In physiological conditions, spontaneous ventilation is controlled by blood carbon dioxide (and pH) levels. In healthy animals, extracorporeal carbon dioxide removal leads to hypoventilation or apnea (Kolobow et al., 1977). During acute respiratory insufficiency, extracorporeal carbon dioxide removal may be used to control spontaneous ventilation, limiting risks of lung damage and relieving dyspnea (Crotti et al., 2012). However, little is known about how spontaneous ventilation changes in response to changes in extracorporeal carbon dioxide removal during acute respiratory insufficiency, especially in humans.

Aim of this study is to monitor changes in spontaneous ventilation in awake patients treated with extracorporeal gas exchange support because of acute respiratory insufficiency, in response to changes in extracorporeal carbon dioxide removal.

Inclusion Criteria:

• Acute Respiratory Insufficiency
• Extracorporeal gas exchange support
• The patient is spontaneously breathing (including assisted ventilation)

Exclusion Criteria:

- age below 18 yrs