This case involves a man who was admitted for a gastric bypass and in preparation for the operation, a Snuggle Warm Blanket System was applied to his chest/upper body. At the end of the procedure, the warmer was removed and it was discovered that the patient had suffered 1st and 2nd degree burns to the area where the warmer had been placed. The anesthesiologist denies that any alarm on the device sounded to alert him that the blanket was too hot. The attorney retained a biomedical engineering expert with warming blanket design experience to evaluate the case.
Question(s) For Expert Witness
- 1. Under what conditions would a warming blanket's alarm have not sounded despite the device becoming too hot?
Expert Witness Response E-125500
This is similar to the reasons why a lightbulb may not turn on. Clearly the blanket was receiving power or it would not have been able to generate heat. First, a short in a wire leading to the alarm could have occurred. This could be for several reasons – an internally disconnected wire (either through manufacturing or from previous use). It also could be that the seal on the blanket could have been compromised and if any fluid entered the circuitry it could act as a short. Second, if the wrong resistance (or capacitance) value was present in the circuitry the alarm volume could be decreased, making it difficult or impossible to hear. Third, the alarm itself could have been compromised. Lastly, depending upon the pad, if the alarm was placed against the patient it is possible that it was not heard because it was muffled against their body.
Expert Witness Response E-125516
The warming blanket would require a thermocouple reading of the air temperature into the blanket along with an air flow rate into or out of the blanket; if the thermocouple was improperly calibrated, the air temperature could have been too high causing a burn; if the air flow rate out of the blanket were too low due to obstruction in the air path, then the blanket temperature will equal the air inlet temperature throughout the blanket including sensitive areas of the patient skin causing a skin burn; the blanket could have been wrapped around the patient too tightly in places thus not allowing for escape of patient metabolic heat generation resulting in temperatures higher than the blanket temperature and skin burning.