Table 3 Evaluation of CO₂ clearance of native lung during weaning from V–V ECMO

Ventilatory ratio [28]

(VE∙PaCO₂)/(PBW∙100∙37.5)

Assumes constant V’CO_2NL

Enghoff index

(PaCO₂ -PECO₂)/PaCO₂

Evaluates both shunt and dead space

Ratio of end tidal to partial pressure of carbon dioxide

EtCO₂/PaCO₂

Evaluates both shunt and dead space [20]

Bohr alveolar dead space

(PACO₂ -PECO₂)/PACO₂

Evaluates pure alveolar dead space but requires analysis of volumetric capnography curve [24]

Ventilatory efficiency

VE/ V’CO_2NL

No available data during ECMO

Ventilatory efficiency

∆P_eso/ V’CO_2NL

Influenced by lung elastance