Brunston R L, Tao W, Bidani A, Cardenas V J, Traber D L, Zwischenberger J B
Department of Surgery, University of Texas Medical Branch, Galveston 77555-0528, USA.
ASAIO J. 1996 Sep-Oct;42(5):M845-9. doi: 10.1097/00002480-199609000-00110.
Arteriovenous carbon dioxide removal (AVCO2R) has been shown to achieve total carbon dioxide (CO2) exchange. To determine optimal blood and gas flow parameters that can provide maximal gas exchange and evaluate the utility of AVCO2R at reduced blood flow, the authors used a low resistance membrane gas exchanger within an arteriovenous shunt in mechanically ventilated sheep. Adult female sheep (n = 5) were anesthetized and underwent placement of the gas exchange device in a simple arteriovenous shunt created between the carotid artery and common jugular vein. CO2 removal was determined as the product of the sweep gas flow (100% oxygen) and its exhaust CO2 content. Gas and blood flow were varied independently, and incremental reductions in minute ventilation (MV) were made while maintaining normocapnia. At maximally reduced ventilator settings, stepwise reductions in blood flow were made to determine the resultant changes in arterial PaCO2 at a sweep gas flow of 3 L/min. CO2 removal increased proportionally to blood flow to a maximum of 1,417 +/- 26 ml/min (19% of cardiac output) and gas flow to 3 L/min. Normal PaO2 and PaCO2 could be maintained with minimal ventilator support (MV = 16% baseline MV) at a blood flow of 500 ml/min or higher. At these maximally reduced ventilator settings, moderate hypercapnia (PaCO2 < or = 75 mmHg) resulted only when blood flow was decreased to below 500 ml/min. Optimizing AVCO2R blood and gas flow maximizes CO2 removal and allows a significant reduction in minute ventilation. In cases of severely limited blood flow, lung rest can still be realized at moderate hypercapnia. At flow rates achievable by percutaneous access, extracorporeal AVCO2R can be used to achieve lung rest during mechanical ventilation.
动静脉二氧化碳清除（AVCO2R）已被证明可实现全二氧化碳（CO2）交换。为了确定能够提供最大气体交换的最佳血流和气体流量参数，并评估在血流减少时AVCO2R的效用，作者在机械通气的绵羊的动静脉分流中使用了低阻力膜式气体交换器。成年雌性绵羊（n = 5）接受麻醉，并在颈动脉和颈总静脉之间建立的简单动静脉分流中放置气体交换装置。CO2清除量被确定为吹扫气体流量（100%氧气）与其排出的CO2含量的乘积。气体和血流独立变化，在维持正常碳酸血症的同时逐步减少分钟通气量（MV）。在最大程度降低呼吸机设置时，逐步减少血流，以确定在3 L/min的吹扫气体流量下动脉血二氧化碳分压（PaCO2）的相应变化。CO2清除量与血流成比例增加，最高可达1417±26 ml/min（心输出量的19%），气体流量增加到3 L/min。在血流为500 ml/min或更高时，使用最小的呼吸机支持（MV = 基线MV的16%）即可维持正常的动脉血氧分压（PaO2）和PaCO2。在这些最大程度降低的呼吸机设置下，只有当血流降至500 ml/min以下时才会导致中度高碳酸血症（PaCO2≤75 mmHg）。优化AVCO2R的血流和气体流量可使CO2清除最大化，并显著减少分钟通气量。在血流严重受限的情况下，在中度高碳酸血症时仍可实现肺休息。在经皮通路可达到的流速下，体外AVCO2R可用于在机械通气期间实现肺休息。
