SEASPOT, a System using Electrodermal Activity Sensing to Predict Oxygen Toxicity

Triton’s System using Electrodermal Activity Sensing for the Prediction of Oxygen Toxicity, SEASPOT, is a novel wearable sensor with on-board real-time signal processing capabilities to predict seizure likelihood and to provide a symptom onset warning to the wearer, especially for divers. Breathing hyperbaric oxygen (HBO2) is used during military and recreational diving operations, during HBO2 therapy for treating problematic wounds, and as an effective treatment for decompression sickness where the ensuing large partial pressure gradient for nitrogen diffusion from tissues-to blood-to alveolar gas promotes removal of nitrogen from the body through pulmonary ventilation. Additionally, prebreathing 100% oxygen prior to decompression has been shown to effectively mitigate DCS. The use of HBO2 in these situations is limited by an increased risk of developing central nervous system oxygen toxicity (CNS-OT). CNS-OT is characterized by enhanced autonomic activity and abnormal cardiorespiratory changes that can present via early symptoms that can impair performance including headache, nausea, tinnitus, lip twitching, cognitive effects, and tingling of the limbs. Ultimately CNS-OT can culminate in generalized tonic–clonic seizures and loss of/altered consciousness followed by cardiogenic pulmonary edema. Losing consciousness and/or convulsing under water could result in dislodgement of a diver’s gas supply from his or her mouth and could lead to drowning. Likewise, losing consciousness and convulsing for patients undergoing HBO2 therapy could result in further injuries. Previous studies have suggested that electrodermal activity (EDA) can be used to predict seizures. Physiologically, elevated sympathetic activity associated with augmented seizure in human activity occurs at 1 ATA when breathing air with the risk for developing seizures increasing during protracted breathing of >2.5–3.0 ATA O2. Because seizure occurrence risk due to CNS-OT varies from person-to-person and dive-to-dive, conservative dive tables have been developed limiting maximum safe depth and dive duration. If CNS-OT symptoms can be predicted, the risk to divers could be reduced by personalizing their safe exposure limits for HBO2 at depth and by allowing them to adjust their depth and gas mixtures preemptively. In other words, by predicting the onset of CNS-OT symptoms, Triton’s SEASPOT device will allow divers to dive deeper, longer, and safer. This proposal describes Triton Systems’ approach to developing, demonstrating, and validating a small, sealed unit with integrated electrodermal activity (EDA) sensing electrodes, battery, and alerting capability in a wearable form factor. Our device will process EDA signals in real time using algorithms that have been shown to predict seizure onset and will alert users, especially divers, of potential oxygen toxicity issues in time to prepare for and possibly avert the most severe oxygen toxicity consequences