title: Efficacy of forced-air warming systems with full body blankets.
abstract: OBJECTIVE
  Postoperative hypothermia after cardiac surgery is still a common problem often treated with forced-air warming. This study was conducted to determine the heat transfer efficacy of 11 forced-air warming systems with full body blankets on a validated copper manikin.
  
  
  METHODS
  The following systems were tested: 1) Bair Hugger 505; 2) Bair Hugger 750; 3) Life-Air 1000 S; 4) Snuggle Warm; 5) Thermacare; 6) Thermacare with reusable Optisan blanket; 7) WarmAir; 8) Warm-Gard; 9) Warm-Gard and reusable blanket; 10) WarmTouch; and 11) WarmTouch and reusable blanket. Heat transfer of forced-air warmers can be described as follows: Q = h x DeltaT x A. Where Q = heat flux (W), h = heat exchange coefficient (W x m-2 x degrees C-1), DeltaT = temperature gradient between blanket and manikin surface (degrees C), A = covered area (m2). Heat flux per unit area and surface temperature were measured with 16 heat flux transducers. Blanket temperature was measured using 16 thermocouples. The temperature gradient between blanket and surface (DeltaT) was varied and h was determined by linear regression analysis. Mean DeltaT was determined for surface temperatures between 32 degrees C and 38 degrees C. The covered area was estimated to be 1.21 m2.
  
  
  RESULTS
  For the 11 devices, heat transfers of 30.7 W to 77.3 W were observed for surface temperatures of 32 degrees C, and between -8.8 W to 29.6 W for surface temperatures of 38 degrees C.
  
  
  CONCLUSIONS
  There are clinically relevant differences between the tested forced-air warming systems with full body blankets. Several systems were unable to transfer heat to the manikin at a surface temperature of 38 degrees C.
authors.affiliation: Department of Anesthesiology, Emergency and Intensive Care Medicine, University of Göttingen, Robert-Koch-Str. 40, D-37075 Göttingen, Germany. abraeue@gwdg.de
authors.forename: Anselm
authors.initials: A
authors.lastname: Bräuer
authors.forename: Michael J M
authors.initials: MJ
authors.lastname: English
authors.forename: Nicolas
authors.initials: N
authors.lastname: Steinmetz
authors.forename: Nadja
authors.initials: N
authors.lastname: Lorenz
authors.forename: Thorsten
authors.initials: T
authors.lastname: Perl
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Weyland
authors.forename: Michael
authors.initials: M
authors.lastname: Quintel
mesh_terms: D001512:Bedding and Linens; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D006361:Heating; D006801:Humans; D007035:Hypothermia / Q000517:prevention & control*; D008348:Manikins; D011183:Postoperative Complications / Q000517:prevention & control*; D012881:Skin Temperature