Abstract: Ｏｂｊｅｃｔｉｖｅ：To investigate the efficiency and effective factors of a low-flow extracorporeal carbon dioxide removal （ECCO2R） device in a group of hypercapnia pigs.
Ｍｅｔｈｏｄｏｌｏｇｙ：Controlled by low tidal volume， 6 hypercapnia pigs were treated with extracorporeal carbon dioxide removal （ECCO2R） combined with continuous renal replacement therapy （CRRT）. During the first 2 hours， at the gas flow of 12 L／min， 2 membrane devices with the surface area of 0.8 m2 and 1.2 m2 were alternately applicated， adjustments were made every 15 minutes to measure the volume of CO2 removement （VCO2） at blood flow （BF） of 100 mL／min， 250 mL／min， and 400 mL／min. For the next 2 hours， a 0.8m2 area device and a BF of 400 mL／min were provided， and adjustments were also made every 15 minutes at gas flow of 4 L／min， 8 L／min， and 12 L／min. In the third 2 hours， with the 0.8 m2 area device and the gas flow of 12 L／min， adjusted the tidal volume to change the pre-membrane CO2 partial pressure （PCO2pre）， measuring the VCO2 at BF 100 mL／min， 250 mL／min， and 400 mL／min. Using the previous membrane device， with the BF 400 mL／min， gas flow 12 L／min and PCO2pre at 70 mmHg for the continuous 24-hour treatment， the changes of indicators in blood gas analysis were observed.
Ｒｅｓｕｌｔｓ：Five out of six pigs completed 24-hour treatment， one of them interrupted treatment due to severe coagulation of the membrane device. There is no difference in the adjusted VCO2 of two membrane devices with the same BF， VCO2 did not increased （P>0.05） as the gas flow increased. As BF or PCO2pre increased， VCO2 significantly increased， the relationship could be represented by the following equation: VCO2 （mL／min）=0.18×BF （mL／min）+1.21×PCO2pre（mmHg）-59.89 （P<0.000 1， conditional R2=0.82）. During continuous 24-hour treatment， VCO2 reached its maximum at baseline， 119.33±23.16ml／min， followed by a slowly decrease and gradually stabilizing at 60~70 ml／min. Partial pressure of arterial carbon dioxide （PaCO2） decreased to 48.36±5.02 mmHg from 59.22±5.22 mmHg after the first-hour， and the pH value increased from 7.30±0.05 to 7.39±0.02（P<0.05）. In the subsequent treatment， PaCO2 remained relatively stable， with a 24-hour value of 51.04±3.98 mmHg（P<0.05） and the pH value slightly decreased， reaching 7.34±0.03（P>0.05） at 24 hours.
Ｃｏｎｃｌｕｓｉｏｎ：The CO2 removal efficiency of low-flow ECCO2R is mainly related to BF and is also affected by blood PCO2. A membrane area of 0.8 m2 or 1.2 m2 and a gas flow rate of 4 to 12 L／min have no significant effect on CO2 removal efficiency. By utilizing the CRRT platform's low flow continuous ECCO2R， PaCO2can be effectively reduced.

Key words: hypercapnia, continuous renal replacement therapy, low blood flow, extracorporeal carbon dioxide removal