Monitoring Wound Health through Bandages with Passive LC Resonant Sensors.

This paper details a passive, inductor-capacitor (LC) resonant sensor embedded in a commercial dressing for low-cost, contact-free monitoring of a wound; this would enable tracking of the healing process while keeping the site closed and sterile. Spiral LC resonators were fabricated from flexible, copper-coated polyimide and interrogated using external reader antennas connected to a two-port vector network analyzer; the forward transmission scattering parameter (S21) magnitude was collected, and the resonant frequency (MHz) and the peak-to-peak amplitude of the resonant feature were identified. These increase during the healing process as the permittivity and conductivity of the tissue change. The sensor was first tested on gelatin-based tissue-mimicking phantoms that simulate layers of muscle, blood, fat, and skin at varying phases of wound healing. Finite element modeling was also used to verify the empirical results based on the expected variations in dielectric properties of the tissue. The performance of the resonant sensors for in vivo applications was investigated by conducting animal studies using canine patients that presented with a natural wound as well as a controlled cohort of rat models with surgically administered wounds. Finally, transfer functions are presented that relate the resonant frequency to wound size using an exponential model (R2 = 0.58-0.96). The next steps in sensor design and fabrication as well as the reading platform to achieve the goal of a universal calibration curve are then discussed.

Type III Hypersensitivity Reaction to Subcutaneous Insulin Preparations in a Type 1 Diabetic.

Management of type 1 diabetes in patients who have insulin hypersensitivity is a clinical challenge and places patients at risk for recurrent diabetic ketoacidosis (DKA). Hypersensitivity reactions can be due to the patient's response to the insulin molecule itself or one of the injection's non-insulin components. It is therefore crucial for clinicians to quickly recognize the type of hypersensitivity reaction that is occurring and identify potentially immunogenic additives for the purpose of directing therapy as various insulin preparations have differing ingredients. We present the case of a 23-year-old diabetic female with common variable immunodeficiency (CVID) and autoimmune enteropathy who developed a type III hypersensitivity reaction to multiple formulations of subcutaneous insulin after years of use and the challenges of devising a long-term management strategy.