Investigation of the HotDog patient warming system: detection of thermal gradients

Objective: To assess the performance of an active patient-warming device.

Materials and methods: Temperatures of an active patient-warming device (HotDog system) were measured at various time points using an infrared thermometer. The study was conducted in two phases: Phase 1 compared temperatures among four different areas of the warming blanket. Phase 2 compared conditions simulating different scenarios using a weighted patient simulator.

Results: Phase 1: Three out of four positions on the warming blanket had significantly different temperature measurements. Phase 2: Temperature output by the warming blanket was reduced: (1) in the absence of the patient simulator placed across the blanket (-1·9°C, P=0·013); (2) if the patient simulator was placed away from the blanket sensor (-2·0°C, P=0·009); and (3) if there was fluid between the patient simulator and warming blanket (-2·2°C, P=0·004). In a majority of measurements (95%), the set temperature of 43°C on the control unit was not reached (range, 29·8 to 42·9°C) and 2·3% of measurements were higher (range, 43·1 to 45·8°C) than the control unit set temperature of 43°C.

Clinical significance: Measured temperatures on the active warming blanket did not reflect control unit settings. This could result in the potential for hyperthermic injury, ineffectual heating and uneven heat distribution.