Skin temperature of the knee was effectively reduced when using a new continuous cold-flow cryocompression device: a randomised controlled crossover trial

Objective: To determine which temperature settings on a new continuous cold-flow cryocompression device effectively reduce knee skin temperature to 10–15 °C, where pain and swelling are expected to be attenuated. Design: Randomised controlled crossover trial. Setting: University laboratory. Participants: 32 healthy adult participants recruited (1 dropout) with no contraindications to cryocompressive therapy. Intervention: A k-type thermocouple was used to record skin temperature at baseline and every five minutes during a 30-minute cryocompression treatment in a control condition and when using four different device temperature settings (6 °C, 8 °C, 10 °C, and 12 °C) on a continuous cold-flow cryocompression device. Conditions were labelled Control, Con-6, Con-8, Con-10, and Con-12, respectively. Main outcome measures: Skin temperature change (°C) throughout cryocompression; time taken (mins) to achieve skin temperature < 15 °C; and the difference between final skin temperature and device temperature setting (°C). Results: Median (IQR) skin temperature after cryocompression was 32.1 °C (29.3–33.4), 12.8 °C (12.1–14.6), 14.3 °C (13.8–15.7), 16.1 °C (15.2–17.3), and 17.7 °C (16.9–18.9) for the Control condition and Con-6, Con-8, Con-10 and Con-12, respectively. It took 20 min (Con-6) and 25 min (Con-8) for skin temperature to reach < 15 °C. A median (IQR) difference of 6.8 °C (6.1–8.6), 6.3 °C (5.8–7.7), 6.1 °C (5.2–7.3), and 5.7 °C (4.9–6.9) for Con-6, Con-8, Con-10, and Con-12, respectively was observed between device temperature setting and final skin temperature. Conclusions: The device is recommended as it reduced skin temperature to the therapeutic range of 10–15 °C during a 30-minute treatment when using the 6 °C or 8 °C device temperature settings. Future research should determine optimal treatment lengths for cryocompression. Contribution of the Paper: • The Physiolab S1 cryocompression device allows users to determine precise temperatures of the ice-water that is circulated around the knee during a treatment. • This paper demonstrates the ability of each temperature setting to reduce skin temperature around the knee to within the target therapeutic range of 10–15 °C. • There is a significant discrepancy between the temperature setting of the device and the skin temperature achieved during a treatment. • Clinicians should not assume that all temperature settings on this and similar devices sufficiently reduce skin temperature of the knee to confer a therapeutic benefit.