Patch-type Sensors On The Chest For Real-time Monitoring Of Core Temperature During Exercise In Heat

Athletes and workers are at risk of heat-related illness whenever they work for a prolonged duration in heat due to their metabolic demands. An increase in core body temperature (Tcore) is a leading indicator of heat-related illness, but a system that accurately measures Tcore using wearable devices has yet to be reported. A recently available patch-type sensor system, Moni-Patch® (Murata Manufacturing), uses the dual heat flux method to estimate Tcore. The patch sensor is attached to the skin of the upper chest using double-sided adhesive tape. PURPOSE: To validate a new wearable patch-type sensor system that predicts Tcore based on heat-flux data from the chest. METHODS: We conducted experiments that compared Moni-Patch temperatures (Tmoni) with the actual temperatures in both esophageal (Teso) and rectal (Trec) sites during exercise (walking, cycling, or arm-cranking) in various clothings (sports clothes, work clothes, or protective clothing) and environmental conditions (25-40 °C). Fifty-seven volunteers performed a 60-90 min exercise protocol including recovery. Tmoni was transmitted to a smartphone application that wirelessly received data from the patch-type sensors (65 × 45 × 8 mm) on the chest. RESULTS: Peak Teso and Trec during exercise reached from 38.0 °C to 39.5 °C in each protocol. The difference between Teso and Tmoni was -0.14 ± 0.18 °C and that between Trec and Tmoni was 0.04 ± 0.22 °C, using data sampled at 5-min intervals during exercise and recovery. The RMSEs were 0.25 ± 0.10 °C between Teso and Tmoni, and 0.24 ± 0.09 °C between Trec and Tmoni. The proportions of all paired measurements differing by less than the predefined threshold for validity of ≤0.3 °C were 81 ± 20% between Teso and Tmoni, and 83 ± 19% between Trec and Tmoni. CONCLUSIONS: These results indicate that the patch is capable of providing a moderate estimate of Tcore during acute exercise under heat conditions. The error ranges for the system are slightly superior to those in previous studies using non-invasive core temperature measurements. Supported by: The Japan Society for the Promotion of Science KAKENHI Grant-in-Aid for Scientific Research B 21H03347