Effects of Parallel Contact Cooling on Pulsed-Type, Bipolar Radiofrequency-Induced Tissue Reactions in an in vivo Porcine Model.

Background: Skin cooling during laser or radiofrequency (RF) treatments is a method to minimize thermal damage to the epidermis, reduce pain, and decrease post-treatment downtime. We evaluated the effect of parallel contact cooling (PCC) on RF-induced thermal reactions in minipig skin in vivo after bipolar microneedling RF treatment.

Methods: RF treatments were administered at frequencies of 0.5, 1, and 2 MHz with single (500 ms), six (1000 ms), and ten (5000 ms) sub-pulse packs to minipig skin with or without PCC. Subsequently, thermometric imaging and histology were used to analyze skin reactions to RF.

Results: Thermometric images showed that PCC promptly lowered skin temperature in the RF-treated area, with this effect persisting for over 60s. Regardless of the PCC, RF treatments lasting for 500 ms with a single pulse pack resulted in peri-electrode coagulative necrosis (PECN) zones and inter-electrode non-necrotic thermal reaction (IENT) zones in the dermis. In contrast, treatment lasting 5000 ms with 10 sub-pulse packs produced distinct IENT without notable PECN over a wide dermal area. Skin specimens obtained at 1 h and 3, 7, and 14 days after PCC-assisted RF treatments showed a higher degree of thermal tissue reactions in the deeper dermal regions compared to those after RF treatments without PCC.

Conclusion: PCC-assisted RF treatment, utilizing an invasive bipolar microneedling device, enhanced RF-induced skin reactions in the mid to deep dermis while preserving the epidermis and upper papillary dermis from excessive thermal tissue injury.