Graydon Raymer makes people breathe heavy and gets hearts beating faster. It’s all in the name of research that could one day save a life or help an elite athlete reach new records.
Raymer, an associate professor in the Bachelor of Physical Health and Education program at Nipissing University, is investigating how the heart and lung systems work together during exercise and at rest.
“Ultimately, my goal is to study the fundamental mechanisms controlling and limiting oxygen use during exercise,” Raymer says. “I am trying to identify factors that promote more efficient use of oxygen in health and disease.”
During physical activity, the ventilation of the lungs increases to allow the necessary exchange of oxygen and carbon dioxide. Simultaneously, cardiac output increases to circulate the newly oxygenated blood to the active muscles. At rest, cardiac output and ventilation are closely matched, so the work the heart and respiratory muscles must perform is minimized. During exercise a mismatch occurs, reducing the cardiovascular system’s efficiency and forcing the lungs to work harder to absorb oxygen and remove carbon. This mismatching of cardiac output to ventilation is thought to contribute to both healthy and diseased individual’s ability to perform exercise in any capacity.
To collect data, Raymer observes people at rest and during exercise using electrocardiography to measure heart rhythm, spirometry to measure breathing rhythm, a metabolic cart to measure whole-body oxygen consumption, and near-infrared spectroscopy to measure oxygen levels in tissue. He then applies mathematical modeling to the data to detect changes in rate, frequency and variability, with particular interest in how the different cardiovascular parameters may be interrelated.
On one hand, Raymer’s research matters to healthy people, even elite athletes, because it is unclear when and why ventilation and cardiac output become mismatched during exercise and how that contributes to muscle fatigue. On the other hand, his research matters to a number of clinical populations as reduced cardio-ventilatory coupling is the hallmark of many cardiovascular diseases, and cardiac inefficiency might partly account for increased mortality.
Raymer’s research may support a therapeutic benefit of cardiac pacemakers with feedback functions that match heart rhythm with breathing rhythm.