FDA Expert Opines on Alleged Defect in Forced-Air Patient Warming System

Joseph O'Neill

Written by
— Updated on August 16, 2016

FDA Expert WitnessThis case involves a forced-air warming blanket placed over a patient during a total knee replacement surgery, which allegedly resulted in a deep tissue infection of the patient’s knee. The warming system in question functions by generating warm air in a standalone unit, which is then pumped through a plastic hose into the blanket, which is inflated. A series of small perforations on the underside of the blanket allows the continuous release of warm air into the area between the blanket and the patient’s exposed skin. Allegedly, when the warm air escapes from the space between the blanket and the patient’s skin, it is forced downward by the surgical drapes toward the floor. The warm air, now near the floor, then surges upward. This flow disrupts the downward laminar flow in the operating room, causing a draft that carries bacteria from the floor to the surgical site. It has also been suggested that the air is not sufficiently filtered by the warming device before it is sent to the warming blanket. It was alleged that the device was the cause of this particular patient’s infection, and that the device should have undergone closer scrutiny by the FDA through the agency’s 501(k) approval pathway.

Question(s) For Expert Witness

  • 1. Are you familiar with the approval process for this type of product?
  • 2. Will you be able to determine if this product was safe to bring to market?

Expert Witness Response E-053014

My understanding is that this would qualify as a 510(k) product, which entails a more rigorous approval process than that of its current classification (class 2). In order to determine what sort of scrutiny the device should have undergone before it was approved, it is standard practice to compare the product to others on the market to determine whether or not it is comparably safe and effective – this is the barometer used by the FDA to approve devices. A few questions which would help determine the safety of the device are as follows: What is the airflow rate for the blanket? Does this device have a pre-filter for the air blowing through it or is it connected to an air canister? What type of surgery suite were the majority of patients operated in (Trauma ICU, Orthopedic center, or regional hospital?)It  is important to note that not all surgery suites have a positive pressure or negative pressure classification, and airflow rates may vary depending on old, new, or renovated surgery centers. Typically, the airflow rate for a class II device would be minimal, since most surgeons may not want unclassified air blasting into the surgical sterile field. Most surgeons want a vacuum effect more than an  “A/C” effect during surgery.

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