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With dives lasting more than four minutes and reaching depths of more than 100 meters on a single-breath hold, freedivers test the limits of human endurance. Carnegie Mellon University researchers are part of an international team working on wearable biomedical technology that will enhance freediver safety, as well as provide fresh treatment insights for cardiac patients.
The smartwatch-like, wearable device uses light-emitting LEDs in contact with the skin to measure heart rate, blood volume and oxygen levels in the brain. It can withstand depths of at least 107 meters.
"Before now, understanding the effects on divers' neural and cardiovascular systems during deep dives was not possible, as research was focused only on simulated dives," said Erika Schagatay, a professor of animal physiology who is leading the project at Mid Sweden University. "Ultimately, the diver can reach a point where hypoxic (low oxygen) blackout occurs, and they need to be rescued. One of the main aims of our research is to warn both the diver and safety personnel of an imminent blackout."
As part of the group's research, published in Philosophical Transactions of the Royal Society B, existing, non-invasive technology called near-infrared spectroscopy (NIRS) was adapted to withstand the extreme pressure of deep dives in the open ocean.
"NIRS is a powerful tool, which has extensively been used for measuring brain function in healthy subjects, as well as clinical populations," said Jana Kainerstorfer (left), associate professor of biomedical engineering at Carnegie Mellon. "Recent advances in miniaturizing NIRS devices enabled measurements of brain function in more natural environments. The application of NIRS to study diving physiology is particularly exciting and will help us understand how brain function can be maintained under such extreme environmental conditions."
Studying how freedivers have conditioned themselves to tolerate bouts of extremely low oxygen and brain oxygen delivery could provide insights for pre-treatment (pre-conditioning) for surgical procedures. Perhaps the same procedures can be developed to improve protection of the brain and heart during cardiac surgery, and for post-conditioning therapeutic intervention after events such as a cardiac event.
"Beyond the exceptional physiological responses that freedivers display and the extremes they can tolerate, they may be a very informative physiological group," said lead researcher Chris McKnight, a research fellow at the University of St. Andrews. "Their physiological reactions are so unique and the conditions they're exposed to are not easily replicated, so they offer a unique way of understanding how the body responds to low blood oxygen, low brain oxygenation, and severe cardiovascular suppression."
University of St. Andrews is leading the collaboration with additional researchers from Mid Sweden, Carnegie Mellon and the University of Tokyo.
The international team is working on ways to warn both the diver and safety personnel of imminent blackouts.