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Extracorporeal CO 2 removal by hemodialysis: in vitro model and feasibility

View Article: PubMed Central - PubMed

ABSTRACT

Background: Critically ill patients with acute respiratory distress syndrome and acute exacerbations of chronic obstructive pulmonary disease often develop hypercapnia and require mechanical ventilation. Extracorporeal carbon dioxide removal can manage hypercarbia by removing carbon dioxide directly from the bloodstream. Respiratory hemodialysis uses traditional hemodialysis to remove CO2 from the blood, mainly as bicarbonate. In this study, Stewart’s approach to acid-base chemistry was used to create a dialysate that would maintain blood pH while removing CO2 as well as determine the blood and dialysate flow rates necessary to remove clinically relevant CO2 volumes.

Methods: Bench studies were performed using a scaled down respiratory hemodialyzer in bovine or porcine blood. The scaling factor for the bench top experiments was 22.5. In vitro dialysate flow rates ranged from 2.2 to 24 mL/min (49.5–540 mL/min scaled up) and blood flow rates were set at 11 and 18.7 mL/min (248–421 mL/min scaled up). Blood inlet CO2 concentrations were set at 50 and 100 mmHg.

Results: Results are reported as scaled up values. The CO2 removal rate was highest at intermittent hemodialysis blood and dialysate flow rates. At an inlet pCO2 of 50 mmHg, the CO2 removal rate increased from 62.6 ± 4.8 to 77.7 ± 3 mL/min when the blood flow rate increased from 248 to 421 mL/min. At an inlet pCO2 of 100 mmHg, the device was able to remove up to 117.8 ± 3.8 mL/min of CO2. None of the test conditions caused the blood pH to decrease, and increases were ≤0.08.

Conclusions: When the bench top data is scaled up, the system removes a therapeutic amount of CO2 standard intermittent hemodialysis flow rates. The zero bicarbonate dialysate did not cause acidosis in the post-dialyzer blood. These results demonstrate that, with further development, respiratory hemodialysis can be a minimally invasive extracorporeal carbon dioxide removal treatment option.

No MeSH data available.


Schematic of the in vitro, single-pass CO2 removal setup. Blood was pumped through the inside of the dialyzer fibers while dialysate was independently pumped over the outside of the fibers. The oxygenator conditioned the blood, and blood samples were taken before and after the dialyzer
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Fig1: Schematic of the in vitro, single-pass CO2 removal setup. Blood was pumped through the inside of the dialyzer fibers while dialysate was independently pumped over the outside of the fibers. The oxygenator conditioned the blood, and blood samples were taken before and after the dialyzer

Mentions: Gas exchange was tested in a single-pass system (Fig. 1). The blood side of the system consisted of a 6-L reservoir bag, a Medtronic Affinity oxygenator (Medtronic, Minneapolis, MN) used to control inlet pCO2 and heat the blood to 37 °C, and a Gambro M10 dialyzer (Gambro, Lyon, Paris; surface area 0.04 m2). The dialysis side of the system consisted of a 6-L reservoir bag submerged in a 37 °C water bath. The zero bicarbonate dialysate used is previously described. Masterflex L/S roller pumps (Cole Palmer Instrument Co, Vernon Hills, IL) were used to control blood and dialysate flow rates.Fig. 1


Extracorporeal CO 2 removal by hemodialysis: in vitro model and feasibility
Schematic of the in vitro, single-pass CO2 removal setup. Blood was pumped through the inside of the dialyzer fibers while dialysate was independently pumped over the outside of the fibers. The oxygenator conditioned the blood, and blood samples were taken before and after the dialyzer
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383917&req=5

Fig1: Schematic of the in vitro, single-pass CO2 removal setup. Blood was pumped through the inside of the dialyzer fibers while dialysate was independently pumped over the outside of the fibers. The oxygenator conditioned the blood, and blood samples were taken before and after the dialyzer
Mentions: Gas exchange was tested in a single-pass system (Fig. 1). The blood side of the system consisted of a 6-L reservoir bag, a Medtronic Affinity oxygenator (Medtronic, Minneapolis, MN) used to control inlet pCO2 and heat the blood to 37 °C, and a Gambro M10 dialyzer (Gambro, Lyon, Paris; surface area 0.04 m2). The dialysis side of the system consisted of a 6-L reservoir bag submerged in a 37 °C water bath. The zero bicarbonate dialysate used is previously described. Masterflex L/S roller pumps (Cole Palmer Instrument Co, Vernon Hills, IL) were used to control blood and dialysate flow rates.Fig. 1

View Article: PubMed Central - PubMed

ABSTRACT

Background: Critically ill patients with acute respiratory distress syndrome and acute exacerbations of chronic obstructive pulmonary disease often develop hypercapnia and require mechanical ventilation. Extracorporeal carbon dioxide removal can manage hypercarbia by removing carbon dioxide directly from the bloodstream. Respiratory hemodialysis uses traditional hemodialysis to remove CO2 from the blood, mainly as bicarbonate. In this study, Stewart’s approach to acid-base chemistry was used to create a dialysate that would maintain blood pH while removing CO2 as well as determine the blood and dialysate flow rates necessary to remove clinically relevant CO2 volumes.

Methods: Bench studies were performed using a scaled down respiratory hemodialyzer in bovine or porcine blood. The scaling factor for the bench top experiments was 22.5. In vitro dialysate flow rates ranged from 2.2 to 24 mL/min (49.5–540 mL/min scaled up) and blood flow rates were set at 11 and 18.7 mL/min (248–421 mL/min scaled up). Blood inlet CO2 concentrations were set at 50 and 100 mmHg.

Results: Results are reported as scaled up values. The CO2 removal rate was highest at intermittent hemodialysis blood and dialysate flow rates. At an inlet pCO2 of 50 mmHg, the CO2 removal rate increased from 62.6 ± 4.8 to 77.7 ± 3 mL/min when the blood flow rate increased from 248 to 421 mL/min. At an inlet pCO2 of 100 mmHg, the device was able to remove up to 117.8 ± 3.8 mL/min of CO2. None of the test conditions caused the blood pH to decrease, and increases were ≤0.08.

Conclusions: When the bench top data is scaled up, the system removes a therapeutic amount of CO2 standard intermittent hemodialysis flow rates. The zero bicarbonate dialysate did not cause acidosis in the post-dialyzer blood. These results demonstrate that, with further development, respiratory hemodialysis can be a minimally invasive extracorporeal carbon dioxide removal treatment option.

No MeSH data available.