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Extracorporeal carbon dioxide removal (ECCO2R) refers to a technique of life support focused on the removal of CO2 from blood rather than improving blood oxygenation.1 This chapter introduces the concept of ECCO2R and discusses some of the experience and future on this exciting topic. ECCO2R has been developed mainly with a view to applying it in patients with the most severe form of acute respiratory distress (ARDS).2 We will try, however, to widen the perspective to cover also the possible role of ECCO2R in the prevention of hyaline membrane disease3 and in the treatment of severe asthma,4–8 multiple bronchopleural fistulas,9–10 and severe chronic obstructive pulmonary disease.11
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The mainstay of supportive treatment in ARDS is mechanical ventilation, a lifesaving procedure introduced in the management of patients with bulbar polio in the great epidemic that struck Copenhagen in 1952. These patients, paralyzed by polio, required long-term artificial ventilation;12 they became the first critical care patients. The use of mechanical ventilators later was extended to all patients with severe acute respiratory failure, whose main problem often was altered gas exchange and not respiratory muscle weakness or paralysis. The critical care profession witnessed both the pros and cons of optimizing gas exchange through use of the ventilator: The focus shifted from high to low tidal volumes, from high to low airway pressures, and from high to lower inspired oxygen fractions (FIO2). It is provocative to consider how we support the failing lung. In ARDS, we use an artificial organ (the ventilator), which is designed to substitute for the respiratory muscles rather than to act as a gas exchanger. Technology has been the limiting factor for a widespread application of artificial gas exchange,13 but research and development continues at a promising pace.
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Membrane Oxygenators, Membrane Gas Exchange, and Membrane Lungs
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Extracorporeal oxygenation was first provided as a heart–lung machine to render major cardiovascular surgery feasible and safe.14 The first oxygenators were based on bubbling of oxygen through the blood or filming of blood in an oxygen atmosphere. To avoid the problems caused by the direct contact between blood and gas,15,16 Kolff designed a membrane oxygenator,17 which Clowes18 and Kolobow19 developed further into clinically applicable membrane gas exchangers.20–22 Attention was focused on extracorporeal oxygenation, and the term extracorporeal membrane oxygenation (ECMO) was coined. Very little attention was paid to concurrent CO2 removal: Hypocapnia was recognized as a common annoyance to be prevented by adding CO2 to the gas ventilating the oxygenator.
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In 1967, Ashbaugh et al23 described ARDS. Soon this became a very common diagnosis in critical care, and mechanical ventilation moved to center stage as the main supportive therapy.24 To optimize oxygenation, tidal ...