Elite freedivers have brain oxygen levels lower than seals

Credit: University of St AndrewsNew research from the University of St Andrews shows that elite freedivers, who dive in open sea unaided, have brain oxygen levels that are even lower than seals during deepest dives.Divers reached depths up to 107 meters and experienced brain oxygen levels that could normally cause unconsciousness. They also had heart rates similar to those of dolphins, seals, and whales in the water.These new findings were published today in Philosophical Transactions of the Royal Society. They are being used to help scientists understand the physiology of marine mammal.It may provide information about how freedivers have been conditioned to tolerate periods of very low oxygen. This could help to understand pre-conditioning (pre-conditioning for surgery)These surgical procedures could be developed to enhance brain and heart protection during cardiac surgery and post-conditioning therapy after cardiac events.Mid Sweden University's Project Leader, Professor Erika Schagatay said that she has been researching freediving for over 30 years. She stated: "Before this, understanding the effects of these exceptional divers brains and cardiovascular system during such deep dives, as well as just how far these human beings push their bodies, was impossible because all research was conducted during simulated dives at the lab.Credit: University of St AndrewsThe diver may reach a point of hypoxic (low oxygen), blackout, at which point the diver must be rescued. The research aims to alert the diver and the safety personnel about an imminent blackout.A device similar to a smartwatch, it uses light emitting LEDs to contact the skin to measure heart rate, blood volume, and oxygen levels. The system was developed by a team of researchers from the University of St Andrews and Mid Sweden University.This wearable biomedical technology measures the physiological function of elite athletes at depths of at most 107m.Freediving is one of the most extreme and elite sports in the world. Freedivers can dive for more than four minutes, reach depths greater than 100m in a single breath-hold and last more than four hours.Dr. Chris McKnight from the University of St Andrews' Sea Mammal Research Unit, SMRU, is the lead researcher. He said that the divers displayed exceptional physiological responses during dives."We measured heart rate at 11 beats per min and blood oxygenation levels at 98 percent. This is much lower than the 50 percent threshold at which people are likely to lose consciousness. It's also equivalent to the lowest values at the summit of Mount Everest."Credit: University of St AndrewsResearchers at the University of St Andrews modified an existing non-invasive human biomedical technology device using near-infrared spectrum (NIRS) that was developed by Dutch collaborators Artinis Medical Systems to withstand the extreme pressure of deep diving in the open ocean.Steve Balfour, SMRU Instrumentation University of St Andrews' lead engineer on this project, stated: "It's amazing to be involved in such a challenging engineering project.It's worth the sleepless nights to see the end product descend to such depths and return unique data.Dr. McKnight said that "beyond their exceptional physiological reactions and the extremes they can endure, they may also be a very informative physiological groups. Because their physiological responses are unique, and they are exposed to conditions that are difficult to replicate, they provide a unique insight into how the body reacts to low blood oxygen and low brain oxygenation."Our instrument allows us to now study unique physiological reactions while these amazing athletes do their maximum performances."Jana Kainerstorfer is the director of Carnegie Mellon University's Biophotonics Lab. She said that NIRS is an extremely powerful tool that can be used to measure brain function in healthy subjects and clinical populations.Recent advances in miniaturizing NIRS have allowed measurements of brain function within more natural environments. The use of NIRS in diving physiology research is particularly exciting. It will allow us to understand how brain function can survive extreme environmental conditions.Learn more Wearable device shows how seals prepare to diveAdditional information: J. Chris McKnight and co., When the human mind goes diving: using near infrared spectrum to measure cerebral, systemic, and cardiovascular responses to deep, breathe-hold diving by elite freedivers. Philosophical Transactions of the Royal Society, B: Biological Sciences (2021). Information from the Journal: Philosophical Transactions of the Royal Society, B J. Chris McKnight and co, When the human mind goes diving: Using near-infrared spectrum to measure cerebral & systemic cardiovascular responses to deep breath-hold diving by elite freedivers. (2021). DOI: 10.1098/rstb.2020.0349