Supplementary Material for: Increased Longevity of a Novel Gas Exchanger System for Low-Flow Veno-Venous Extracorporeal CO<sub>2</sub> Removal in Acute Hypercapnic Respiratory Failure
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<b><i>Introduction:</i></b> Low-flow veno-venous extracorporeal CO<sub>2</sub> removal (ECCO<sub>2</sub>R) is an adjunctive therapy to support lung protective ventilation or maintain spontaneous breathing in hypercapnic respiratory failure. Low-flow ECCO<sub>2</sub>R is less invasive compared to higher flow systems, while potentially compromising efficiency and membrane lifetime. To counteract this shortcoming, a high-longevity system has recently been developed. Our hypotheses were that the novel membrane system provides runtimes up to 120 h, and CO<sub>2</sub> removal remains constant throughout membrane system lifetime. <b><i>Methods:</i></b> Seventy patients with pH ≤ 7.25 and/or PaCO<sub>2</sub> ≥9 kPa exceeding lung protective ventilation limits, or experiencing respiratory exhaustion during spontaneous breathing, were treated with the high-longevity ProLUNG system or in a control group using the original gas exchanger. Treatment parameters, gas exchanger runtime, and sweep-gas VCO<sub>2</sub> were recorded across 9,806 treatment-hours and retrospectively analyzed. <b><i>Results:</i></b> 25/33 and 23/37 patients were mechanically ventilated as opposed to awake spontaneously breathing in both groups. The high-longevity system increased gas exchanger runtime from 29 ± 16 to 48 ± 36 h in ventilated and from 22 ± 14 to 31 ± 31 h in awake patients (<i>p</i> < 0.0001), with longer runtime in the former (<i>p</i> < 0.01). VCO<sub>2</sub> remained constant at 86 ± 34 mL/min (<i>p</i> = 0.11). Overall, PaCO<sub>2</sub> decreased from 9.1 ± 2.0 to 7.9 ± 1.9 kPa within 1 h (<i>p</i> < 0.001). Tidal volume could be maintained at 5.4 ± 1.8 versus 5.7 ± 2.2 mL/kg at 120 h (<i>p</i> = 0.60), and peak airway pressure could be reduced from 31.1 ± 5.1 to 27.5 ± 6.8 mbar (<i>p</i> < 0.01). <b><i>Conclusion:</i></b> Using a high-longevity gas exchanger system, membrane lifetime in low-flow ECCO<sub>2</sub>R could be extended in comparison to previous systems but remained below 120 h, especially in spontaneously breathing patients. Extracorporeal VCO<sub>2</sub> remained constant throughout gas exchanger system runtime and was consistent with removal of approximately 50% of expected CO<sub>2</sub> production, enabling lung protective ventilation despite hypercapnic respiratory failure.
**引言：** 低流量静脉-静脉体外CO₂清除术（low-flow veno-venous extracorporeal CO₂ removal, ECCO₂R）是一种辅助治疗手段，用于在高碳酸血症性呼吸衰竭患者中支持肺保护性通气或维持自主呼吸。相较于高流量系统，低流量ECCO₂R的侵入性更低，但可能会削弱清除效率并缩短膜式气体交换器的使用寿命。为克服这一缺陷，近期研发出了一种高使用寿命系统。本研究的假设为：新型膜式系统的运行时长可达120小时，且在整个膜式系统使用寿命期间，CO₂清除率保持稳定。 **方法：** 本研究纳入70例患者，其动脉血二氧化碳分压（partial pressure of arterial carbon dioxide, PaCO₂）≥9 kPa且超出肺保护性通气限值，或在自主呼吸过程中出现呼吸耗竭，将其分为两组：一组接受高使用寿命ProLUNG系统治疗，另一组为对照组，采用原始气体交换器进行治疗。研究人员共记录了9806个治疗小时的治疗参数、气体交换器运行时长以及扫气流CO₂排出量（volumetric CO₂ elimination, VCO₂），并进行了回顾性分析。 **结果：** 两组分别有25/33例与23/37例患者接受机械通气，其余患者维持自主清醒呼吸状态。高使用寿命系统可将机械通气患者的气体交换器运行时长从29±16小时提升至48±36小时，将清醒自主呼吸患者的运行时长从22±14小时提升至31±31小时（P<0.0001）；且机械通气患者的运行时长更长（P<0.01）。VCO₂稳定维持在86±34 mL/min（P=0.11）。整体而言，患者的PaCO₂在1小时内从9.1±2.0 kPa降至7.9±1.9 kPa（P<0.001）。在120小时时，两组潮气量（tidal volume）分别可维持在5.4±1.8与5.7±2.2 mL/kg（P=0.60），而气道峰压可从31.1±5.1 mbar降至27.5±6.8 mbar（P<0.01）。 **结论：** 采用高使用寿命气体交换器系统，相较于既往系统，低流量ECCO₂R的膜式交换器使用寿命得以延长，但仍未达到120小时，尤其在自主呼吸患者中表现更为明显。体外VCO₂在整个气体交换器系统运行期间保持稳定，且与预期CO₂产生量的约50%清除量相符，即便在高碳酸血症性呼吸衰竭患者中，也可实现肺保护性通气。
