A randomized, controlled trial of transcutaneous carbon dioxide monitoringduring ERCP

Background: Pulse oximetry, used to monitor oxygen saturation during endosc opy, does not directly measure hypoventilation. Study goals were to determi ne whether transcutaneous carbon dioxide (PtcCO(2)) monitoring during endos copic retrograde cholangiopancreatography (ERCP) prevents severe hypoventil ation and to assess the accuracy of clinical observation and pulse oximetry in detecting hypoventilation. Methods: All patients received intensive clinical and electronic monitoring including pulse oximetry. Supplemental oxygen was administered for pulse o ximetry < 90%. Patients were randomized to a treatment arm (group 1) where PtcCO(2) monitoring guided sedation or a control arm (group 2) where PtcCO( 2) was recorded but unavailable for guiding sedation. Results: Group 1 had significantly fewer episodes of severe carbon dioxide retention (rise in PtcCO(2) greater than or equal to 40 mm Hg above baselin e) than group 2 (0 of 199 versus 5 of 196, respectively p = 0.03), as well a shorter mean duration of procedure discomfort (8.3% of procedure duration rated as "uncomfortable" versus 11.5%, p = 0.04). Correlations between cli nical observation and objective measures of ventilation were poor: level of sedation versus PtcCO(2) (R = 0.3) or pulse oximetry (R = 0.06); slowest r espiratory rate versus PtcCO(2) (R = 0.4) or pulse oximetry (R = -0.4). Ptc CO(2) rises of greater than 20 mm Hg occurred without oxygen desaturation i n 10.7% of patients receiving supplemental oxygen. Conclusions: Carbon dioxide retention during ERCP is not reliably detected by clinical observation or by pulse oximetry in patients receiving suppleme ntal oxygen. The addition of PtcCO(2) monitoring prevents severe carbon dio xide retention more effectively than intensive clinical monitoring and puls e oximetry alone. The clinical relevancy of this observation needs to be de termined in an appropriately designed outcome study.