title: Ex vivo testing of a temperature- and pressure-controlled amnio-irrigator for fetoscopic surgery.
abstract: BACKGROUND
  Currently, amnioinfusion fluids used in operative fetoscopy usually are preheated to body temperature. As the complexity of procedures increases, purposed designed devices should be designed that allow control of pressure and temperature during amnioinfusion or amnioexchange. In the current study, a prototype amnio-irrigator and fluid heater were evaluated.
  
  
  METHODS
  The medical fluid heater heats fluid by conduction up to 37 degrees C. The maximum irrigation pressure and flow rates can be preset. Actual irrigation pressure (0 to 30 mm Hg) and flow rate (0 to 300 mL/min) can be read on the front panel. A series of ex vivo experiments were set up to determine the relationship between the flow rate (FR) and lumen of the instruments as well as the maximum flow rate (MFR) with and without the pressure control. Further, the relationship between FR and the irrigation pressure (IP) was determined. In an artificial pseudoamniotic sac the relationship between FR and change in temperature was measured, with and without the use of the medical fluid heater.
  
  
  RESULTS
  When the IP was limited to 24 mm Hg, FR and pressure were correlated (r = 0.34; P <.001). The larger the functional lumen of the fetoscopic instrumentation, the higher the flow (r = 0.43; P <.001) and the lower the increase in IP (r = -0.47; P <.001). A quadratic relation between flow and temperature was observed both for preheated fluid as when using the fluid heater (r(2) = 0.71 and r(2) = 0.88; P <.001). However, at low flow rates, a thermal decrease of over 3 degrees C was observed when the fluid heater was not used.
  
  
  CONCLUSIONS
  The current study quantifies an expected relationship between the diameter of the irrigation channel and achievable flow rates. It also shows that a medical fluid heater is needed when strict control of temperature would be desired.
authors.affiliation: Centre for Surgical Technologies, Faculty of Medicine, Katholieke Universiteit Leuven, Leuven, Belgium.
authors.forename: Francesca
authors.initials: F
authors.lastname: Bonati
authors.forename: Alfredo
authors.initials: A
authors.lastname: Perales
authors.forename: Pavel
authors.initials: P
authors.lastname: Novak
authors.forename: Gerard
authors.initials: G
authors.lastname: Barki
authors.forename: Eduardo
authors.initials: E
authors.lastname: Gratacós
authors.forename: Umberto
authors.initials: U
authors.lastname: Nicolini
authors.forename: Jan A
authors.initials: JA
authors.lastname: Deprest
mesh_terms: D004867:Equipment Design; D020669:Fetoscopes; D005332:Fetoscopy / Q000379:methods*; D006358:Hot Temperature; D011312:Pressure; D012212:Rheology; D013696:Temperature; D007507:Therapeutic Irrigation / Q000295:instrumentation*