title: Effect of hyperbarism on radiofrequency ablation outcome.
abstract: OBJECTIVE
  Our objective was to investigate whether increases in atmospheric or local tissue pressure would affect the outcome of radiofrequency ablation procedures and the size of the created thermal lesions.
  
  
  METHODS
  Thermal lesions were produced in specimens of explanted bovine liver inside a hyperbaric chamber at 101 (atmospheric), 141, 202, 273, and 364 kPa using radiofrequency power settings of 20, 30, 40, and 50 W. In subsequent in vivo experiments, thermal lesions were produced in the livers of anesthetized pigs with or without occlusion of the hepatic vein draining the ablation site.
  
  
  RESULTS
  At each radiofrequency power setting, progressive increases in applied pressure were paralleled by decreases in minimum impedance and increases in maximum tissue temperatures at the electrode tip (reflecting tissue-fluid boiling points), delivery time, total energy delivered, and thermal lesion volumes. Similar increases were observed in radiofrequency ablation procedures performed in vivo under occlusion of the vein draining the ablation site.
  
  
  CONCLUSIONS
  By elevating the tissue-fluid boiling point, increased pressure delays the desiccation of tissue in contact with the radiofrequency electrode tip and the related sharp increase in impedance. The result is prolonged delivery of larger amounts of radiofrequency energy and larger thermal lesions.
authors: VI Department of Internal Medicine, Policlinico San Matteo Foundation, IRCCS, Piazzale Golgi, no.1, 27100 Pavia, Italy. s.rossi@smatteo.pv.it
authors: Sandro
authors: S
authors: Rossi
authors: Mario
authors: M
authors: Gallati
authors: Laura
authors: L
authors: Rosa
authors: Amedeo
authors: A
authors: Marini
authors: Francesca Torello
authors: FT
authors: Viera
authors: Marcello
authors: M
authors: Maestri
authors: Paolo
authors: P
authors: Dionigi
mesh_terms: D000818:Animals; D001831:Body Temperature; D017115:Catheter Ablation / Q000379:methods*; D002417:Cattle; D004735:Energy Transfer / Q000502:physiology; D006498:Hepatectomy / Q000379:methods*; D066298:In Vitro Techniques; D008099:Liver / Q000502:physiology* / Q000601:surgery*; D011312:Pressure; D016896:Treatment Outcome