Hypercapnia and acute respiratory failure in intensive care medicine

Abstract

Hypercapnia is common in the intensive care unit (ICU) and may be the cause of or a complication of ICU admission. Hypercapnia and hypercapnic acidosis could affect the cardiovascular, respiratory, central nervous and immune systems as well as inflammation. Acute respiratory distress syndrome (ARDS) and hypercapnic acute respiratory failure (HARF) are the main causes of hypercapnia in the ICU. Hypercapnia in ARDS is most often a consequence of the so-called « protective ventilation ».  Its management requires first the optimization of invasive mechanical ventilation settings and the use of prone position. In cases of failure, the use of extracorporeal circulatory assistance techniques (veno-venous  extracorporeal membrane oxygenation : VV-ECMO, extracorporeal carbon dioxide removal : ECCO₂R) can be considered under certain conditions and needs further studies to better analyze the benefit-risk ratio.  For HARF, non-invasive ventilation (NIV) remains the reference treatment. There is a strong a physiological rationale, however, to consider the use of  high-flow nasal oxygen therapy (HFNO) in this situation, alone or in association with NIV, based on the first clinical data but results from prospective randomized studies are still pending.. The ECCO₂R could also be an interesting alternative technique in the management of HARF either to prevent intubation in cases of risk of NIV failure or to promote early weaning/extubation from mechanical ventilation in these patients. However, the real benefit and safety of ECCO₂R in these situations has yet to be demonstrated.