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Computer Methods and Programs in... Sep 2021While previous in vitro studies showed divergent results concerning the influence of pulsatile blood flow on oxygen advection in oxygenators, no study was done to...
While previous in vitro studies showed divergent results concerning the influence of pulsatile blood flow on oxygen advection in oxygenators, no study was done to investigate the uncertainty affected by blood flow dynamics. The aim of this study is to utilize a computational fluid dynamics model to clarify the debate concerning the influence of pulsatile blood flow on the oxygen transport. The computer model is based on a validated 2D finite volume approach that predicts oxygen transfer in pulsatile blood flow passing through a 300-micron hollow-fiber membrane bundle with a length of 254 mm, a building block for an artificial lung device. In this study, the flow parameters include the steady Reynolds number (Re = 2, 5, 10 and 20), Womersley parameter (Wo = 0.29, 0.38 and 0.53) and sinusoidal amplitude (A = 0.25, 0.5 and 0.75). Specifically, the computer model is extended to verify, for the first time, the previously measured O transport that was observed to be hindered by pulsating flow in the Biolung, developed by Michigan Critical Care Consultants. A comprehensive analysis is carried out on computed profiles and fields of oxygen partial pressure (P) and oxygen saturation (S) as a function of Re, Wo and A. Based on the present results, we observe the positive and negative effects of pulsatile flow on P at different blood flow rates. Besides, the S variation is not much influenced by the pulsatile flow conditions investigated. While being consistent with a recent experimental study, the computed O volume flow rate is found to be increased at high blood flow rates operated with low frequency and high amplitude. Furthermore, the present study qualitatively explains that divergent outcomes reported in previous in vitro experimental studies could be owing to the different blood flow rates adopted. Finally, the contour analysis reveals how the spatial distributions of P and S vary over time.
Topics: Equipment Design; Humans; Hydrodynamics; Lung; Oxygen; Oxygenators, Membrane; Pulsatile Flow
PubMed: 34247118
DOI: 10.1016/j.cmpb.2021.106241 -
Circulation. Heart Failure Apr 2023Exposure to hyperoxia, a high arterial partial pressure of oxygen (PaO2), may be associated with worse outcomes in patients receiving extracorporeal membrane oxygenator...
BACKGROUND
Exposure to hyperoxia, a high arterial partial pressure of oxygen (PaO2), may be associated with worse outcomes in patients receiving extracorporeal membrane oxygenator (ECMO) support. We examined hyperoxia in the Extracorporeal Life Support Organization Registry among patients receiving venoarterial ECMO for cardiogenic shock.
METHODS
We included Extracorporeal Life Support Organization Registry patients from 2010 to 2020 who received venoarterial ECMO for cardiogenic shock, excluding extracorporeal CPR. Patients were grouped based on PaO2 after 24 hours of ECMO: normoxia (PaO2 60-150 mmHg), mild hyperoxia (PaO2 151-300 mmHg), and severe hyperoxia (PaO2 >300 mmHg). In-hospital mortality was evaluated using multivariable logistic regression.
RESULTS
Among 9959 patients, 3005 (30.2%) patients had mild hyperoxia and 1972 (19.8%) had severe hyperoxia. In-hospital mortality increased across groups: normoxia, 47.8%; mild hyperoxia, 55.6% (adjusted odds ratio, 1.37 [95% CI, 1.23-1.53]; <0.001); severe hyperoxia, 65.4% (adjusted odds ratio, 2.20 [95% CI, 1.92-2.52]; <0.001). A higher PaO2 was incrementally associated with increased in-hospital mortality (adjusted odds ratio, 1.14 per 50 mmHg higher [95% CI, 1.12-1.16]; <0.001). Patients with a higher PaO2 had increased in-hospital mortality in each subgroup and when stratified by ventilator settings, airway pressures, acid-base status, and other clinical variables. In the random forest model, PaO2 was the second strongest predictor of in-hospital mortality, after older age.
CONCLUSIONS
Exposure to hyperoxia during venoarterial ECMO support for cardiogenic shock is strongly associated with increased in-hospital mortality, independent from hemodynamic and ventilatory status. Until clinical trial data are available, we suggest targeting a normal PaO2 and avoiding hyperoxia in CS patients receiving venoarterial ECMO.
Topics: Humans; Shock, Cardiogenic; Hyperoxia; Oxygenators, Membrane; Heart Failure; Oxygen; Hospital Mortality; Hypertension; Retrospective Studies
PubMed: 36871240
DOI: 10.1161/CIRCHEARTFAILURE.122.010328 -
Monaldi Archives For Chest Disease =... Feb 1999Intravascular gas exchange, in which miniaturized hollow fibre oxygenators are inserted into the caval veins, has been proposed as a simpler and safer alternative to... (Review)
Review
Intravascular gas exchange, in which miniaturized hollow fibre oxygenators are inserted into the caval veins, has been proposed as a simpler and safer alternative to extracorporeal support in severe respiratory failure. One such device, the IVOX (intravascular oxygenator), has undergone clinical trials (160 implants) and, despite individual benefits, was found to be limited in its gas exchanging capacity. The peculiarities of oxygen physiology render pre-pulmonary oxygenation inefficient and variable, whereas carbon dioxide clearance is much more predictable. Several devices are currently undergoing development and may offer substantially enhanced gas exchange. The new devices, which may be several years from widespread clinical assessment, offer exciting therapeutic options in severe respiratory failure but are unlikely to completely replace extracorporeal techniques in the most severe forms of respiratory failure.
Topics: Equipment Design; Humans; Oxygen; Oxygenators, Membrane; Pulmonary Gas Exchange; Respiratory Insufficiency; Respiratory Therapy
PubMed: 10218369
DOI: No ID Found -
Archives of Surgery (Chicago, Ill. :... Aug 1975Since April 1973 we have treated nine patients with extracorporeal membrane oxygenation (ECMO), utilizing the spiral coil membrane lung. One patient is a long-term...
Since April 1973 we have treated nine patients with extracorporeal membrane oxygenation (ECMO), utilizing the spiral coil membrane lung. One patient is a long-term survivor. All patients except one showed substantial improvement in peripheral arterial oxygen tension. Four adults and two neonates were treated for critical hypoxia. Two patients were treated for cardiac failure but failed to show improved myocardial function. Complications involving perfusion circuitry, cannulation, chronic systemic heparinization, thrombocytopenia, and renal failure have been managed with minimal difficulty. However, irreversible pulmonary, neurologic, hepatic, or gastrointestinal damage due to hypoxia present before the institution of ECMO was associated with lethal complications. The ECMO has supplied adequate oxygenation to this group of nine critically hypoxic patients. Institution of ECMO at an earlier date in patients with critical hypoxia would provide a higher likelihood of survival.
Topics: Acute Kidney Injury; Adolescent; Adult; Blood Coagulation Disorders; Carbon Dioxide; Child, Preschool; Female; Femoral Vein; Gastrointestinal Hemorrhage; Heart Failure; Humans; Hypoxia; Infant, Newborn; Jugular Veins; Male; Middle Aged; Oxygen; Oxygenators, Membrane; Perfusion; Positive-Pressure Respiration; Pulmonary Edema; Respiratory Insufficiency; Vena Cava, Inferior; Vena Cava, Superior
PubMed: 1098613
DOI: 10.1001/archsurg.1975.01360140110022 -
Perfusion 1994Five infants with congenital heart disease were perfused with the D-901 neonatal oxygenator at the time of their cardiac surgery. The ability to reduce the prime volume...
Five infants with congenital heart disease were perfused with the D-901 neonatal oxygenator at the time of their cardiac surgery. The ability to reduce the prime volume below the blood volume as well as the blood handling and gas transfer characteristics were studied. In all cases the prime volume was less than or equal to the blood volume of the patient. This resulted in a reduction in the use of homologous blood products. Due to the concept of the D-901 it was possible to adapt the tubing in such a way that a complete prime of 220 ml was obtained. The device had a maximum oxygen transfer of 45 ml/min. The maximum carbon dioxide removal was 50 ml/min at a blood gas ratio of one. The mean platelet count post bypass decreased to 91% of the baseline value. Mean free haemoglobin levels increased to 86 mg/100 ml at 120 minutes of bypass. We conclude that the D-901 oxygenator opens new perspectives for perfusion in small babies in terms of priming volume and use of homologous blood products while maintaining good gas transfer characteristics. However, larger series are necessary to expand our experience with this device and its limitations. No specific problems related to the device were encountered and all infants had an uneventful postoperative course.
Topics: Blood Proteins; Hematocrit; Hemolysis; Humans; Infant, Newborn; Oxygen; Oxygenators; Platelet Count
PubMed: 7833543
DOI: 10.1177/026765919400900507 -
Interactive Cardiovascular and Thoracic... Sep 2015Oxygenation of blood and other physiological solutions are routinely required in fundamental research for both in vitro and in vivo experimentation. However, very few...
OBJECTIVES
Oxygenation of blood and other physiological solutions are routinely required in fundamental research for both in vitro and in vivo experimentation. However, very few oxygenators with suitable priming volumes (<2-3 ml) are available for surgery in small animals. We have designed a new, miniaturized membrane oxygenator and investigated the oxygen-transfer performance using both buffer and blood perfusates.
METHODS
The mini-oxygenator was designed with a central perforated core-tube surrounded by parallel-oriented microporous polypropylene hollow fibres, placed inside a hollow shell with a lateral-luer outlet, and sealed at both extremities. With this design, perfusate is delivered via the core-tube to the centre of the mini-oxygenator, and exits via the luer port. A series of mini-oxygenators were constructed and tested in an in vitro perfusion circuit by monitoring oxygen transfer using modified Krebs-Henseleit buffer or whole porcine blood. Effects of perfusion pressure and temperature over flows of 5-60 ml × min(-1) were assessed.
RESULTS
Twelve mini-oxygenators with a mean priming volume of 1.5 ± 0.3 ml were evaluated. With buffer, oxygen transfer reached a maximum of 14.8 ± 1.0 ml O2 × l(-1) (pO2: 450 ± 32 mmHg) at perfusate flow rates of 5 ml × min(-1) and decreased with an increase in perfusate flow to 7.8 ± 0.7 ml ml O2 × l(-1) (pO2: 219 ± 24 mmHg) at 60 ml × min(-1). Similarly, with blood perfusate, oxygen transfer also decreased as perfusate flow increased, ranging from 33 ± 5 ml O2 × l(-1) at 5 ml × min(-1) to 11 ± 2 ml O2 × l(-1) at 60 ml × min(-1). Furthermore, oxygen transfer capacity remained stable with blood perfusion over a period of at least 2 h.
CONCLUSIONS
We have developed a new miniaturized membrane oxygenator with an ultra-low priming volume (<2 ml) and adequate oxygenation performance. This oxygenator may be of use in overcoming current limitations in equipment size for effective oxygenation in low-volume perfusion circuits, such as small animal extracorporeal circulation and ex vivo organ perfusion.
Topics: Animals; Carbon Dioxide; Cardiac Surgical Procedures; Equipment Design; Extracorporeal Membrane Oxygenation; Heart Diseases; Miniaturization; Oxygen; Oxygenators, Membrane; Swine
PubMed: 26037378
DOI: 10.1093/icvts/ivv141 -
Plant & Cell Physiology Nov 2021Oxygen is essential for multicellular aerobic life due to its central role in energy metabolism. The availability of oxygen can drop below the level to sustain oxidative... (Review)
Review
Oxygen is essential for multicellular aerobic life due to its central role in energy metabolism. The availability of oxygen can drop below the level to sustain oxidative phosphorylation when plants are flooded, posing a severe threat to survival. However, under non-stressful conditions, the internal oxygen concentration of most plant tissue is not in equilibrium with the environment, which is attributed to cellular respiration and diffusion constrains imposed by O2 barriers and bulky tissue. This is exemplified by the observations of steep oxygen gradients in roots, fruits, tubers, anthers and meristems. To adapt to a varying availability of oxygen, plants sense O2 via the conditional proteolysis of transcriptional regulators. This mechanism acts to switch oxidative metabolism to anaerobic fermentation, but it was also shown to play a role in plant development and pathogen defense. To investigate how dynamic and spatial distribution of O2 impacts on these processes, accurate mapping of its concentration in plants is essential. Physical oxygen sensors have been employed for decades to profile internal oxygen concentrations in plants, while genetically encoded oxygen biosensors have only recently started to see use. Driven by the critical role of hypoxia in human pathology and development, several novel oxygen-sensing devices have also been characterized in cell lines and animal model organisms. This review aims to provide an overview of available oxygen biosensors and to discuss their potential application to image oxygen levels in plants.
Topics: Biosensing Techniques; Cell Respiration; Intravital Microscopy; Oxygen; Plant Cells
PubMed: 33725087
DOI: 10.1093/pcp/pcab039 -
ASAIO Journal (American Society For... Aug 2022Thrombosis in extracorporeal membrane oxygenation (ECMO) circuits remains a frequent complication. We characterize the location, extent, structure, and clinical...
Thrombosis in extracorporeal membrane oxygenation (ECMO) circuits remains a frequent complication. We characterize the location, extent, structure, and clinical implications of thrombi in 53 ECMO circuits from 46 pediatric patients. The tubing, pump, and oxygenator were examined for visible thrombi. Representative samples of thrombi were collected for histologic, immunofluorescence, and immunohistochemical analysis. Thrombi were found in 81% of ECMO circuits. The most clinically significant were inflow oxygenator membrane surface thrombi (11% of circuits), arterial tubing thrombi (30%), and venous tubing (26%) or connector thrombi (26%). Oxygenator membrane surface thrombi resulted in rapidly increasing delta pressure across the oxygenator over 1-2 days, oxygenator failure, and circuit replacement. Oxygenator membrane surface thrombi were associated with intravascular venous thrombosis and bacterial infection before starting ECMO. Arterial cannula/tubing thrombi led in one case to aortic and mesenteric artery thrombosis followed by bowel infarction. In 11% of cases, venous tubing thrombi grew large enough to break off and embolize to the pump, resulting in increased hemolysis. Antifibrinolytic therapy during ECMO was associated with an increased risk of pump thromboembolism. Other less clinically significant thrombi included pump axle thrombi with thrombus fragments trapped in the oxygenator (45%), and deep oxygenator membrane thrombi (15%). Examination of ECMO circuits after removal is a useful quality improvement tool that can elucidate the cause of circuit problems, indicate patients at increased risk of thrombosis, and suggest areas for possible improvements.
Topics: Child; Extracorporeal Membrane Oxygenation; Humans; Oxygenators; Oxygenators, Membrane; Thrombosis
PubMed: 34860711
DOI: 10.1097/MAT.0000000000001605 -
Free Radical Biology & Medicine Aug 2019For well over a hundred years, members of the bacterial phylum Cyanobacteria have been considered strictly photosynthetic microorganisms, reflected in their... (Review)
Review
For well over a hundred years, members of the bacterial phylum Cyanobacteria have been considered strictly photosynthetic microorganisms, reflected in their classification as "blue-green algae" in the botanical code. Recently, genomes recovered from environmental sequencing surveys representing two major uncultured basal lineages (classes) of Cyanobacteria have been found to completely lack photosynthetic and CO fixation genes. The most likely explanation for this finding is that oxygenic photosynthesis was not an ancestral feature of the Cyanobacteria, and rather originated following divergence of the primary lines of descent. Here we describe recent findings on the evolution of aerobic respiration in the non-photosynthetic cyanobacterial classes, and how this has been interpreted by researchers interested in the evolution of oxygenic photosynthesis.
Topics: Aerobiosis; Biological Evolution; Cell Respiration; Cyanobacteria; Oxygen; Photosynthesis
PubMed: 30930297
DOI: 10.1016/j.freeradbiomed.2019.03.029 -
Journal of Applied Physiology Jan 1965
Topics: Blood; Equipment and Supplies; Intestines; Kidney; Liver; Oxygen; Oxygenators; Perfusion; Rats; Research
PubMed: 14257548
DOI: 10.1152/jappl.1965.20.1.159