Fig. 1

Study protocol. Each patient hospitalized in cardiac surgery with elective cardiac surgery and ICU hospitalization was consecutively included when the diaphragm thickening fraction (TF) could be measured during spontaneous breathing trial (SBT). Preoperative (Day − 1) and postoperative (Day + 1) were measured when feasible to assess perioperative evolution. Diaphragm function was evaluated by the TF measured on the right hemidiaphragm as reference in the same semi-recumbent position. SBT: Spontaneous Breathing Trial; ICU: Intensive Care Unit; TF: diaphragm thickening fraction