Detecting hypoxia through the non-invasive monitoring of sweat lactate and tissue oxygenation

Hypoxia is the state of insufficient tissue blood oxygenation that causes tissue damage and even organ failure. Accurate and timely methods for detecting hypoxia are critically needed. To address this need, a wearable device for the non-invasive and simultaneous detection of sweat lactate and tissue oxygenation levels is developed. The integrated device consists of a hydrogel for colourimetric sweat lactate sensing and optical electronics. Both tissue oxygenation and the colourimetric changes of the hydrogel were optically read out quantitatively and concurrently over the same skin area. Prototype devices were tested on an optical phantom with artificial and real sweat samples, validating its capability to measure these two indicators independently and without interference. Finally, the device was demonstrated to be capable of real-time "on-body" simultaneous monitoring of sweat lactate spikes and tissue oxygenation drops (StO2), which showed strong correlation during a hypoxia protocol.The novel device can be applied in broad clinical and non-clinical settings including post-operative care and measuring athlete endurance in a cost-effective manner.