Fig. 1

Flow diagram of study subjects. All patients (n = 2760) underwent inpatient anesthesia and surgery. All patients were older than 18 years and underwent general anesthesia induction using propofol and tracheal intubation for non-cardiac surgery. Patients who had missing important covariates regarding intubation or hemodynamic data (n = 56), who did not receive oral intubation, or who underwent repeated attempts at intubation were excluded (n = 607). A total of 2097 participants were included in the analysis