Original article Comparison of Carbon Dioxide Absorption Rates in Gynecologic Laparoscopy with a Valveless versus Standard Insufflation System: Randomized Controlled Trial Obianuju S. Madueke-Laveaux, MD, MPH, Arnold Advincula, MD, Cara L. Grimes, MD, MAS, Ryan Walters, BS, Jin Hee Kim, MD, MS, Khara Simpson, MD, Mireille Truong, MD, Constance Young, MD, Ruth Landau, MD, and Timothy Ryntz, MD From the Departments of Obstetrics and Gynecology (Drs. Advincula, Walters, Kim, and Ryntz), Anesthesiology (Dr. Landau), Columbia University Medical Center, New York, New York, Department of Obstetrics and Gynecology (Dr. Madueke-Laveaux), University of Chicago, Chicago, Illinois, Department of Obstetrics and Gynecology (Dr. Grimes), New York Medical College, Valhalla, New York, Department of Obstetrics and Gynecology (Dr. Simpson), Johns Hopkins University, Baltimore, Maryland, Department of Obstetrics and Gynecology (Dr. Truong), Virginia Commonwealth University, Richmond, Virginia, and Department of Obstetrics and Gynecology (Dr. Young), Mount Sinai Hospital, New York, New York ABSTRACT Study Objective: The primary objective was to compare carbon dioxide (CO 2 ) absorption rates in patients undergoing gynecologic laparoscopy with a standard versus valveless insufflation system (AirSeal; ConMed, Utica, NY) at intra- abdominal pressures (IAPs) of 10 and 15 mm Hg. Secondary objectives were assessment of surgeons’ visualization of the operative field, anesthesiologists’ ability to maintain adequate end-tidal CO 2 (etCO 2 ), and patients’ report of postoperative shoulder pain. Design: A randomized controlled trial using an equal allocation ratio into 4 arms: standard insufflation/IAP 10 mm Hg, standard insufflation/IAP 15 mm Hg, valveless insufflation/IAP 10 mm Hg, and valveless insufflation/IAP 15 mm Hg. Setting: Single tertiary care academic institution. Patients: Women ≥ 18 years old undergoing nonemergent conventional or robotic gynecologic laparoscopic surgery. Interventions: A standard or valveless insufflation system at IAPs of 10 or 15 mm Hg. Measurements and Main Results: One hundred thirty-two patients were enrolled and randomized with 33 patients per group. There were 84 robotic cases and 47 conventional laparoscopic cases. CO 2 absorption rates (mL/kg*min) did not dif- fer across groups with mean rates of 4.00 § 1.3 in the valveless insufflation groups and 4.00 § 1.1 in the standard insuffla- tion groups. The surgeons’ rating of overall visualization of the operative field on a 10-point Likert scale favored the valveless insufflation system (median visualization, 9.0 § 2.0 cm and 9.5 § 1.8 cm at 10 and 15 mm Hg, respectively) over standard insufflation (7.0 § 3.0 cm and 7.0 § 2.0 cm at 10 and 15 mm Hg, respectively; p <.001). The anesthesiologists’ ability to maintain adequate etCO 2 was similar across groups (p = .417). Postoperative shoulder pain scores were low overall with no significant difference across groups (p >.05). Conclusion: CO 2 absorption rates, anesthesiologists’ ability to maintain adequate etCO 2 , and postoperative shoulder pain did not differ based on insufflation system type or IAP. Surgeons’ rating of visualization of the operative field was signifi- cantly improved when using the valveless over the standard insufflation system. Journal of Minimally Invasive Gynecology (2019) 00, 1-10. © 2019 AAGL. All rights reserved. Keywords: Carbon dioxide (CO 2 ) absorption; Insufflation; Laparoscopy; Shoulder pain The standard insufflation system works by introducing gas into the abdomen at a high flow rate (40 L/min) to reach a set intra-abdominal pressure (IAP). This high flow rate is sustained to maintain the IAP. In contrast, the valveless system introduces gas into the abdomen at a high flow rate (40 L/min) to reach a set IAP, but the gas flow is then Dr. Advincula reports personal fees from Abbvie, Applied Medical, and Intuitive Surgical; nonfinancial support from ConMed; royalties from Coo- per Surgical; and stock options from Titan Medical. Also, financial support was received by ConMed for this study in the form of an unrestricted grant. Corresponding author: Obianuju Sandra Madueke-Laveaux, MD, MPH, Department of Obstetrics and Gynecology, University of Chicago, 5841 S. Maryland Avenue, MC 2050, Chicago, IL 60637-1470. E-mail: somadueke@gmail.com Submitted March 18, 2019, Revised May 2, 2019, Accepted for publication May 3, 2019. Available at www.sciencedirect.com and www.jmig.org 1553-4650/$ — see front matter © 2019 AAGL. All rights reserved. https://doi.org/10.1016/j.jmig.2019.05.005