The Effect of a Patent Forman Ovale on Thermoregulatory and Ventilatory Responses During Passive Heating and Cooling
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Date
2016-06
Authors
Hay, Madeline
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
A patent foramen ovale (PFO) is an intracardiac shunt present in ~1/3 of the general population that allows varying degrees of blood flow to bypass pulmonary circulation and respiratory cooling. The aim of this research was to determine how the presence of a PFO affected thermoregulatory and ventilatory responses to passive heating and cooling. During passive heating, ventilation increases in order to augment heat dissipation from the respiratory system. Because individuals with a PFO (PFO+) have a
higher resting core temperature (Tcore), it was hypothesized that PFO+ subjects would
increase their ventilation at a higher Tcore than subjects without a PFO (PFO-) during
passive heating. Additionally, shivering is implemented in order to generate heat during
passive cooling. Because PFO+ individuals have a higher resting Tcore, it was
hypothesized that the PFO+ group would shiver at a higher Tcore, To test these
hypotheses, 22 well-matched males (11 PFO+ and 11 PFO-) completed a passive
heating and a passive cooling trial. In the passive heating environment, individuals
were immersed in a 40.5±0.3°C water bath until 1) 30 minutes had elapsed, 2) their esophageal temperature (Tesoph) reached 39.5°C, 3) they became lightheaded, or 4) they requested to get out. In the passive cooling environment, individuals were immersed in a 19.7±0.6°C water bath until 1) 60 minutes elapsed, 2) their Tesoph dropped to 35.5°C, 3) sustained shivering occurred, or 4) they requested to get out. In both trials, PFO+ had a higher Tesoph (p < 0.05). At the end of hot water immersion, PFO+ subjects had significantly lower minute ventilation than PFO- subjects (p < 0.05). Additionally,
PFO+ subjects shivered at a significantly higher Tesoph than the PFO- subjects during
the cold water immersion (p < 0.05). The results suggest that individuals with a PFO
have a significantly higher Tcore, and that this greater temperature is defended in both
hot and cold environments. These results may help us further understand how the
presence of a PFO affects an individual’s response to environmental conditions, as well
as why some people may be more prone to certain thermal illnesses.
Description
41 pages. A thesis presented to the Department of Human Physiology and the Clark Honors College of the University of Oregon in partial fulfillment of the requirements for degree of Bachelor of Science, Spring 2016.
Keywords
Patent Foramen Ovale, Human physiology, Biology, Temperature, PFO, Thermoregulation, Ventilation, Passive heating, Passive cooling