas exchange devices during severe respiratory failure.
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Uncontrollable hemorrhage accounts for a large proportion of total mortality in both civilian (31%) and military (47%) trauma victims. Hypothermia is a relatively safe method that could provide total body protection during hypovolemic shock and facilitate surgical intervention as a potentially life-saving procedure. This study tested the hypothesis that profound hypothermia and complete blood replacement in an established canine model, would facilitate resuscitative therapy from exsanguinating hypovolemic shock. ⋯ During rewarming the animals were autotransfused, weaned from the pump, and allowed to recover. All dogs (n = 8) survived, all but one with complete neurologic recovery: blood chemistry samples examined immediately after the procedure showed significant differences (p < 0.05) in only a few parameters, including creatine kinase (CK-BB and CK-MB), compared with the previous group of control dogs. The consistent survival of dogs showing apparently normal neurologic, physiologic, and biochemical recovery supports the concept that profound hypothermia using a protective hypothermic blood substitute could provide time for therapeutic resuscitation of currently intractable trauma cases.
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To overcome problems derived from the shaft within conventional centrifugal pumps, we have developed a new centrifugal pump, the magnetically suspended centrifugal pump (MSCP), which has no shaft and operates as a bearingless centrifugal pump. The impeller is suspended freely and centrally by magnetic force within the pump. Hemolysis tests were performed in comparison with the Biopump. ⋯ In the other sheep, the MSCP ran for 15 days, and showed no thrombus on the impeller. During each experiment, plasma free hemoglobin levels were less than 15 mg/dl. The MSCP induced less hemolysis than did the Biopump, and the MSCP containing an impeller coated with silicone demonstrated the potential to run for 14 days without thrombus formation within the pump.
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Recent experimental studies have suggested that the initial nonstimulated stage of dynamic cardiomyoplasty acutely impairs ventricular function. Those investigations were performed on normal hearts and primarily examined diastolic alterations as a result of the passive muscle wrap. The purpose of this study was to assess the acute systolic and diastolic effects of a nonstimulated muscle wrap in chronic heart failure induced by rapid ventricular pacing in canines. ⋯ By the end of the pacing period and before wrap, left ventricular dysfunction developed in all dogs, manifested by significant deterioration of both systolic and diastolic indices of ventricular function, as well as progressive increases in left ventricular volumes. However, no further deterioration with load insensitive indices of systolic or diastolic indicators of ventricular function was found as a result of the passive muscle wrap. These results suggest that the cardiomyoplasty procedure can be safely performed on failing hearts without prohibitive acute impairment of ventricular function.
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Advances in medical science and, in particular, minimally invasive surgical and diagnostic procedures have stimulated the development of new and improved medical devices. This has been made possible because of developments in engineering and material sciences. The design of devices for reusability is particularly important in an effort to provide cost effective healthcare. ⋯ The user needs to balance cost versus convenience and reprocessing requirements for reusables. Current trends are to reuse more devices, including many of which were meant to be disposable. Cost effective designs can best be achieved when the user and manufacturer work together on the design.(ABSTRACT TRUNCATED AT 250 WORDS)