title: In vitro calibration of a system for measurement of in vivo convective heat transfer coefficient in animals.
abstract: BACKGROUND
  We need a sensor to measure the convective heat transfer coefficient during ablation of the heart or liver.
  
  
  METHODS
  We built a minimally invasive instrument to measure the in vivo convective heat transfer coefficient, h in animals, using a Wheatstone-bridge circuit, similar to a hot-wire anemometer circuit. One arm is connected to a steerable catheter sensor whose tip is a 1.9 mm x 3.2 mm thin film resistive temperature detector (RTD) sensor. We used a circulation system to simulate different flow rates at 39 degrees C for in vitro experiments using distilled water, tap water and saline. We heated the sensor approximately 5 degrees C above the fluid temperature. We measured the power consumed by the sensor and the resistance of the sensor during the experiments and analyzed these data to determine the value of the convective heat transfer coefficient at various flow rates.
  
  
  RESULTS
  From 0 to 5 L/min, experimental values of h in W/(m2.K) were for distilled water 5100 to 13000, for tap water 5500 to 12300, and for saline 5400 to 13600. Theoretical values were 1900 to 10700.
  
  
  CONCLUSIONS
  We believe this system is the smallest, most accurate method of minimally invasive measurement of in vivo h in animals and provides the least disturbance of flow.
authors.affiliation: Department of Electrical Engineering, Chulalongkorn University Phaya-Thai Road, Bangkok 10330, Thailand. tchanchana@yahoo.com
authors.forename: Chanchana
authors.initials: C
authors.lastname: Tangwongsan
authors.forename: Louay
authors.initials: L
authors.lastname: Chachati
authors.forename: John G
authors.initials: JG
authors.lastname: Webster
authors.forename: Patrick V
authors.initials: PV
authors.lastname: Farrell
mesh_terms: D000818:Animals; D015374:Biosensing Techniques; D002138:Calibration; D017115:Catheter Ablation / Q000379:methods*; D017097:Electric Impedance; D004563:Electrochemistry; D004867:Equipment Design; D006358:Hot Temperature; D066298:In Vitro Techniques; D008099:Liver / Q000473:pathology*; D015233:Models, Statistical; D009206:Myocardium / Q000473:pathology*; D010984:Platinum / Q000737:chemistry; D013696:Temperature; D013814:Thermal Conductivity; D014867:Water
chemical_list: D014867:Water; D010984:Platinum