- shock state, - no spo2 signal available, - patient agitation, - ph < 7.30 (if blood gas available) - paco2 > 50 mmhg, (if blood gas available) or chronic hypercapnia history - non invasive respiratory support (niv, high flow nasal therapy (hfnt)) at study inclusion - withdrawal of life support or palliation as the goal of care - patients' or next of kin refusal to participate to the study

- shock state, - no spo2 signal available, - patient agitation, - ph < 7.30 (if blood gas available) - paco2 > 50 mmhg, (if blood gas available) or chronic hypercapnia history - non invasive respiratory support (niv, high flow nasal therapy (hfnt)) at study inclusion - withdrawal of life support or palliation as the goal of care - patients' or next of kin refusal to participate to the study