title: Current limitations in endoscopic CO₂ insufflation for NOTES: flow and pressure study.
abstract: BACKGROUND
  Natural orifice transluminal endoscopic surgery (NOTES) requires fast and steady CO₂ insufflation into the intraluminal and intra-abdominal spaces through a flexible endoscope. However, an optimal endoscopic insufflation system has yet to be determined.
  
  
  OBJECTIVE
  To verify the performances of 2 currently available CO₂ insufflators in an experimental NOTES setting: (1) an automatic pressure-regulated surgical insufflator (UHI-3) and (2) a manual endoscopic insufflator (UCR).
  
  
  METHODS
  An inanimate bench study followed by an acute animal experiment.
  
  
  METHODS
  Osaka University and Olympus Research and Development Department.
  
  
  METHODS
  The UHI-3 or UCR was connected to an endoscope of differing length and diameter via an insufflating line of differing length and diameter. The flow rates at the tip of the endoscope (bench test), the time to establish pneumoperitoneum, and the time to re-establish pneumoperitoneum after forceful suction (porcine model) were obtained.
  
  
  RESULTS
  The UHI-3 failed to feed CO₂ through an insufflating channel but fed CO₂ via a working channel but required a large channel (>3 mm) and a wide insufflating line (>7 mm) to accomplish an acceptable flow rate. UCR fed CO₂ through the insufflating channel; however, the time taken to establish pneumoperitoneum and the time taken to re-establish pneumoperitoneum after forceful suction were longer compared with the time taken for UHI-3 insufflation via the working channel or laparoscopic cannula.
  
  
  CONCLUSIONS
  Bench/animal study with small sample numbers; no human trial.
  
  
  CONCLUSIONS
  The currently available CO₂ insufflators are not optimal for NOTES. Modification of an endoscopic insufflation system and/or development of a dedicated overtube with an insufflating function are therefore essential.
authors.affiliation: Department of Surgery, Osaka University Graduate School of Medicine, Yamadaoka, Osaka, Japan. knakajima@gesurg.med.osaka-u.ac.jp
authors.forename: Kiyokazu
authors.initials: K
authors.lastname: Nakajima
authors.forename: Toshirou
authors.initials: T
authors.lastname: Nishida
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Milsom
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Takahashi
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Souma
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Miyazaki
authors.forename: Hideki
authors.initials: H
authors.lastname: Iijima
authors.forename: Masaki
authors.initials: M
authors.lastname: Mori
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Doki
mesh_terms: D000818:Animals; D020776:Endoscopes, Gastrointestinal; D016099:Endoscopy, Gastrointestinal; D004869:Equipment Safety; D005260:Female; D006801:Humans; D007327:Insufflation / Q000295:instrumentation*; D023421:Models, Animal; D008954:Models, Biological; D057605:Natural Orifice Endoscopic Surgery / Q000295:instrumentation*; D011028:Pneumoperitoneum, Artificial / Q000295:instrumentation*; D015203:Reproducibility of Results; D012212:Rheology; D013552:Swine