Agreement between the ventilated capsule and the KuduSmart® device for measuring sweating responses to passive heat stress and exercise

ABSTRACT The present study assessed agreement between the KuduSmart® device and the ventilated capsule (VC) technique for measuring: i) minute-averaged local sweat rate (LSR); ii) sweating onset; iii) thermosensitivity; and iv) steady-state LSR, during passive heat stress and exercise. On two separate occasions for each heat stress intervention, participants were either passively heated by recirculating hot water (49°C) through a tube-lined garment until rectal temperature increased 1°C over baseline (n=8), or walked on a treadmill for 60 minutes at a fixed rate of heat production (n=9). LSR of the forearm was concurrently measured with a VC and the KuduSmart® device secured within ∼2 cm. Mean body temperature was calculated as the weighted average between rectal (80%) and mean skin (20%) temperature. Using a ratio scale Bland-Altman analysis with the VC as the reference, the KuduSmart® device demonstrated systematic bias for minute-averaged LSR (1.19 [1.09, 1.28]) and steady-state LSR (1.16 [1.09,1.23]), however no bias for thermosensitivity (1.08 [1.00, 1.16]) or sweating onset (1.00 [1.00, 1.00]). Although poor agreement was observed for minute-averaged LSR (CV = 43.3%), more than 73% of all observations with the KuduSmart® device (n=2795) were within an absolute error of < 0.2 mg/cm 2 /min to the VC. The KuduSmart® device demonstrated acceptable agreement for steady-state LSR (CV = 19.5%) and thermosensitivity (CV = 21.7%), and almost perfect agreement for sweating onset (CV = 0.14%). Collectively, the KuduSmart® device may be a satisfactory in-field solution for assessing the sweating response to heat stress.