Extracorporeal CO2 Removal for Acute Decompensation of COPD

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide, resulting in a social and economic burden that is substantial and increasing. Exacerbations affect the prognosis and quality of life of patients with COPD. Hospital mortality of patients admitted for a hypercapnic exacerbation of COPD is approximately 10% and the long-term outcome is poor. In addition, hypercapnic exacerbation of COPD have serious negative impacts on patient quality of life, lung function and costs. Thus, prompt treatment of exacerbations may impact the clinical progression of COPD by ameliorating quality of life and prognosis.

The pathophysiological hallmarks of COPD patients include expiratory flow limitation and small airway closure. Under these circumstances, a prolonged expiratory time is the compensatory mechanism patients adopt to maintain a stable tidal breathing. COPD exacerbations result in higher respiratory rates and reduced expiratory time, leading to dynamic hyperinflation, elevated intrathoracic pressures, and excessive work of breathing. Alteration of the balance between (a) the decreased capacity of the respiratory muscles to generate pressure, and (b) the increased mechanical respiratory load due to expiratory flow limitation and small airway closure leads to CO2 retention. The consequent reduction of alveolar ventilation leads to a further worsening of CO2 retention and increased work of breathing. This vicious circle is the underlying mechanisms responsible of acute respiratory failure requiring admission in the intensive care unit (ICU) for ventilatory support.

Standard of care for patients with COPD exacerbation that need ICU admission for management of acute hypercapnic respiratory failure and severe respiratory acidosis is non-invasive ventilation (NIV). When NIV fails (arterial pH remains < 7.30), invasive ventilation through endotracheal intubation is initiated to restore adequate gas-exchange.

Extracorporeal circuits designed to remove CO2 (ECCO2R) have been used in patients with acute hypercapnic respiratory failure since ECCO2R may enhance the efficacy of NIV to remove CO2 and avoid the worsening of respiratory acidosis. Although available studies are limited to case series, several ECCO2R devices have been developed and proposed for the clinical use in patients with COPD. These systems often represent modifications of renal replacement therapy circuits, and are characterized by:

1. veno-venous by-pass systems
2. extracorporeal blood flow of 0.3-0.5 litres/min
3. 13 Fr bore catheters or a single co-axial catheter
4. very low doses or no heparin
5. minimal volumes for "priming"

This technological implementation of ECCO2-R is therefore closer to device for renal replacement therapy than full ECMO. CO2 is removed through a double-lumen catheter and constantly propelled, by a non-occlusive rotating pump, though an artificial membrane lung (a filter adding oxygen and removing carbon dioxide) connected to a source of 100% O2 (flow 6-8 liters/min). These systems are able to reduce PaCO2 by 20-25%.

A recent matched cohort study with historical control, compared "NIV-plus-ECCO2R" and "NIV-only" in patients at risk of NIV failure, and showed that (a) the hazard of being intubated was three times higher in patients treated with "NIV-only" than in patients treated with "NIV-plus-ECCO2R"; (b) hospital mortality was significantly lower in "NIV plus ECCO2R" than in "NIV-only" [8% (95% CI 1.0-26.0%) vs. 33% (95% CI 18.0-57.5%), respectively]. However, ECCO2R-related complications were observed in almost half of the patients. A recent systematic review evaluated the efficacy and safety of ECCO2R in patients with hypercapnic respiratory failure across 12 studies and showed that the majority of patients were either successfully weaned from mechanical ventilation or sustained on NIV, avoiding intubation. However, this high success rates, was associated with a high frequency of potentially severe complications.

The consistency of the above discussed data, and the observation of the continuous increase use of ECCO2R despite the lack of solid evidence confirm that the equipoise regarding the use of ECCO2R may justify a randomized clinical trial to evaluate whether patients with respiratory acidosis refractory to NIV should be intubated and take the risks associated with invasive mechanical ventilation, or should be connected to ECCO2R to avoid intubation, but run the risk of the potentially serious ECCO2R-related complication

Objectives:

The main objective of this randomized multicenter clinical trial is to test the hypothesis that in patients with acute life-threatening exacerbation of COPD, use of ECCO2R could increase event-free survival as compared to standard of care. Event free survival is defined as survival at day 28 free of any of the followings: (a) development of sepsis; (b) occurrence of a second episode of COPD exacerbation requiring or not mechanical ventilation; (c) occurrence of severe hypoxemia; (d) prolonged mechanical ventilation (e) death.