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At least 19 recordsLinked to original sources
PubMed1976

Control, monitor and alarm system for clinical application of a membrane oxygenator.

Membrane oxygenators, now commercially available, are undergoing clinical trials as long-term (days) respiratory support devices for patients in potentially reversible respiratory failure. However, these devices must be used in an integrated system of controls, monitors and alarms if they are to be reliable and easy to operate in the clinical environment. This paper describes such a system. The tubing circuits for blood and for oxygen are described first. Next, details of the blood pump controls are presented. The system features servo control of pump speed to match blood inflow, and deactivation of the pump in the case of excessive output pressure. Gas circuit controls are described which allow the independent adjustment of both oxygen flow through the gas phase of the membrane lung and oxygen pressure developed at the inlet gas port. Audible alarms are provided for low blood inflow to the system, excessive blood outflow pressure, changes in oxygen flow and failure of the electric power supply to the system. In addition to pressure and flow monitors in the blood and gas circuits, blood oxygen saturation is continuously monitored at both input and output of the system. The membrane oxygenator system has proved to be reliable and easy to operate in both animal and human long-term perfusions.

Animals↗
PubMedDate not supplied

Scanning-electron-microscopic and functional studies of oxygenator-membranes during long-term-perfusion.

Various types and amount of deposits were noted on the surface of different membrane oxygenators during experimental long-term perfusion in sheep studied by SEM. They were present in spite of adequate heparinization. The deposition of blood material suggests, that the imperfection of the membranes by fabrication must be controlled and improved by oneself for use in long-term perfusion.

Animals↗
PubMed1979

Biocompatibility of standard and silica-free silicone rubber membrane oxygenators.

Spiral coil membrane oxygenators made from either standard silicone rubber or silica-free silicone rubber were compared using three priming techniques. Standard priming, carbon dioxide priming, and denucleation priming were employed with each type of device. Four-hour venovenous membrane oxygenator perfusions were carried out on awake sheep anticoagulated with heparin. Virtually no differences were observed in any parameters measured between standard silicone rubber and filler-free silicone rubber membranes. Significantly greater platelet losses occurred during the first hour of perfusion with standard priming and with carbon dioxide priming than with denucleation priming, using either type of membrane. These experiments demonstrate that denucleation priming reduces platelet losses during extracorporeal membrane oxygenator perfusion, but that the use of filler-free silicone rubber does not improve the biocompatibility of the membrane.

Animals↗
PubMed1977

Respiratory characteristics of a microporous membrane oxygenator.

A microporous membrane oxygenator has been used in 258 clinical perfusions for cardiac surgery. In 132 perfusions the oxygenator was ventilated with 100% O2, and in 126 perfusions 98% O2-2%CO2 was used. Patients' BSA was 0.4-2.3 M2. Bypass duration was up to 563 min. In the group ventilated with 100% O2, average PaCO2 was 30 mmHg, with arterial pH of 7.48. 98% O2-2% ventilation resulted in an average PaCO2 of 36 mmHg, with arterial pH of 7.41. CO2 transfer is influenced by gas flow rate, and data from selected cases demonstrate that increasing gas flow results in decreasing PaCO2, while decreasing gas flow increases PaCO2. The thickness of the blood film is decreased by increasing the "shim" pressure, so that increasing the "shim" presure results in higher PaO2. Oxygen saturation averaged 99% for the entire series. Addition of CO2 to the oxygen and appropriate changes in gas flow and "shim" pressure permit changes to be made in the ventilation of the device during perfusion to achieve desired levels of PaO2 and PaCO2 under widely disparate conditions of temperature and flow.

Adolescent↗
PubMed1992

Decreasing transfusion exposure risk during extracorporeal membrane oxygenation (ECMO).

Extracorporeal membrane oxygenation (ECMO) is a lifesaving therapy for neonatal pulmonary hypertension but carries a significant risk for transfusion-related complications. Packed red blood cell (PRBC) and platelet exposure were quantified and reviewed in 17 ECMO survivors prior (Group I, n = 9) and subsequent to (Group II, n = 8) changes in transfusion protocols. Blood product requirements included ECMO circuit priming, maintenance of haematocrit > 0.40 or platelet count > 50 x 10(9)/l, and colloid volume expansion. Group I was exposed to 13.8 +/- 10.2 (x +/- SD) different PRBC units. In Group II, multiple transfusions from single donor units decreased exposure 71% to 3.9 +/- 0.7 units (P < 0.05). Decreases in blood withdrawn (11%) and transfusion volume (7%) were coincident with a 15% reduction in mean bypass time. Platelet volume transfusion decreased from 159 +/- 213 to 93 +/- 64 ml using volume-reduced platelet packs. Total transfusion exposure decreased 59% from 20.8 +/- 17.8 units to 8.6 +/- 2.4 donor units. No transfusion complications occurred during the aggregate 1,926 h on bypass. We conclude that neonates on ECMO have a significant transfusion exposure risk increasing with prolonged duration of ECMO therapy. In addition we noted that concentrated platelet packs decreased transfusion volume by 41%, and multiple PRBC transfusions from single donor units decreased donor exposure by 71% while both strategies decreased the overall transfusion exposure risk by 59%.

Blood Component Transfusion↗
PubMed1979

Thrombus formation and microaggregate removal during extracorporeal membrane oxygenation.

Contemporary microporous membrane oxygenators have adequate gas transfer capacity and even prolonged oxygenation is relatively atraumatic to the blood elements. However, even with adequate heparinization, thrombus formation still takes place, albeit to a lesser degree than in direct blood-gas contact devices. In this work, scanning electron microscopy of the dissected devices in the extracorporeal circuit was performed on devices used during four aorto-coronary bypasses and two cardiac valve replacements. Membrane surfaces remained free of major deposits although thrombotic material could still be observed in parts of the oxygenators and the filters. Blood filtration from the cardiotomy reservoir may be more critical as it removes surgical debris and cells injured by suction which appear to enhance thrombus formation within the oxygenator. The return line arterial filter appears more useful as a bubble remover; its value appears much diminished as microemboli do not leave the device in large quantities.

Blood Cells↗
PubMed1978

Mathematical and experimental methods for design and evaluation of membrane oxygenators.

Three categories of membrane oxygenators are considered: passive flow, secondary flow induced by the mainstream, secondary flow induced by an external application of energy. The current status of mathematical methods for analysis of fluid mechanics, O2 and CO2 exchange for these categories are briefly reviewed. Emphasis is given to approximate methods for calculation of gas exchange. Practical methods for experimental design optimization studies are outlined; these methods are extended to evaluation of O2 and CO2 exchange in clinical operation. A new method for estimation of internal ventilation and perfusion maldistribution and diffusion resistance is described. A brief assessment of blood damage in clinical application of the oxygenator is presented from the point of view of deterioration of gas exchange performance.

Blood Flow Velocity↗
PubMedDate not supplied

Clinical evaluation of a microporous membrane oxygenator.

1. The microporous membrane oxygenator has a maximum priming volume of 400 ml. and transfers up to 250 ml. of O2. 2. CO2 transfer is excessive when ventilating the oxygenator with 100% O2. CO2 should be added to the ventilating gas. 3. The oxygenator has performed satisfactorily in 90 cases of cardiac surgery with perfusion time up to nine hours. 4. Precautions are described to prevent possible accumulation of water vapor in the oxygenator.

Adolescent↗
PubMed1977

[Use of a membrane oxygenator in extracorporeal circulation in the child. Preliminary conclusions].

The comparison of two types of oxygenators, the bubble and membrane oxygenator, in cardiac surgery under ECC, in infants. The results were not subjected to a statistical study. However, it seems that the membrane oxygenator enables one to obtain a satisfactory hematosis in a simpler fashion (the addition of CO2 being avoided) than with the bubble oxygenator and leads to less hemolysis than the latter. In the cases of closed circuit ECC with recirculation, the use of the membrane oxygenator also gives greater security of manipulation of the blood mass.

Carbon Dioxide↗
PubMed1975

Prolonged perfusion with a membrane oxygenator in awake ponies.

Prolonged extracorporeal membrane oxygenation (PEMO) was performed in 6 adult ponies with the membrane oxygenator in vein-to-artery bypass circuit. A flow rate equal to 46 per cent of control cardiac output was diverted through the PEMO circuit of 10 to 24 hours. Three of the 6 ponies were perfused for at least 20 hours and developed no complications. Immediately following initiation of PEMO, left ventricular output decreased; however, in the interval between 6 and 24 hours, left ventricular output was increased above control levels. Aortic pressure and left ventricular work were markedly elevated during PEMO. Pulmonary ventilation and oxygen uptake also decreased initially but were elevated during later stages of bypass. Pulmonary compliance did not change, except in those studies in which problems were encountered with perfusion techniques. Hepatic glycolysis and hyperglycemia occurred and were more severe in ponies with catheter-produced thrombi. Marked diuresis, which could be attributed only partially to the hyperglycemia, was present throughout PEMO. Based on the minimal morphologic changes observed in the ponies, extracorporeal circulation diverting one half of the cardiac output through a membrane oxygenator can be safely performed for up to 24 hours.

Animals↗
PubMed1975

Miliary tuberculosis presenting as acute respiratory failure: treatment by membrane oxygenator and ventricle pump.

A 58-year-old woman with high fever, dyspnea, rapidly progressive hypoxemia and opacification of the lung fields presented the clinical picture of catastrophic respiratory failure. Extracorporeal support of oxygenation using a membrane oxygenator and a new ventricle pump was initially successful. At autopsy, miliary tuberculosis was found to be the cause of this "shock lung like" syndrome.

Assisted Circulation↗
PubMedDate not supplied

[Diffusion of oxygen and carbon dioxide in a stationary membrane oxygenator].

Univariate diffusion of oxygen and carbon dioxide through a selective membrane of a stationary membranous oxygenator (SMO) and moving blood film is considered. Through the use of a precise exponential approximation of the oxyhemoglobin dissociation curve [S (p)=1--ae-bp] a partial oxygen pressure distribution [p (x)] along the SMO membrane and a transcedental equation for estimating the value for partial pressure (pa) of the arterialized blood and the SMO efficiency with reference to oxygen have been obtained. A somewhat less exact logarithmic approximation of the summary blood oxygen concentration [C1=a1+b1ln(p--po)] enables it to arrive at an analytical expression for calculating the SMO efficiency with reference to oxygen in a positively definite form. On the other hand, by using logarithmic approximation of the summary carbon dioxide concentration proceeding from the partial CO2 pressure in the blood a partial CO2 pressure distribution along the membrane, as well as an analytical expression for estimating the SMO efficiency with reference to carbon dioxide could be obtained.

Carbon Dioxide↗
PubMed1979

Comparison of bubble and membrane oxygenators in short and long perfusions.

Eighty patients had cardiopulmonary bypass (CPB), half having short (109 +/- 11 minutes) perfusions and half having long (188 +/- 14 min) perfusions. Twenty patients in each group were perfused with bubble oxygenators (Bentley, Harvey, or Galen) and 20 with membrane oxygenators (Modulung or Teflo). Hemodilution to a hematocrit value of 22.5% +/- 1.4% and hypothermia to 28 degrees +/- 2 degrees C were used in all patients. Complete hemograms, sequential multiple analyzer 18 tests, coagulation profiles, blood gases and pH, three immunoglobulins, and two complement fraction proteins were sampled as follows: three times before perfusion, one to ten times during perfusion, 1 hour immediately after perfusion, and 4, 24, and 48 hours postoperatively. Data in concentration terms were compared statistically and reported as mean and standard error for each subset. Additionally, rates of gain or loss were calculated in terms of quantity per liter of blood pumped per minute. During perfusion for both duration sets, use of a membrane oxygenator resulted in greater pump flows (4.55 +/- 0.15 L/min versus 3.75 +/- 0.11 L/min), lower total peripheral resistances (1,125 +/- 63 dynes.sec.cm-5 versus 1,652 +/- 115 dynes.sec.cm-5), and greater urinary outputs (9.4 +/- 1.1 ml/min versus 2.2 +/- 0.6 ml/min) than in the bubble oxygenator subsets. Comparisons of measured and calculated data in the immediate postperfusion interval showed no differences between bubble and membrane oxygenator subsets for short perfusions. In long perfusions, the membrane subset had lower plasma hemoglobin and white cell concentrations and generation rates, smaller (3 to 8 1/2 times) losses of IgG, IgM, C3 and shed blood necessitating less transfusion, and greater C4 losses. The membrane oxygenator systems used were more complex and costly and offered no advantages for short perfusion in adults. In anticipated long perfusions or where bleeding may be a problem, a membrane oxygenator appears more efficacious than bubble systems. For perfusions of less than 2 hours, membrane oxygenators had no biochemical or hematologic advantage over the bubble devices used in this study.

Blood Cell Count↗
PubMedDate not supplied

[Dimethylpolysiloxane reinforced film in a membrane oxygenator].

With the purpose of diffuse membranous oxygenation of blood the possibility of employing a Soviet-made dimethylpolyxyloxane-reinforced film "Sigma" was investigated. The test-trials were carried out with a membranous oxygenator of the "Sandwich" type. In 15 acute tests on dogs a partial cardio-pulmonary pass-by shunting with oxygenation of the blood after the veno-venous or veno-arterial perfusion was performed. With the mass-exchange area of 1.15 m2 the oxygen transport in different tests varied within a range of 20-50 ml/min and depended upon the arterio-venous difference and the circulation rate. No disruptions in the elimination of carbon dioxide were in evidence. In the course of investigations the "Sigma" material was found to be strong, impermeable to liquids and is not subject to swelling following its long-term use.

Dimethylpolysiloxanes↗