Disclaimer: This guideline describes the ECMO circuit for all patient populations. These guidelines describe safe practice based on extensive experience and are considered consensus guidelines. These guidelines are not intended to define standard of care and are revised at regular intervals as new information, devices, medications, and techniques become available.


The Extracorporeal Membrane Oxygenation (ECMO) circuit

The extracorporeal membrane oxygenation (ECMO) circuit is composed of three main components including a pump, oxygenator, and heat exchanger. Venous blood is drained and then pumped through the heating component (which is usually integrated in the oxygenator), the oxygenator, and then returned to the patient. The circuit blood is returned to an artery (venoarterial ECMO [VA ECMO]) or a vein (venovenous ECMO [VV ECMO]). Circuits can have multiple access ports added as needed. The benefit of circuit access ports is the ability to administer medications, perform continuous renal replacement therapy (CRRT) through the ECMO circuit, and offer additional monitoring capabilities. However, too many connectors and access points in the circuit can lead to blood stagnation and clot formation, as well to an accidental rupture or disconnection. Highly complex ECMO systems will require a more skilled and knowledgeable ECMO specialist (the technical specialist trained to manage the ECMO system and the clinical needs of the patient on ECMO under the direction and supervision of an ECMO trained physician [ELSO Guidelines for Cardiopulmonary Extracorporeal Life Support, 2019]) available at the bedside. An ECMO specialist should have a strong intensive care background in neonatal, pediatric, or adult critical care. (ELSO Red Book 5th Edition Ch 4).


Venoarterial or Venovenous Extracorporeal Membrane Oxygenation

VA ECMO is indicated in conditions of acute cardiac failure in which the heart is unable to maintain the perfusion and metabolic demands of the body. VA ECMO is used for respiratory support in neonates and some small children, also can be used for children and adults for concomitant respiratory and cardiac failure. (ELSO Red Book 5th Edition Ch 4).


VV ECMO is traditionally used in patients with any potentially reversible condition in which the lungs are unable to ventilate and oxygenate despite the use of optimal mechanical ventilation and treatment. VV ECMO may be used in neonates due to respiratory failure. The neonate must be in a facility that has expertise in neonate respiratory failure and has double lumen cannulas available for placement. It is also available to be used as a bridge to lung transplantation, enabling patients to be weaned from mechanical ventilation and mobilize, while waiting for the transplant procedure.


Venoarterial Extracorporeal Membrane Oxygenation Cannulation Sites

Neck Cannulation(颈部插管)

The venous cannula is inserted in the right internal jugular vein and the arterial cannula is inserted in the right common carotid artery. Using the internal jugular vein for drainage, an alternative cannulation strategy for a larger pediatric patient and/or adult patient can be used to deliver oxygenated blood using the right subclavian artery or axillary artery. Alternative cannulation technique (subclavian or axillary) can be used as it may permit increased mobility for the patient whereas reducing complications seen with groin cannulation all while preserving the carotid artery (Figure 1). (ELSO Red Book 5th Edition Ch 5).



Central Cannulation(中心插管)

Central cannulation includes direct venous cannulation into the right atrium and direct arterial cannulation of the ascending aorta. Central cannulation is most used for patients who cannot be weaned from cardiopulmonary bypass (CPB) in the operating room (OR). CPB is for short-term heart and lung support during cardiac surgical intervention. It uses a reservoir as well as an open circuit configuration for medication and volume access. ECMO is for long-term use and uses a closed configuration. Conversion between CPB and ECMO can be performed using the existing cannula. Central cannulation may be used to obtain higher bloods flows to fully support the patient’s metabolic needs during clinical conditions such as sepsis. Central cannulation enables more optimal drainage and thus better unloading of the heart than peripheral VA ECMO (Figures 2 and 3).


图2.静脉-动脉体外膜肺氧合(VA ECMO)插管策略
图3.带有远端灌注插管的静脉-动脉体外膜肺氧合(VA ECMO)动脉插管

Femoral Vein and Femoral Artery Cannulation(股静脉和股动脉插管)

Femoral vein and femoral artery cannulation are generally used for VA ECMO cannulation in adults and potentially children that are larger than 30kg. If the femoral artery is cannulated, a reperfusion cannula to that limb will ideally be placed to prevent limb ischemia, unless the cannulation was performed using a graft technique ensuring adequate blood flow to the lower limb. It can be beneficial during extracorporeal cardiopulmonary resuscitation (ECPR), either percutaneously or via cutdown, due to the ability to cannulate with less interference or cessation of chest compressions as in central cannulation. Due to the dual circulations (native output versus ECMO output), there will always be a degree of differential oxygenation between the upper and lower body, depending on the degree of native left ventricle and lung function. This will become more pronounced when the native lung function is poor, and the left ventricle contractility is improving. This mixing of deoxygenated blood via native cardiac output should be assessed as it can lead to myocardial and/or cerebral ischemia (ELSO Red Book 5th Edition Ch 4). It will be important to ensure the presence of a right upper extremity arterial line (right radial arterial line is preferred), cerebral oximetry, and/or pulse oximetry in the same position as the arterial line (Figure 4).



Venovenous Extracorporeal Membrane Oxygenation Cannulation Sites

Single Site Cannulation(单部位插管)

Dual lumen cannula with the tip in the right atrium; here blood is drained via the superior vena cava (SVC) and right atrium (RA) with the oxygenated blood returned into RA towards tricuspid valve into the pulmonary artery (PA). Bicaval cannula with the tip of the cannula in the inferior vena cava (IVC); here the blood is drained via IVC/SVC and the oxygenated blood is returned via RA towards tricuspid valve into the PA. A dual lumen cannula with a single drainage site might also be positioned into the main PA; here the venous blood is drained from the RA and the oxygenated blood is directly reinfused into the PA (Figures 5 and 6).


图5.静脉-静脉 (V-V)  单根置管 (右颈内静脉)
图5.静脉-静脉 (V-V)  单根置管 (右颈内静脉)

Two Site Cannulation(双部位插管)

Femoral vein/jugular vein: drainage from the femoral vein and return into the internal jugular vein or drainage from the jugular vein with blood return into the femoral vein. Femoral vein/femoral vein: drainage with a shorter cannula in the bifurcation of the femoral vein with a longer cannula returning in the right atrium or inferior vena cava. Femoral vein/pulmonary artery: drainage via a cannula posi- tioned in the RA via femoral vein and reinfusion of oxygenated blood via a second cannula positioned in the main PA through a direct or percutaneous (via the right internal jugular vein) cannulation (Figures 7 and 8).

股静脉/颈静脉:从股静脉引流,回流到颈内静脉;或从颈静脉引流,血液回流到股静脉。股静脉/股静脉在股静脉分叉处用较短的插管引流,在右心房或下腔静脉用较长插管回流股静脉/肺动脉:经股静脉置入右心房的插管用于引流,另一根直接置入肺动脉的插管或经皮(经右颈内静脉) 置入肺动脉主干内的插管回输氧合血液(图7和8)。

图7.静脉-静脉 (V-V) 股静脉-右颈内静脉置管
图8.两部位点静脉体外膜肺氧合 (VV- ECMO) 置管策略


Recirculation occurs in VV ECMO when the reinfused oxygenated blood is drained back into the ECMO circuit causing low systemic oxygenation and high ECMO circuit inlet saturations. (ELSO Red Book 5th Edition Ch 4). The amount of recirculation is directly related to the cannula position, pump flow, and cardiac output. Malposition of the cannula can greatly affect the amount of recirculation i.e. Right IJ catheter is too low with two site VV or rotated the wrong way with dual lumen catheters. It occurs when the pump blood flow rate is higher than the patient’s native cardiac output, due to left/right cardiac failure or severe pulmonary hypertension. With adequate cardiac output and proper cannula position, pump flow increases oxygenation delivered to the patient.



再循环可通过计算再循环分数来估计:SPREOx- SvO2/ SpostOx- SvO2。 有效流量计算:总流量-(总流量*再循环分数)。

Recirculation Symptoms: Patient arterial desaturation SVO2 and SpO2 will have a small differential between them. (Example: SVO2 87% and SPO2 92%) or in severe cases the SVO2 may be higher than the SPO2 (SVO2 92% and SPO2 87%). The venous blood will be similarly bright red as the post oxygenator blood. If pre and post oxygenator O2 saturations are measured, both O2 saturations will be very high and only small differences will be noted (Figure 9).

再循环症状:病人动脉血氧饱和度下降。SVO2和SpO2之间差值会很小。(例如:SVO2 87%,SPO2 92%)或在严重的情况下,SVO2可能高于SpO2(SVO2 92%,SpO2 87%)。静脉血将与膜肺后的血液同样呈鲜红色。如果测量膜肺前和膜肺后的血氧饱和度,两个氧饱和度都会很高,差异非常小(图9)。


Cannulation Selection(插管选择)

Selection of the right cannula is vital for a successful ECMO run and needs to be carefully selected for each individual patient. Blood flow needs to be sufficient in quantity, but also important is the efficiency in terms of where blood is drained and returned. The choice of the cannula is not only guided by the aimed degree of support, but also by the size and condition of the vessel, patient size, possible site of placement, type of insertion procedure, and desired location of blood drainage/ return. (ELSO Red Book 5th Edition Ch 4). Cannula size or diameter refers to the outer diameter of the cannula and is expressed in French (1FR = 0.33 mm). Diameter size should be selected in accordance with the desired amount of flow for the individual patient and can be guided using the pressure drop/flow charts of the available cannula (instructions for use).

合适的插管对于成功实施 ECMO 至关重要。因此,需要为每个患者仔细选择最合适的插管。在进行ECMO时,不仅需要足够的血流量,而且需要足够的血液引流和回流的效率。插管的选择不仅取决于目标支撑程度,还取决于血管的粗细和状况、患者体型大小、可能的放置部位、置管方式以及所需的血液引流/回流位置。(ELSO 红皮书第 5 版第 4 章)。插管型号或直径是指插管的外径用French表示 (1FR = 0.33 mm)。插管型号的选择需要依据每个患者所需的血液流量,这可以参考导管的压降/流量图(使用说明)。

Pressure Drop(压降)

Pressure drop is the difference in pressure entering the cannula and the pressure leaving the cannula. It is directly proportional to the cannula length and the viscosity of the fluid, and inversely proportional to the fourth power of cannula diameter. So, doubling the length will double the pressure drop, and doubling the size will reduce the pressure drop to 1/16th of baseline. Common practice is not to exceed a pressure drop of 100 mmHg. Hemolysis might be monitored routinely to determine nonturbulent blood flow through the cannula. Pressure drop versus flow charts are commonly used to determine the right size cannula. It should be noted that the manufacturer charts are tested using water which is an underestimation of the actual pressure drop in the blood. The Hagen–Poiseuille equation can be used to describes the relationship between pressure, resistance and flow rate (Figures 10 and 11).

压降是指血液进入导管的压力与离开导管的压力之差它与导管长度和流体粘度成正比,与导管直径的四次方成反比。因此,长度增加1倍将使压降增加1倍,导管直径增加1倍将使压降降低到1/16。压降通常要求不超过 100 mmHg。可以常规监测溶血以确定非湍流血流通过导管。压降-流量图可用于确定指导插管尺寸的选择。应该注意的是,厂商提供的压降/流量图的数据是使用水进行测试得来的,这低于血液中的实际压降。哈根-泊肃叶方程可用于描述压力、阻力和流量之间的关系(图10和11)。


Cannula design(导管设计

Tip design and side ports(尖端设计和侧孔

The number and position of side ports are important as it has an impact on pressure drop, the location of blood drainage, and blood reinfusion. The most common cannula designs: Blunt tip cannula: one central hole at the tip. Lighthouse tip cannula: central hole with some distal side holes around the tip. Multistage cannula: side holes at different stages along the cannula. Interrupted multistage cannula: multiple drainage ports along cannula. Number of lumen (1 or 2): dual lumen for ECMO with single insertion site (VV ECMO). Connection with tubing: with or without connector, connec- tion size (1/2”, 3/8”,1/4”, and 3/16”). Coating: to optimize biocompatibility.Wiring and stiffness: to avoid cannula kinking or collapsing. Cannula insertion tools: suited guidewires (length, stiffness, and curves) and vessel dilators (tip design, smooth transition with cannula tip) are important for uncomplicated percutaneous insertion.Cannula indicators: for placement control (Figure 12).

侧孔的数量和位置很重要,因为它对压降、血液引流位置和血液回流都有影响。最常见的导管设计钝头导管:尖端有一个中心孔。灯塔尖端导管:中心孔周围有一些远端侧孔。多级导管:沿导管的不同节段有侧孔。间断多级导管:沿导管有间断引流孔。腔数(1 或 2):单根双腔导管(VV- ECMO)。与管路连接:带或不带连接器,连接尺寸(1/2”、3/8”、1/4” 和 3/16”)。涂层:优化生物相容性。接线和刚度:避免插管扭结或塌陷。导管插入工具:合适的导丝(长度、硬度和曲率)和血管扩张器(尖端设计,与导管尖端的平滑过渡)对于非复杂性的经皮置管很重要。导管指示器:用于指示导管放置位置(图 12)。


Overview of an extracorporeal membrane oxygenation circuitECMO回路概述

ECMO circuits are similar for VV and VA ECMO, except that there might be extra cannulas/lines added in VA ECMO; an extra drainage line can be added if direct left ventricular unload- ing is performed via the ECMO circuit, or a return line can be added if distal perfusion of the cannulated limb is performed via ECMO. In cases of hybrid ECMO (veno-venoarterial or VP), additional drainage and return lines are hooked up to the extra cannula. These lines need to be safely incorporated in the circuit all while monitoring the additional flows. Understandably, there are different ECMO circuit sizes depending on the size of the supported patient, or the degree of required support. Size can be influenced by the choice of the oxygenator, pump, and diameter/length of the tubing (Figure 13). (ELSO Red Book 5th Edition Ch 5).

VV-ECMO 回路与VA-ECMO 类似,只是 VA-ECMO 中可以额外增加回路;如果通过ECMO 回路进行直接左心室卸载,则可以增加额外的引流管,如果通过ECMO 进行插管肢体的远端灌注,则可以增加回流管。在混合 ECMO(VV-A或VP)的情况下,额外的引流管和回流管可以连接到外部管路。这些管路需要安全地整合到回路中,同时监测额外的流量。可以理解,根据患者体型大小或所需的支持程度,有不同的 ECMO 回路大小选择。回路的尺寸选择受氧合器、泵和管道直径/长度的影响(图13)。(ELSO 红皮书第 5 版第 5 章)。


Circuit composition回路组成

The length of the tubing is center-specific. The longer the tubing, the more resistance, and the more artificial surface the patient will be exposed to. However, there needs to be enough tubing to be able to properly mobilize the patient, operate in other areas in the hospital such as the catheterization lab or the OR, and transport if needed (Figure 14).


Bridge (optional): A bridge connects the venous side of the circuit to the “arterial” side or post oxygenator using addi- tional connectors. Centers have used various types of bridges to accommodate other needs such as continuous arterial blood gas monitoring or maintaining safe flows with weaning. The bridge is used mainly for weaning neonatal and pediatric patients from VA ECMO to maintain the circuit integrity during the weaning period.

桥接器(可选):桥接器使用附加连接器将回路的静脉侧连接到“动脉”侧或氧合器后。可使用各种类型的桥接器来满足其他需求,例如连续动脉血气监测或在撤机时保持安全流量。桥接器主要用于新生儿和儿科患者VA-ECMO 撤机,可以使撤机期间保持回路完整性。

Bladder (optional): A bladder can be used to attenuate the negative venous line pressures generated by the centrifugal ECMO pump. The idea of the bladder is to act as a buffer by eliminating any trauma caused by excessive suction with the drainage catheter. The bladder is mandatory for roller pumps because it also acts as a servo-controller for the pump. The Better-Bladder allows the venous line pressure to be measured in its chamber without accessing the circuit, reducing the risk of air embolism. If no bladder is present, an additional connector with a luer-lock may be used to continuously monitor venous line (pump inlet) pressures.


Shunt (optional): If a shunt line is used, a luer connector can be added with additional tubing to direct blood flow from the positive pressure side (post oxygenator) of the circuit to the negative pressure side (pre oxygenator) of the circuit.

  1. Benefits of Shunt: Additional monitoring such as a continuous pump arterial blood gas may be obtained through the shunt. The additional flow provided through the shunt to the oxygenator may prevent the bridge being opened when weaning flows of smaller patients. A hemofilter may be placed in the shunt for slow continuous ultrafiltration (SCUFF).
  2. Disadvantages of Shunt: Additional connectors might induce clots and/or hemolysis, it requires additional flow monitors to assess the circuit shunt, it increases the complexity of the circuit and decreases the safety of the circuit as there is an additional risk of draining air into the negative pressure side.

 分流器(可选):如果使用分流器,则可以添加带有额外管道的鲁尔接头,以将血液从回路的正压侧(氧合器后)引导到回路的负压侧(氧合器前)。(1)分流器的优点:通过分流器可以进行额外的监测,例如通过分流器留取连续泵送动脉血气。通过分流器提供给氧合器的额外流量可能阻止桥接器在小儿患者撤机时打开。可以在分流管中放置一个血滤器以进行慢速连续超滤 (SCUFF)。(2) 分流器的缺点:分流器可能会导致血栓和/或溶血,它需要额外的流量监测器评估回路分流。由于存在空气进入负压侧的风险,因此它增加了回路的复杂性并降低了回路的安全性。

Access can be obtained in the tubing from the pump head to the oxygenator by inserting connectors with luers for obtaining labs, administering medication and/or blood products.

  1. Be aware: High pressures postpump will complicate administration of fluids and medications, and regular access may increase the risk of infection or breaking off luer locks.

Pressure transducers can be added immediately before the inlet of the oxygenator to monitor premembrane pressures and after the oxygenator to monitor postmembrane pressures. An additional transducer can be added before the pump to mea- sure drainage pressures. Pressure transducers, although not necessary, can provide information relevant to patient care while on ECMO.




Sizes: Generally, patients less than 10–15kg have 1/4” tubing. Patients greater than 15kg typically have 3/8” tubing. (ELSO Red Book 5th Edition Ch 5) Coating: The addition of a precoating or surface modifi- cation to the ECMO circuit may be employed to reduce the adsorption of plasma proteins to the ECMO circuit and thus thrombus formation. Plasma protein adsorption to the biomaterial surface leads to platelet adhesion/activation and thrombin activation, ultimately resulting in the formation of a thrombus. Varieties of coatings exist as the perfect biocompatible surface has not yet been discovered. The addition of 25% albumin can be administered to the crystalloid primed circuit as a coating and potentially add oncotic properties (ELSO Red Book 5th Edition Ch 5). There are heparin and nonheparin surface coatings available. In case of heparin-induced thrombocytopenia, it is advisable to use a nonheparin leaching circuit.


Extracorporeal Membrane Oxygenation Oxygenator(氧合器)

The ECMO oxygenator is designed to administer oxygen, remove CO , and in most designs warm the blood (Figure 15). The membrane most used is made of polymethylpentene (PMP). Modern oxygenators are characterized by a low resistance to blood flow, low priming volume, easy deairing, and rare incidents of plasma leakage (ELSO Red Book 5th Edition Ch 5). Typical ranges of prime volumes range from 80mls in the smaller neonatal pediatric specific oxygenators to 250ml in the larger adult oxygenators.



Blood Flow 血流量

The rated blood flow must be able to transfer the amount of oxygen being consumed by the patient. (Please see table below selection of an oxygenator).  设定的血流速度必须能够输送病人所消耗的氧气量。

Sweep Gas 气流量

A mixture of oxygen and air administered directly to the oxygenator gas port (a blender can be used based on etiology and patient size). Increasing the sweep gas flow rate increases CO2 clearance. Decreasing the sweep gas flow rate decreases CO2 clearance. 空氧混合气体直接接入氧合器的气体接口(空氧混合器可以根据病因和病人的体型来使用)。气体流速的增加将会增加清除CO2的能力,气体流速减小将降低清除CO2的能力。

Pressure gradient 压力梯度

The pressure gradient equals the difference between oxygenator inlet and outlet pressures. The pressure gradient reflects the internal resistance inside an oxygenator and its function of the specific oxygenator design in relation to the blood flow and internal buildup of deposits. Pressure drops across oxygenator membranes differ per the oxygenator manufacture. Calculating/documenting hourly pressure drops divided by flow is a common practice in some ECMO centers. If the pressure gradient rises gradually or suddenly independent of flow, resulting in an increasing quotient, this is a good indicator of oxygenator clot formation (Figures 16 and 17).



Complications Related to the Oxygenator(氧合器相关的并发症)

The ELSO registry defines a “failing oxygenator” as “requiring change due to clot formation, gas exchange failure, or blood leak”. Whenever an oxygenator no longer allows sufficient blood passage, gas transfer, or becomes a potential burden to the patient (in terms of inducing consumptive coagulopathy or not providing the required gas transfer), a replacement needs to be considered and an elective change-out needs to be planned as soon as possible. Postponing change-out can unnecessarily further burden the patient and might lead to an urgent change-out in suboptimal conditions, which always should be avoided. On the other hand, unnecessary change-outs also need to be avoided as these are invasive actions requiring a short support interruption, potentially causing iatrogenic infections, renewed blood dilution, additional platelet consumption as well as inflammation due to renewed surface contact activation. Additionally, ECMO oxygenator or circuits resources are burdened unnecessarily.


Increased Pressure Gradient Over an Oxygenator 氧合器压力梯度升高

Different oxygenators on the market show a different internal resistance depending on individual design and size properties, all allowing different flows at a certain driving pressure. A rise of the pressure drop is an indication of increased internal resistance, and if accompanied by a drop in flow for the same pump rotations, an indication of embolization inside the oxygenator. If not accompanied by flow reduction for the same pump rotations, there might be a pressure measurement error, which will then need to be resolved. Whenever the ECMO blood flow is relatively low in relation to the oxygenator capacity, pressure drop changes can be too subtle to serve as an early warning for clot formation. In the case of a clotted CRRT, oxygenator pressure measurements can be falsely elevated if these are measured at the site of the CRRT connection. A clotted CRRT might lead to oxygenator thrombi. Therefore, clotted CRRT devices should be removed immediately and in case of repeated clotted CRRT devices, an alternative access should be considered to connect the CRRT device.


Blood Tests 血液检查

A change of trend in coagulation test results while on ECMO might indicate that clot formation is ongoing, such as rapid rising D-dimers and dropping platelet numbers. There always must be an exclusion of other potential reasons for changes in these parameters. D-dimers are very sensitive to circuit clots but can also suddenly rise due to other causes such as severe inflammation and intravascular thrombus. Most patients on ECMO show some degree of thrombocytopenia from the start of ECMO, which does not necessarily indicate solid clot formation. However, platelets can form solid clots in cases of insufficient anticoagulation or heparin-induced thrombocytopenia (HITT); here an oxygenator change-out will be required. If HITT occurs, heparin needs to be substituted by alternative anticoagulation drugs.


Gas Transfer Performance 气体传输性能

Every oxygenator has its specific O2 transfer capacity, which can be found in the instructions for use by the manufacturer. This information gives an idea of the expected O2 transfer with a certain blood flow and gas flow of 100% FiO2. Oxygenation consumption requirements of patients can range in adults from 3 to 5ml/kg/min, pediatrics 4–6ml/kg/min, and neonatal 6–8 ml/kg/min.

每个氧合器都有特定的氧气输送能力,这可在制造商使用说明中找到。这些信息提供了预期氧气输送的概念即以一定的血流量和100% FiO2的气流量进行氧气输送的能力。患者的氧耗需求范围为:成人3-5ml/kg/min,儿童4-6ml /kg/min,新生儿6-8ml /kg/min。

Oxygen transfer during ECMO: Oxygen transferred during ECMO (V’O2) is calculated by the formula: V’O2 = BFR × (CpostO2 – CpreO2) (where V’O2 = O2 transfer across the membrane lung (ML) in ml/min, BFR = blood flow rate (L/min), C × O2 = O2 content of (pre-/post-ML) blood (ml/L). Calculating O2 content (CxO2):(CxO2): CxO2 = 13.4 × Hgb x SxO2 + 0.03 x PxO2 (Hb = hemoglobin g/dl, SxO2 = O2 saturation of pre-/post ml blood, PxO2 = PxO2 partial pressure of (pre/post-ML) blood (mm Hg) Example: (Hgb × 1.34) × (Post oxy sat – Pre oxy sat) + (PaO2 x.003) × flow (in deciliters) Patient with sp. Hct 35, SVO2 (circ) 71, SaO2 (circ) 100, Post oxygenator PO2 365 mm Hg, Pump flow 5 LPM To calculate oxygen transfer through the oxygenator: (12 × 1.34) × (1.0 – 0.71) + (365 × 0.003) × 50 = [(16.08 × 0.29) + 1.095] × 50 = (4.6632 + 1.095) × 50 = 5.7582 × 50 = 287.9 ml oxygen transfer per minute through the oxygenator CO2 transfer can be calculated as Inlet CO2 content – outlet content times blood flow, but it is more accurate to measure the amount of CO2 in the exhaust gas. CO2 transfer is always greater than O2 transfer if the membrane lung is functioning normally. CO2 transfer is controlled by adjusting the sweep gas.

ECMO时的氧输送:ECMO的氧输送 (VO2)可通过该计算公式计算:  VO2= BFR × (C膜后O2– C膜前O2)(其中VO2为每分钟通过膜肺的氧气量(ml/min),BFR为血流速度(L/min), C xO2为膜前/后血氧含量(ml/L)。CxO2计算公式:CxO2 = 13.4 *Hgb *SxO2+ 0.03 *PxO2。(Hb:血红蛋白含量(g/dl), SxO2:膜前/后血氧饱和度,PxO2:膜前/后血氧分压(mmHg))。举例(Hgb *1.34) *(膜后 – 膜前血氧饱和度) + (PaO2*0.003) *流量(分升)。患者的Hct为35%,SVO2(circ)为71,SaO2为 (circ) 100,氧合器后氧分压PO2 为365mm Hg,泵速为5LPM。那么计算通过氧合器的氧气输送量:=(12*1.34)*(1.0 – 0.71) + (365*0.003)*50= [(16.08*0.29) + 1.095]*50= (4.6632 + 1.095) *50= 5.7582*50= 287.9ml/min氧气通过氧合器。二氧化碳清除量可以通过计算氧合器输入端CO2含量减去输出端含量再乘以血流量,但测量废气中二氧化碳量更准确。如果肺膜功能正常,CO2排出量总是大于O2输送量。CO2的排出是通过调节气体流速来控制的。

Membrane lung malfunction 膜肺故障

A calculation of O2 uptake inside the oxygenator can provide useful information with regard to the oxygenator performance. Comparing the O2-transfer by what is indicated on the instructions for use by the manufacturer might give us insight on the mL performance, but a daily trend is more important than absolute values. Before oxygenator blood is drawn for blood gas analysis, oxygenator gasses should be set at 100% FiO2 to correctly compare mL transfer capacities with the IFU. A post-oxygenator pO2 might already be indicative of sufficient O2 transfer; taken at a gas flow of FiO2 of 100%, values should exceed 300 mm Hg of PaO2. A daily blood gas control might detect deterioration of the oxygenator, and if this hap- pens accompanied by insufficient patient support, change-out needs to be considered. Similar observations can be made to detect a decline in CO2 removal. Here, the cause can simply be a wet membrane: Increasing the sweep gas for a few seconds to remove condensation or clear an obstruction that is preventing gas exchange, can improve oxygenator function. This should be performed if there is a suspicion of oxygenator failure. If mL CO2 removal rate is less than 10mm Hg despite max gas flow an oxygenator change-out should be considered. Manufacturer DNE (do not exceed) sweep gas flow rates should be noted and observed as high gas flow rates can exceed the pressure limitation set by each oxygenator resulting in membrane rupture.


Visible clots 肉眼可见的血栓

Clots might be visible in the oxygenator depending on the design. Most clots will be situated at the venous side of the device, where internal resistance directs the blood passage through certain paths. The areas with the lowest velocity, highest resistance, or lowest wash-out will most likely clot off first. Clot growth needs to be observed and a component change should be considered if this accompanies a decreased blood flow with the same rpms, a burden to the coagulation profile of the patient (consumptive coagulopathy), hemolysis (increased PfHb), or insufficient patient support.


Oxygenator blood volume 氧合器的血容量

Measurement of the transit time of a saline bolus passing through the oxygenator as recorded by a sensor placed pre and post oxygenator can enable a quantitative assessment of oxygenator performance (Figure 18).



The ECMO Blood Pump ECMO血泵

The blood pump controls the required blood flow for the patient. There are different designs available; roller pumps and centrifugal pumps, of which centrifugal pumps are currently the most used. (ELSO Red Book 5th Edition Ch 5).


Roller pumps 滚轴泵

Generate direct suction on the pump inlet tubing which can be limited by a bladder (reservoir) box servo-controller to pre- vent excessive drainage catheter suction. The tubing can wear or rupture in the pump head or if there is an occlusion to the tubing after the pump (Figure 19).



Centrifugal pumps 离心泵

Magnetic driven pump rotor with axis control that gener- ates negative suction at a central hub by high rotational speed; blood is expelled via lateral hole. All centrifugal pumps have their specific control consoles which ensure pump operation, and each have certain monitoring and safety features (flow, air bubbles, pressures, visual, and auditory alarms). Most have backup batteries. There should always be a backup available (hand crank, backup motor, or spare console). If ECMO transport needs to be performed, a safely transportable system needs to be available.Performance is related to rpms and is dependent on preload and afterload (Figures 20–22).

离心泵通过磁力驱动泵转子并具有轴向控制,通过高转速在泵头中心位置产生负压; 血液则通过侧孔排出。所有的离心泵都有特定的控制台,以确保泵的运行,每个都有特定的监控和安全功能(流量、气泡、压力、视觉和听觉警报)。大多数离心泵都有备用电池。任何情况下都应该有备用的泵头(手动泵、备用电机或备用控制台)。如果需要进行ECMO转运,则需要一个安全的可转运的系统。离心泵的性能与转速相关,并依赖于前负荷和后负荷(如图20-22)。


Priming the Circuit 预充回路

Circuits are primed with crystalloid solutions and/or blood products based on center preference under sterile conditions. (ELSO Red Book 5th Edition Ch 5). 在无菌条件下,根据中心的偏好,用晶体液和(或)血液制品来预充回路。(ELSO红皮书第5版第5章)。

Blood Prime 血液预充

Infants and small pediatric patients approximately <10– 15kg should have the circuit primed with blood (packet red blood cells + hemodilution) before initiation of ECMO support, unless cardiopulmonary resuscitation is in progress, whereas the goal is to establish ECMO support as soon as possible. Blood prime additives may include NaHCO3, CaCl, Heparin, FFP, and 25% albumin. It is advisable to check the electrolyte composition of the blood prime before initiating ECMO.

在开始ECMO支持之前,婴儿和体重小于10–15 kg小儿科患者应使用血液(压积红细胞+血液稀释液)预充回路,除非正在进行心肺复苏,这时的目标是尽快建立ECMO支持。血液预充的主要添加剂可能包括NaHCO3、CaCl、肝素、FFP和25%白蛋白。建议在开始ECMO前检查预充液中的电解质成分。

Crystalloid prime 晶体液预充

Patients >10–15kg can be primed with a crystalloid solution, but this is also dependent on the circuit to patient volume or hemodilution. 大于10–15 kg的患者可以使用晶体液进行预充,但这也取决于回路对患者的容量或血液稀释的影响。

ECMO Circuit In-Line and Online Monitoring ECMO回路监测

ECMO circuit monitors either connected in or placed on the circuit are intended to measure the ongoing function of the circuit and alert the operator of any undesirable conditions. Each institution should examine if pressure monitoring is appropri- ate for their ECLS patient population (Figure 23). (ELSO Red Book 5th Edition Ch 5).



Flow monitors 流量监测

Blood flow is typically monitored directly with ultrasonic flow meters on the circuits with centrifugal pumps or calculated from tubing capacity and revolutions per minutes for roller pumps. Direct monitoring should be considered with roller pumps to ensure proper occlusion and accurate blood flow.


Circuit pressures monitoring 回路压力监测

Inlet pressure (P1): the amount of negative pressure produced from pulling blood from the patient toward the pump. For roller pumps, servo inlet pump regulators should be utllized to ensure that gravity siphon does not result in cavitation from excessive negative pressure or air entrainment from various connectors or stopcocks. For centrifugal pumps, monitoring inlet pressure can be achieved by a circuit pressure monitoring device, which in some pumps can serve as an automatic rpm’s regulator in case of exceeding negative pressure limits (Figure 24). Pre-oxygenator pressure (P2): the pressure between the pump and oxygenator. Post-oxygenator pressure (P3): the pressure in the circuit after the oxygenator. Transmembrane pressure gradient or pressure drop (∆P) is determined by the difference between the pre-oxygenator and post-oxygenator pressure and reflects the internal resistance within an oxygenator (Figures 25–27).

入口压力(P1):将血液从患者引流到泵产生的负压。对于滚轴泵,应使用伺服入口泵调节器,以确保重力虹吸不会因过度负压或各种接头或三通吸入空气而导致气穴。对于离心泵,可通过回路压力监测装置来监测入口压力,在某些泵中,当超过负压极限时,该装置可自动调节泵的转速(图24)。氧合器前压力(P2):泵和氧合器之间的压力。氧合器后压力(P3):氧合器后回路中的压力。跨膜压力梯度或压力降 (∆P) 由氧合器前和氧合器后的压力差确定,反映氧合器内的阻力(图25-27)。

图24. 离心泵回路压力
图25. 离心泵ECMO回路中的3个不同压力区,离心泵ECMO回路中的压力区是相对值,并且与某些变量有关
图26. 离心泵ECMO回路中的压力区是相对值,并且与某些变量有关
图27. 压力、流量和转速之间的关系——可能的原因和纠正措施

Peripheral arterial O2 saturation monitoring 外周动脉血氧饱和度监测

Arterial O2 saturation (SaO2) is the fraction of oxygen-saturated hemoglobin relative to total hemoglobin in the blood.  动脉血氧饱和度(SaO2)是血液中氧合血红蛋白相对于总血红蛋白的分数。

Bubble detection 气泡检测

Bubbles can be detected using a noninvasive ultrasonic sensor placed on the circuit or visual recognition. A bubble detector is preferably placed postoxygenator to ensure gross air is not administered to the patient. This can be turned off during circuit maintenance to avoid confusion of air detection. The bubble detector should be in use during routine care, especially if the postoxygenator side of the circuit will be accessed routinely.


Battery indication 电池指示

The console should always be plugged into an electrical out let which is designated for emergency backup electricity. 控制台应始终插入指定用于应急备用电源的电源插座。

Pre-primed ECMO Circuits on Standby 提前预充的备用ECMO回路

Due to the time it takes to assemble and prime the ECMO circuit, many centers keep circuits assembled and filled with a crystalloid solution and will administer additives when ECMO is needed (see Priming the Circuit above). Due to the time and meticulousness that is required to not contaminate the circuit, it is best to assemble, and crystalloid primes the circuit in a con- trolled situation versus an emergent circumstance. Using the sterile technique and a solution that does not have substrates for bacterial growth, the circuit is unlikely to grow bacteria over time if contamination is prevented during standby times. Per ELSO’s Infection Control Guidelines, “it is safe to maintain prep- rimed circuits for up to 30 days, and possibly beyond 30 days, if: 1) the circuit is constructed and primed using standard sterile techniques and 2) the prime is electrolyte solution-based, and no glucose-containing solutions or albumin are used within the prime.” (ELSO Red Book 5th Edition Ch 5).


Special ECMO Configuration 特殊ECMO配置

An additional cannula may be configured into the circuit because of lack of drainage (adding a [venous] drainage catheter) or the need of additional oxygen delivery (adding an additional return catheter). The use of flow-controlling maneuvers (Hoffman clamp) may be needed in these configurations to deliver desired blood flows to certain areas of the patient. Additional flowmeters can be used to determine accurate flows going to each location.


When and where to clamp off the ECMO circuit? 何时何地夹闭ECMO回路?

Weaning from ECMO 撤离ECMO

Decreasing the amount of support to the patient to determine the patient’s readiness to come off ECMO support (Figure 28). When weaning, one must be cognizant of the minimum flow required through the oxygenator as recommended by the manufacturer. To achieve the minimal flow indicated by the manufacturer, the bridge can be opened (if applicable) or a shunt can be added to the circuit, which will increase the blood flow through the oxygenator while maintaining low blood flows to the patient. (ELSO Red Book 5th Edition Ch 51).


图28. 在哪里夹闭体外膜肺氧合(ECMO)回路


Low flow trial 低流量试验

Consider additional anticoagulation or increase anticoagu- lation levels, to prevent clot formation during low flow trials with a VA ECMO wean. Wean gradually during a low flow trial according to institu- tional protocol. Do not leave blood flow under recommended low blood flow limits longer than necessary. Pump controlled retrograde flow can also be used.

在VA ECMO撤机行低流量试验时,考虑额外的抗凝或增加抗凝水平,以防止血栓形成。根据所在机构的流程,在低流量试验期间逐渐撤机。不要让血流量低于推荐的低血流量限值的时间长于必要。也可以使用泵控制的逆流试验。

Clamp trial 夹闭试验

Consider brief clamp trials in neonatal and pediatric patients before decannulation.考虑在新生儿和儿科患者拔管前进行短暂的夹闭试验。


Turning off the sweep gas to the oxygenator: the gas line can be disconnected to ensure there is no gas exchange occurring. A VV clamp trial does not require clamping off blood flow because there is no cardiac support being provided to the patient. Capping off is usually done for a minimum of several hours to assure patient’s tolerance of decannulation.


Terminology 术语

For nomenclature terminology for different types of ECMO, please refer to the extracorporeal life support organization maastricht treaty for nomenclature in extracorporeal life support, a position paper of the extracorporeal life support organization.关于不同类型ECMO的命名术语,请参考体外生命支持组织的立场文件《体外生命支持术语马斯特里赫特条约》。


The authors thank Christine Stead, CEO, Peter Rycus, Executive Director, and the Members of the Board for their invaluable contribution to the development of this guideline


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  3. Extracorporeal Life Support Organization Registry: The ELSO Registry. Retrieved from www.ELSO.org. ELSO Data Registry Guidelines – Definitions. Accessed February 2021.
  4. Zachary B, Vercaemst L, Mason P, et al: How I approach mem- brane lung dysfunction. Critical Care 24:671, 2020.
  5. Westrope C, Harvey C, Robinson S, Speggiorin S, Faulkner G, Peek GJ: Pump controlled retrograde trial off from VA-ECMO. ASAIO J 59: 517–519, 2013.
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