Opioid agents are commonly administered to control cough during fiberoptic bronchoscopy (FOB). Nevertheless, data defining the optimal remifentanil dosing when FOB is performed under ciprofol sedation remains insufficient. The present study was designed to determine the effective concentrations (EC) of remifentanil needed to attenuate bronchoscopy-related responses in elderly patients undergoing FOB with ciprofol sedation. Patients between 60 and 90 years of age with an American Society of Anesthesiologists (ASA) classification of I–III who were scheduled for fiberoptic bronchoscopy were recruited for this study. Participants were categorized into two groups based on sex (male and female). Remifentanil was given intravenously before the administration of ciprofol. The primary observations included reactions during the procedure, specifically vocal cord activity, coughing episodes, and patient movement. The median effective concentration (EC50) and the 95% effective concentration (EC95) of remifentanil needed to suppress these responses were estimated for each sex using Dixon’s up-and-down sequential design. In addition, a dose–response curve was established through Probit analysis. A total of 39 participants were included in the study, comprising 19 men and 20 women. The median effective plasma concentration (EC50) of remifentanil needed to attenuate responses during FOB with ciprofol sedation was 3.25 (2.75–3.26) ng/mL in males and 2.25 (1.75–2.25) ng/mL in females, showing a statistically significant difference (P = 0.0023). According to Probit modeling, the estimated EC50 values were 3.102 ng/mL (95% CI: 2.694–3.749) for males and 2.052 ng/mL (95% CI: 1.345–2.750) for females. The corresponding EC95 values required to suppress bronchoscopic responses were 3.741 ng/mL (95% CI: 3.366–7.699) in males and 2.943 ng/mL (95% CI: 2.456–9.533) in females. The data suggest a clear difference between male and female patients in the remifentanil concentrations (EC50 and EC95) needed to control bronchoscopic responses during FOB with ciprofol sedation, while still allowing preservation of spontaneous breathing in the elderly population.
