Extracorporeal carbon dioxide removal for acute respiratory failure

Acute respiratory failure is a life‑threatening condition. It can be categorised as acute hypoxic respiratory failure (abnormally low levels of oxygen in the blood) or acute hypercapnic respiratory failure (abnormally low levels of oxygen and abnormally high levels of carbon dioxide in the blood). Acute respiratory distress syndrome is a severe type of acute respiratory failure. It can be caused by conditions such as:

• sepsis

• pneumonia

• respiratory viruses

• chest trauma

• inhalational injury

• aspiration and

• pancreatitis.
  
  The most common cause of hypercapnic respiratory failure is an acute exacerbation of chronic obstructive pulmonary disease.

The management of acute respiratory failure involves treating the underlying cause and providing increased oxygen by non‑invasive or invasive ventilation.

The 2 main types of extracorporeal carbon dioxide removal (ECCO₂R) are venovenous (vvECCO₂R) and arteriovenous (avECCO₂R). In both types, cannulae are connected to a low‑resistance synthetic membrane device where exchange of carbon dioxide takes place. In vvECCO₂R, either a single-access double-lumen catheter or a dual-access system using 2 venous catheters is inserted into a large vein or veins (usually the femoral or internal jugular veins). It is then connected to a venovenous circuit. Flow across the membrane is maintained using a pump. In avECCO₂R, cannulae are inserted into an artery and a vein (usually the femoral artery and femoral vein). Arterial blood pressure drives blood continuously through the device and it is returned through the vein.

ECCO₂R can be done using either a true ECCO₂R system or a modified extracorporeal membrane oxygenation system. People having ECCO₂R are given blood‑thinning drugs such as heparin to prevent blood clots forming in the circuit.

For people with acute hypoxic respiratory failure, ECCO₂R aims to lower carbon dioxide levels in the blood, independently of the lungs. Lung‑protective ventilation settings such as lower airway pressures and lower tidal volumes can be used to reduce the risk of ventilator‑induced lung injury. But, using lung‑protective settings can cause carbon dioxide levels to rise, leading to negative effects. ECCO₂R is used to reduce blood carbon dioxide levels so that lung‑protective ventilation settings can be maintained. This may improve the likelihood and speed of lung recovery.

For people with acute hypercapnic respiratory failure, ECCO₂R aims to reduce the need for intubation and mechanical ventilation. It may also reduce the length of time that a person has non‑invasive ventilation.