A mathematical model of CO2, O2 and N2 exchange during venovenous extracorporeal membrane oxygenation

Joyce, Chris; Shekar, Kiran; Cook, David

doi:10.1186/s40635-018-0183-4

Cited by 11 publications

(24 citation statements)

References 25 publications

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“…8-10 , [20][21][22][23] To gain further increases in CO 2 clearance, an increase in blood flow is required. 7 , [24][25][26] In this study, we only tested the effects of gas flow on CO 2 exchange through the membrane for a period of 6 hours. In this context, our assessment of dead space was functional and related to the efficiency of the membrane.…”

Section: Discussionmentioning

confidence: 99%

“…8–10,20–23 To gain further increases in CO 2 clearance, an increase in blood flow is required. 7,24–26…”

Section: Discussionmentioning

confidence: 99%

“…The experiment was performed in only one low-flow system, 0.59m 2 membrane surface area device and results cannot be extrapolated to different devices with different surface areas or blood flow; however, the results are in keeping with results from other studies exploring these devices. 7,8,24–26 It is also acknowledged that although the haemoglobin used in the bench tests is in keeping with the current British Society of Haematology recommendations for red cell transfusion in critical illness, that there is a spectrum of haemoglobin targets used internationally in clinical practice and that this target does not reflect the full range of clinical practice internationally. Further limitations include the fact that only one circuit was able to be set up and only one set of blood gases at sweep gas flow rate was used in the analysis.…”

Section: Discussionmentioning

confidence: 99%

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In-vitro performance of a low flow extracorporeal carbon dioxide removal circuit

2019

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Introduction: Extracorporeal gas exchange requires the passage of oxygen and carbon dioxide (CO2) across an artificial membrane. Current European Union regulations do not require the transfer to be assessed in models using clinically relevant haemoglobin, making it difficult for clinicians to understand the CO2 clearance of a membrane, and how it changes in relation to sweep gas flow through the membrane. The characteristics of membrane CO2 clearance are described using a single membrane at different sweep gas flows in an in vitro model with clinically relevant haemoglobin concentrations using three separate methods of calculating CO2 clearance. Methods: To define the CO2 removal characteristics of the extra-corporeal CO2 removal (ECCO2R) device, we devised an in-vitro gas exchange circuit formed by a dedicated ECCO2R circuit (ALung, Pittsburgh, USA) in series with two membrane oxygenators. The system was primed with donated expired human red cells provided by the local blood bank. The experimental set-up allowed constant CO2 input (via one membrane oxygenator) with variable removal from a portion of the blood in a manner which was analogous to that seen in vivo. Blood gases were measured from different ports in the circuit in order to measure the experimental membrane CO2 clearance (VCO2). Results: Results demonstrate that the relationship between VCO2 and gas flow at a constant blood flow of 0.4 L/minute with a haemoglobin of 7 g/dL increases sharply from a gas flow of 0 to 2 L/min but plateaus at gas flows >4 L/minute. VCO2, calculated using three different methods, showed a strong linear correlation with minimal bias. Conclusions: The CO2 clearance of the membrane used in this bench test is non-linear. This has implications for clinical practice, especially during the weaning phase of the device.

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Section: Discussionmentioning

confidence: 99%

“…8–10,20–23 To gain further increases in CO 2 clearance, an increase in blood flow is required. 7,24–26…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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In-vitro performance of a low flow extracorporeal carbon dioxide removal circuit

2019

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“…Blood gas analysis was performed with an ABL 800, Radiometer, (Copenhagen, Denmark) with separate measurement for haemoglobin. Extracorporeal CO 2 removal was calculated as reported in detail in previous studies [ 18 , 24 , 25 ]. Of note, to compare the amount of CO 2 removal at different pre-membrane PCO 2 levels, the extracorporeal CO 2 removal was normalized to a PCO 2 of 45 mmHg.…”

Section: Methodsmentioning

confidence: 99%

Impact of sweep gas flow on extracorporeal CO2 removal (ECCO2R)

Straßmann

Merten

Schäfer

et al. 2019

ICMx

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BackgroundVeno-venous extracorporeal carbon dioxide (CO2) removal (vv-ECCO2R) is increasingly being used in the setting of acute respiratory failure. Blood flow rates range in clinical practice from 200 mL/min to more than 1500 mL/min, and sweep gas flow rates range from less than 1 to more than 10 L/min. The present porcine model study was aimed at determining the impact of varying sweep gas flow rates on CO2 removal under different blood flow conditions and membrane lung surface areas.MethodsTwo different membrane lungs, with surface areas of 0.4 and 0.8m2, were used in nine pigs with experimentally-induced hypercapnia. During each experiment, the blood flow was increased stepwise from 300 to 900 mL/min, with further increases up to 1800 mL/min with the larger membrane lung in steps of 300 mL/min. Sweep gas was titrated under each condition from 2 to 8 L/min in steps of 2 L/min. Extracorporeal CO2 elimination was normalized to a PaCO2 of 45 mmHg before the membrane lung.ResultsReversal of hypercapnia was only feasible when blood flow rates above 900 mL/min were used with a membrane lung surface area of at least 0.8m2. The membrane lung with a surface of 0.4m2 allowed a maximum normalized CO2 elimination rate of 41 ± 6 mL/min with 8 L/min sweep gas flow and 900 mL blood flow/min. The increase in sweep gas flow from 2 to 8 L/min increased normalized CO2 elimination from 35 ± 5 to 41 ± 6 with 900 mL blood flow/min, whereas with lower blood flow rates, any increase was less effective, levelling out at 4 L sweep gas flow/min. The membrane lung with a surface area of 0.8m2 allowed a maximum normalized CO2 elimination rate of 101 ± 12 mL/min with increasing influence of sweep gas flow. The delta of normalized CO2 elimination increased from 4 ± 2 to 26 ± 7 mL/min with blood flow rates being increased from 300 to 1800 mL/min, respectively.ConclusionsThe influence of sweep gas flow on the CO2 removal capacity of ECCO2R systems depends predominantly on blood flow rate and membrane lung surface area. In this model, considerable CO2 removal occurred only with the larger membrane lung surface of 0.8m2 and when blood flow rates of ≥ 900 mL/min were used.

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“…Moreover, specific phenomenon that might reduce device efficiency in vivo such as recirculation have also not been included in the current model. Our model is comparable in overall complexity to that recently described for extracorporeal membrane oxygenation …”

Section: Discussionmentioning

confidence: 90%

Extracorporeal carbon dioxide removal requirements for ultraprotective mechanical ventilation: Mathematical model predictions

et al. 2019

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A mathematical model of CO2, O2 and N2 exchange during venovenous extracorporeal membrane oxygenation

Cited by 11 publications

References 25 publications

In-vitro performance of a low flow extracorporeal carbon dioxide removal circuit

In-vitro performance of a low flow extracorporeal carbon dioxide removal circuit

Impact of sweep gas flow on extracorporeal CO2 removal (ECCO2R)

Extracorporeal carbon dioxide removal requirements for ultraprotective mechanical ventilation: Mathematical model predictions

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