Abstract:Objective To investigate the effective dose of ciprofol for suppressing insertion response during bronchoscopy when combined with remifentanil by using the sequential method ，and to provide a reference for rational clinical drug use. Methods Patients who underwent elective bronchoscopy under general anesthesia at the Eighth Affiliated Hospital of Southern Medical University from September 2023 to April 2024 were selected as research subjects. All patients were first administered an intravenous injection of remifentanil at a dose of 1 μg/kg. The modified Dixon’s up-and-down sequential method was used to determine the effective dose of ciprofol：the initial dose was set at 0.4 mg/kg，with a dose gradient of 0.05 mg/kg. If coughing，body movements，or other reactions that interfered with the examination occurred when the bronchoscope entered the trachea，this was termed“ineffective”，and the ciprofol dose for the next patient was increased by one dose gradient of 0.05 mg/kg. Conversely，if the reaction was“effective”，the ciprofol dose for the next patient was decreased by one dose gradient of 0.05 mg/kg. This process was repeated until seven turning points were observed.The Probit method was used to calculate the median effective dose（ED50），95% effective dose（ED95），and 95% confidence interval（CI）of ciprofol for inhibiting bronchoscope insertion response.Mean arterial pressure（MAP），heart rate（HR），and pulse oxygen saturation（SpO2）were recorded at 5 minutes before the start of anesthesia induction（T0），5 minutes after anesthesia induction（T1），at the time of bronchoscope insertion （T2），and at the end of the operation（T3）. The occurrence of adverse events such as intraoperative hypotension，hypoxemia，coughing，and postoperative nausea and vomiting（PONV）was also recorded. Results A total of 26 patients were enrolled in the trial，with 13 patients in the effective group and 13 in the ineffective group. The ED50（95%CI）of ciprofol for suppressing insertion response was 0.471（0.433-0.509）mg/kg and the ED95（95%CI）was 0.546（0.509-0.770）mg/kg. During sedation with ciprofol combined with remifentanil：compared with T0，HR significantly decreased at T1 and T3（P<0.05），and increased at T2 compared with T1（P<0.05）；MAP significantly decreased at T1 and T2 compared with T0（P<0.05），and partially recovered at T3 but remained lower than that at T0（P<0.05）；there was no statistically significant difference in SpO2 among all time points（P>0.05）. Additionally，there was no statistically significant difference in the incidence of adverse events between the effective group and the ineffective group（P>0.05）.Conclusion Ciprofol combined with remifentanil effectively suppresses insertion response during bronchoscopy，with ED50 and ED95 of 0.471 mg/kg and 0.546 mg/kg，respectively.