So, how long can you hold your breath?
One minute? Two minutes?
For graduate student Craig Steinback, the physiology behind this swimming pool game is driving his research, which one day could help treat individuals with sleep apnea.
This past year, the Health Sciences student spent time in Croatia where he studied free divers – individuals who participate in the extreme sport of competitive apnea. Competitors pursue great swimming depths or outrageous times or distances on a single breath without assistance from any breathing apparatus.
Under normal conditions, humans cannot store much oxygen in the body. During apnea there is no movement of the muscles of respiration and the volume of the lungs initially remains unchanged. Prolonged apnea leads to severe lack of oxygen in the blood circulation and a build up of carbon dioxide. Both situations need to be corrected, which is what causes stress in the body.
“During an apnea, whether it be with these divers or somebody with sleep apnea, it affects your sympathetic nervous system, or what can be called your fight or flight system,” says Steinback. “They both have a similar response during an apnea; both of their systems get jacked up, there’s all of this activity, blood pressure goes up. That’s kind of expected.”
What’s unexpected, adds Steinback, is the lack of any sort of affect on free divers, some of whom hold their breath for five minutes or longer.
“It doesn’t seem to affect them,” he says. “These individuals are interesting models in that we can study them and how they may not be affected the same way as sleep apnea people. The apneas themselves don’t seem to cause the cardiovascular consequences for the free divers that you see in those with sleep apnea, and when you consider the extreme nature of their sport that’s kind of surprising.”
Steinback is studying the divers to see what about their physiology is different and what allows them to do this without consequence.
“We can start to look at other factors that may predispose them to not being affected, whether it be genetic or lifestyle intervention,” says Steinback, noting his research is early in the discovery stage.
“From a sport aspect or exercise aspect, what is it and how do they end up doing it? What is it in their training? Is it a physiological change that allows them to do that, or is it a mental training aspect in the brain?”
Steinback will also look at whether these individuals later may develop some sort of pathology, keeping in mind that they are relatively young compared to the sleep apnea population.
“Anecdotally, we think that there may be a mental training aspect to it,” he says. “With some coaching … even the average person may be able to prolong how long they can hold their breath.”
Down the road, Steinback feels there is potential to apply his work to those affected with sleep apnea.
“I don’t think we’re at the point where we’re going to be applying this directly to sleep apnea patients, but I think we can perhaps make some leaps of logic that if there is a genetic component or training component, that perhaps those types of things can then apply to a sleep apnea patient down the road in treatment.”
Steinback is in the final stages of his PhD training in the Neurovascular Research Lab under the mentorship of Kevin Shoemaker. His study abroad was hosted by the Split School of Medicine in Croatia and funded by NSERC’s Michael Smith Foreign Study Supplement program.