Association of Patent Foramen Ovale with Respiratory Heat Loss at Rest and During Exercise in Men
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Date
2023-04
Authors
Castillo, Elizabeth
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
During exercise, approximately 10-14% of heat loss occurs via respiration, termed respiratory heat loss (RHL). RHL involves components of both evaporative (Eres) and convective (Cres) heat loss from the upper respiratory tract. Previous research has shown that men with a patent foramen ovale (PFO) have higher core temperatures (Tc) at rest and during exercise. It is unknown whether differences in RHL contribute to the differences seen in Tc between PFO+ and PFO- men. PURPOSE: The purpose of the study was to test whether there are differences in RHL (Eres, Cres, and total RHL (Tres)) between PFO+ and PFO- men at rest and during 60 min of exercise at a workload eliciting a heat production (Hprod) of 7 W/kg. METHODS: Twenty-one healthy males (11 PFO+, 10 PFO-, 18-36 y/o) participated in the study. Visit 1 included an ultrasound screening to test for the presence or absence of a PFO and lung function testing. Visit 2 involved a graded exercise protocol to determine the workload that would elicit a heat production of 7 W/kg, followed by a VO2peak test. During the graded exercise protocol, subjects cycled at 4 different workloads for 5 min each. For visit 3, subjects completed 60 min of cycling exercise at a previously determined workload eliciting a Hprod of 7 W/kg in a thermoneutral laboratory environment (22°C, 39% rh). Minute ventilation (VE) and inspired and expired temperature and humidity were measured. RHL was calculated at baseline (BL) and during min 0-10, 25-30, and 55-60 of exercise. Tc was measured using a telemetric pill ingested ~10 hrs prior to testing. RESULTS: There were no differences in RHL (Cres, Eres, or Tres) between PFO+ and PFO- men at rest or during exercise (p>0.05). Using a two-way ANOVA (Tres RHL X Exercise), there was a main effect of exercise on RHL (p<0.01), with RHL being greater at all 3 time points compared to rest and at min 55-60 vs min 0-10 (p<0.01). Tc was significantly higher in PFO- vs PFO+ men at rest and during exercise (PFO- 37.13 ± 0.18 °C, PFO+ 36.89 ± 0.19 °C at rest vs. PFO- 37.62 ± 0.16°C, PFO+ 37.44 ± 0.16°C during exercise; p<0.05). CONCLUSION: As expected, RHL increased from rest to exercise due to increases in VE and metabolic heat production. However, since there was no difference in RHL between PFO+ and PFO- men in this study, RHL is not likely the mechanism to explain the differences in Tc seen between PFO+ and PFO- men. Why the PFO- subjects had a higher core temperature in this study remains unknown.
Description
27 pages
Keywords
Patent Foramen Ovale, respiratory heat loss, men, exercise, rest, RHL, PFO