H. Feldmeier1, K.E. Bradbury1-3, A.W. Betts1, E.M. Castillo1, T. Kelly1, N. Charkoudian2, A.T. Lovering1

1University of Oregon, Eugene, OR; 2United States Army Research Institute of Environmental Medicine, Natick, MA; 3ARCS Program, Oregon Chapter

During exercise, core (Tc) and skin temperatures (Tsk) increase due to a higher heat production from increased metabolism by exercising muscles. To maintain Tc and Tsk within a precise range the body increases skin blood flow to facilitate heat loss from radiation and sweating, and there is some heat released through exhalation. Individuals with a patent foramen ovale (PFO) do not release as much heat through respiration as individuals without a PFO because a fraction of their cardiac output bypasses the respiratory system (Davis et al. 2017). PURPOSE: The purpose of this study was to determine if the presence of a PFO is associated with higher Tc and Tsk at rest and during exercise in healthy adult men. METHODS: The study was completed in a thermoneutral environment (20 C, 39% rh). 21 men (11 PFO+ and 10 PFO-), ages 18-35 y/o completed the study. Participants completed 3 study visits. On day 1 they performed non-invasive pulmonary function tests and a cardiac ultrasound to determine the presence or absence of a PFO. On day 2, participants performed a graded exercise protocol at 4 workloads to determine what workload would elicit a heat production of 7 W/kg of body weight. They also completed a peak test. On visit 3, participants completed a 1 hour cycling protocol at the previously determined 7W/kg workload, which was confirmed using metabolic data during the 1 hr bout. Tc (telemetric pill) and Tsk (skin thermistors on 4 sites) were measured continuously. RESULTS: PFO- participants had significantly higher (P<0.05) Tc before and during exercise compared to PFO+ subjects (rest PFO- , rest PFO+ ) (exercise PFO- , exercise PFO+ ). No significant difference was observed in Tsk between PFO+ and PFO- participants. CONCLUSION: Contrary to our previously published work, these data suggest that the presence of a PFO is associated with decreased Tc at rest and during exercise. Reasons for these discrepancies are not yet understood.

Supported by the University of Oregon Human Physiology Department, the Human Physiology Excellence Fund, and USARIEM.

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