title: Water exchange versus carbon dioxide insufflation in unsedated colonoscopy: a multicenter randomized controlled trial.
abstract: OBJECTIVE
  Compared with air insufflation, water exchange and carbon dioxide (CO2) insufflation have been shown to reduce colonoscopy discomfort; however, head-to-head studies of the two methods are lacking. We aimed to compare water exchange and CO2 insufflation directly with regard to pain during primary unsedated colonoscopy.
  
  
  METHODS
  Patients willing to undergo unsedated colonoscopy at three centers in Norway and Poland were randomized 1:1 to water exchange or CO2 insufflation during colonoscope insertion. Patients were blinded to group allocation. The primary end point was the proportion of patients reporting moderate or severe procedural pain on a 4-point verbal rating scale (VRS-4) at discharge. Secondary outcomes included the proportion of patients reporting no pain on the VRS-4.
  
  
  RESULTS
  A total of 473 patients were randomized. A discharge pain questionnaire was completed by 226 of 234 patients (97 %) in the water exchange group versus 226 of 239 patients (95 %) in the CO2 group (P = 0.37). Moderate or severe pain was reported by 47 of 226 patients (21 %) in the water exchange group versus 60 of 226 patients (27 %) in the CO2 group (P = 0.15). No pain was reported by 100 of 226 patients (44 %) and 69 of 226 patients (31 %) in the water exchange and CO2 groups, respectively (P = 0.003). On-demand sedation was used in 15 patients (6 %) in each group (P = 0.95).
  
  
  CONCLUSIONS
  There was no significant reduction in moderate or severe pain in a comparison of water exchange with CO2 insufflation. The secondary outcome of no pain was significantly more frequent in the water exchange group. Clinical trials registry number: NCT01633333.
authors.affiliation: Department of Medicine, Sorlandet Hospital HF, Kristiansand, Norway.
authors.forename: Kjetil
authors.initials: K
authors.lastname: Garborg
authors.affiliation: Department of Gastroenterological Oncology, Medical Center for Postgraduate Education and Institute of Oncology, Warsaw, Poland.
authors.forename: Michal F
authors.initials: MF
authors.lastname: Kaminski
authors.affiliation: Department of Medicine, Sorlandet Hospital HF, Arendal, Norway.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lindenburger
authors.affiliation: Department of Medicine, Sorlandet Hospital HF, Kristiansand, Norway.
authors.forename: Håvard
authors.initials: H
authors.lastname: Wiig
authors.affiliation: Department of Medicine, Sorlandet Hospital HF, Kristiansand, Norway.
authors.forename: Audun
authors.initials: A
authors.lastname: Hasund
authors.affiliation: Department of Gastroenterological Oncology, Medical Center for Postgraduate Education and Institute of Oncology, Warsaw, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Wronska
authors.affiliation: Department of Pathology, Sorlandet Hospital HF, Kristiansand, Norway.
authors.forename: Rolf Bruun
authors.initials: RB
authors.lastname: Bie
authors.affiliation: Department of Pathology, Sorlandet Hospital HF, Kristiansand, Norway.
authors.forename: Britta
authors.initials: B
authors.lastname: Kleist
authors.affiliation: Department of Pathology, Sorlandet Hospital HF, Kristiansand, Norway.
authors.forename: Leif
authors.initials: L
authors.lastname: Løvdal
authors.affiliation: Department of Medicine, Sorlandet Hospital HF, Kristiansand, Norway.
authors.forename: Øyvind
authors.initials: Ø
authors.lastname: Holme
authors.affiliation: Institute of Health and Society, University of Oslo, Oslo, Norway.
authors.forename: Mette
authors.initials: M
authors.lastname: Kalager
authors.affiliation: Institute of Health and Society, University of Oslo, Oslo, Norway.
authors.forename: Geir
authors.initials: G
authors.lastname: Hoff
authors.affiliation: Institute of Health and Society, University of Oslo, Oslo, Norway.
authors.forename: Michael
authors.initials: M
authors.lastname: Bretthauer
mesh_terms: D015746:Abdominal Pain / Q000209:etiology* / Q000517:prevention & control; D002245:Carbon Dioxide; D002432:Cecum; D003111:Colonic Polyps / Q000175:diagnosis; D003113:Colonoscopy / Q000009:adverse effects / Q000379:methods*; D005260:Female; D006801:Humans; D006993:Hypnotics and Sedatives / Q000008:administration & dosage; D007327:Insufflation / Q000379:methods*; D007441:Intubation, Gastrointestinal; D008297:Male; D008875:Middle Aged; D016037:Single-Blind Method; D014867:Water
chemical_list: D006993:Hypnotics and Sedatives; D014867:Water; D002245:Carbon Dioxide