Grant: Discovery Grants Program - Individual

My NSERC-supported research program contributes to the training of exceptional HQP through exploring the complex dynamic physiological adaptations of the cardiorespiratory and cerebrovascular systems to challenges typical of daily life. Our basic research and spaceflight studies have been cited more than 20,000 times and received international awards and national honours. We will continue to develop our influential research on oxygen uptake dynamics by applying artificial intelligence interpretation of wearable sensor data to accurately predict metabolic rate and fitness indicators. Collection of sensor data and "ground-truth" laboratory standards during a 60-day bed rest study in France, and in 9 astronauts before, during and after 6-month spaceflights in our Vascular Aging study will provide HQP rich data sets to mine and explore novel cardiorespiratory indicators related to exercise countermeasures employed during these studies. From our knowledge of regulation of blood flow to working skeletal muscles, we will extend applications of near infrared spectroscopy to monitor changes in perfusion and oxygenation of the tibial bone. My HQP will be the first to study bone perfusion during walking and will explore control mechanisms by manipulating perfusion pressure and vasoconstriction during plantar flexion exercises. We will extend our previous research on cerebral blood flow (CBF) when new trainees are recruited to complete two main projects. The pattern of increase in CBF at the onset of exercise is very poorly described and the mechanisms underlying the increase are incompletely understood. We will apply modeling techniques developed in our study of oxygen uptake kinetics to the increase in CBF. Then we will tease out relative contributions of changes in arterial blood pressure (BP) and CO2 to the increase in CBF by altering arterial CO2 and by regulating breathing patterns, and by manipulating arterial BP. Applying our two-breath method we will determine the gain of the CBF responses to BP and CO2 then predict the change in CBF for comparison to measured CBF to identify regulating factors. During postural tilt, CBF decreases to the point of fainting. This decrease is linked to a fall in arterial BP, but we previously reported that CBF starts to decrease before BP and was related to a drop in arterial CO2, a potent regulator of CBF, yet researchers have argued that fainting is not related to CO2. We see a "chicken and egg" question here, does the drop in CO2 cause a drop in CBF, or does the drop in CBF cause the drop in CO2. We hypothesize the latter and propose experiments in which we manipulate CBF by reducing cardiac output in a random manner to provide time series data that will allow us to apply methods to achieve causal solutions of which occurs first. These results will have a large impact on basic understanding of CBF and could provide important information for many people who experience what are referred to as unexplained falls.