Human Physiology Theses and Dissertations

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Browsing Human Physiology Theses and Dissertations by Author "Bradbury, Karleigh"

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    Influence of a Patent Foramen Ovale and Biological Sex on Thermoregulatory and Cardiovascular Responses at Rest and during Exercise
    (University of Oregon, 2024-08-07) Bradbury, Karleigh; Lovering, Andrew
    In healthy humans, core temperature (Tc) is maintained within narrow limits around ~37 °C. There is interindividual variability in resting Tc with most individuals between 36 and 37°C. Many factors contribute to the variability in the resting Tc including but not limited to, differences in basal metabolic rate, circadian rhythm differences, levels of inflammatory markers or endogenous pyrogens (i.e. tumor necrosis factor (TNF), interleukin (IL)-1, IL-6, interferons), and menstrual cycle phase. Previous findings have also suggested that the presence of a patent foramen ovale in young, healthy men may be associated with elevations in resting esophageal temperature (Tesoph) that exist during thermal stressors (exercise, hot water immersion, cold water immersion). However, whether this difference in temperature exists in women with a PFO or whether this elevation in temperature is caused by differences in metabolic heat production are unknown. Additionally, while the elevations in temperature have been seen in a lab setting, whether the elevation in temperature influences self-paced 5k performance of thermoregulation during SCUBA diving is unknown. In Chapter IV, we demonstrated that during 60 min of exercise at a controlled heat production (7 w/kg) that men without a PFO have higher Tc compared to men with a PFO. However, there was no difference in the change in Tc over the course of the hour, suggesting that although there may be variability in the baseline temperatures among individuals, the presence or absence or a PFO does not influence mechanisms of thermoregulation during exercise. Additionally, no difference in baseline or exercise Tc or Tesoph existed between women with and without a PFO. In addition to Tc & Tesoph, we measured skin temperature, mean body temperature, heart rate and respiratory heat loss. There were no differences in any of these variables between PFO- and PFO+ groups. In Chapter V, we showed that men with a PFO have a greater increase in Tc despite slower running times compared to men without a PFO. However, contrary to our hypothesis and unlike previous studies, men with a PFO did not have higher baseline Tc. The greater increase in Tc during the 5k may be due to differences in heat production, time for heat storage (longer running times), differences in body composition/body weight or variability in ambient conditions. There were no differences in Tc or 5k performance between PFO+ and PFO- women. Finally, in Chapter VI, we demonstrated that the presence of a PFO had no effect on baseline or post-SCUBA diving core temperatures. We demonstrated that the most impactful predictors of the change in core temperature during a SCUBA dive were related to anthropometric characteristics such as body mass, body mass index, body surface area/mass ratio and wetsuit thickness.This dissertation includes previously unpublished material.