What determines the efficacy of forced-air warming systems? A manikin evaluation with upper body blankets.
BACKGROUND
Forced-air warming has gained acceptance as an effective means to prevent perioperative hypothermia. However, little is known about the influence of air flow and air temperature at the nozzle and the influence of heat distribution in the blankets on the efficacy of these systems.


METHODS
We conducted a manikin study with heat flux transducers using five forced-air warming systems to determine the factors that are responsible for heat transfer from the blanket to the manikin.


RESULTS
There was no relation between air temperature at the nozzle of the power unit and the resulting heat transfer. There was also no relation between the air flow at the nozzle of the power unit and the resulting heat transfer. However, all blankets performed best at high air flows above 19 L/s. The heat exchange coefficient, the mean temperature gradient between the blanket and the manikin correlated positively with the resulting heat transfer and the difference between the minimal and maximal blanket temperature correlated negatively with the resulting heat transfer.


CONCLUSIONS
The efficacy of forced-air warming systems is primarily determined by the blanket. Modern power units provide sufficient heat energy to maximize the ability of the blanket to warm the patient. Optimizing blanket design by optimizing the mean temperature gradient between the blanket and the manikin (or any other surface) with a very homogeneous temperature distribution in the blanket will enable the manufacturers to develop better forced-air warming systems.
Bräuer
Anselm
A
Department of Anesthesiology, University of Göttingen, Göttingen, Germany. abraeue@gwdg.d
Bovenschulte
Henning
H
Perl
Thorsten
T
Zink
Wolfgang
W
English
Michael John Murray
MJ
Quintel
Michael
M
D000388:Air; D001512:Bedding and Linens; D004867:Equipment Design; D006361:Heating / Q000295:instrumentation*; D006801:Humans; D007035:Hypothermia / Q000517:prevention & control*; D008348:Manikins; D008962:Models, Theoretical; D017694:Rewarming / Q000295:instrumentation*; D013696:Temperature; D013816:Thermodynamics