Impact of Extraperitoneal Dioxyde Carbon Insufflation on Respiratory Function in Anesthetized Adults: A Preliminary Study Using Electrical Impedance Tomography and Wash-out/Wash-in Technic

BACKGROUND: Extraperitoneal laparoscopy has become a common technique for many surgical procedures, especially for inguinal hernia surgery. Investigations of physiological changes occurring during extraperitoneal carbon dioxide (CO(2)) insufflation mostly focused on blood gas changes. To date, the impact of extraperitoneal CO(2) insufflation on respiratory mechanics remains unknown, whereas changes in respiratory mechanics have been extensively studied in intraperitoneal insufflation. OBJECTIVES: The aim of this study was to investigate the effects of extraperitoneal CO(2) insufflation on respiratory mechanics. PATIENTS AND METHODS: A prospective and observational study was performed on nine patients undergoing laparoscopic inguinal hernia repair. Anesthetic management and intraoperative care were standardized. All patients were mechanically ventilated with a tidal volume of 8 mL/kg using an Engström Carestation ventilator (GE Healthcare). Ventilation distribution was assessed by electrical impedance tomography (EIT). End-expiratory lung volume (EELV) was measured by a nitrogen wash-out/wash-in method. Ventilation distribution, EELV, ventilator pressures and hemodynamic parameters were assessed before extraperitoneal insufflation, and during insufflation with a PEEP of 0 cmH(2)O, 5 cmH(2)0 and of 10 cmH(2)0. RESULTS: EELV and thoracopulmonary compliance were significantly decreased after extraperitoneal insufflation. Ventilation distribution was significantly higher in ventral lung regions during general anesthesia and was not modified after insufflation. A 10 cmH(2)0 PEEP application resulted in a significant increase in EELV, and a shift of ventilation toward the dorsal lung regions. CONCLUSIONS: Extraperitoneal insufflation decreased EELV and thoracopulmonary compliance. Application of a 10 cmH(2)0 PEEP increased EELV and homogenized ventilation distribution. This preliminary clinical study showed that extraperitoneal insufflation worsened respiratory mechanics, which may justify further investigations to evaluate the clinical impact.