Tag: Andrew Lovering

The Effect of a Patent Foramen Ovale on Thermoregulatory and Ventilatory Responses During Passive Heating and Cooling

Presenter: Madeline Hay

Faculty Mentor: Andrew Lovering, Louise Bishop

Presentation Type: Poster 68

Primary Research Area: Science

Major: Human Physiology

A patent foramen ovale (PFO) is an intracardiac shunt present in ~1/3 of the population that allows blood flow to bypass pulmonary circulation which may reduce respiratory cooling. During passive heating, ventilation increases to dissipate heat from the lungs. Because individuals with a PFO (PFO+) have a higher core temperature (Tcore), it was hypothesized that PFO+ subjects would increase ventilation at a higher Tcore than subjects without a PFO (PFO-) during passive heating and would shiver at a higher Tcore during passive cooling. 22 males (11 PFO+, 11 PFO-) completed a passive heating and passive cooling trial. For passive heating, individuals were immersed in a 40°C water bath until 1) 30 minutes elapsed, 2) Tcore reached 39.5°C, 3) they felt lightheaded or 4) they requested to exit. For passive cooling, individuals were immersed in a 20°C water bath until 1) 60 minutes elapsed, 2) Tcore reached 35.5°C, 3) sustained shivering occurred or 4) they requested to exit. In both trials, PFO+ had a higher Tcore. During passive heating, PFO+ had a lower ventilation than PFO-. Additionally, PFO+ shivered at a higher Tcore than the PFO-subjects during passive cooling. The results suggest that PFO+ have a higher Tcore and that this greater temperature is defended in both hot and cold environments. A PFO may be beneficial by preventing hypothermia but detrimental by facilitating heat stroke.

Investigating the Relationship between Acute Mountain Sickness, Patent Foramen Ovale, and Systemic Inflammation

Presenter(s): Karina Shah—Human Physiology

Faculty Mentor(s): Kaitlyn DiMarco, Andrew Lovering

Session: Prerecorded Poster Presentation

Acute mountain sickness (AMS) occurs when individuals rapidly ascend to high altitude, but its exact cause is unknown . A patent foramen ovale (PFO) is a hole in the heart present in one-third of the population . PFO+ subjects have greater AMS incidence, but the reasons are unknown . AMS is associated with systemic inflammation as determined by elevated cytokines and data from our lab suggests that PFO+ subjects have greater systemic inflammation . Thus, we hypothesized that the association between AMS and PFO is explained by increased inflammation . To test this, 17 PFO+ subjects (9 women) and 17 PFO- subjects (9 women) were exposed to 10 hours of hypoxia simulating 15600 feet and AMS was assessed using the Lake Louise Questionnaire . Blood samples taken before and at 10 hours of hypoxia were assayed for 13 inflammatory mediators . We found that 83% of PFO+ subjects but only 61% of PFO- subjects got AMS . AMS- subjects had significantly higher levels of IL-12p70 at 10 hours than AMS+ subjects . All other cytokines had significant time effects, and the greatest increases were in AMS- subjects . Compared to PFO- subjects, PFO+ subjects had significantly higher IL-1Î2, interferon (IFN)-α2, IL-8, IL-10, and MCP-1 levels before and at 10 hours . PFO+ subjects had the greatest increases in IFN-α2, MCP-1, and IL-10 and PFO- subjects had the greatest increases in IL-1Î2 and IL-6 . These data suggest inflammation levels differ with PFO and AMS, but with separate patterns . Therefore, systemic inflammation in AMS and PFO may be more complex than previously thought .

Cardiopulmonary Differences in Apnea Divers Breathing Isocapnic Normobaric Hypoxia

Presenter(s): Mohini Bryant-Ekstrand—Human Physiology

Faculty Mentor(s): Andrew Lovering, Tyler Kelly

Session: Prerecorded Poster Presentation

Hypoxia (low oxygen), induces a reversible form of pulmonary hypertension which can be studied to elucidate the etiology of pulmonary hypertension and right heart dysfunction . Breath hold divers (BHD) routinely place themselves into extremely hypoxemic (low blood oxygen) conditions and therefore may repeatedly expose themselves to acute bouts of pulmonary hypertension and increased right heart work . A patent foramen ovale is a tunnel between the top chambers (atria) of the heart present in 35% of the populations that may exacerbate hypoxemia thereby worsening pulmonary hypertension . The purpose of this study was to 1) determine if pulmonary arterial pressure and right heart dysfunction in hypoxia was greater in BHD compared to controls, 2) determine if the presence of a PFO contributed to the responses measured and 3) determine the role of a pulmonary vasodilator in ameliorating the increased pulmonary pressure in response to hypoxia . Subjects (n=26, 13 BHD, 13 Control) completed two 30-minute hypoxic breathing challenges, after receiving either 50mg sildenafil or placebo, with a 48-hour minimum washout period between visits . Saline contrast echocardiography was used to detect PFO . Pulmonary pressure and right heart function measures were made using Doppler ultrasound . Compared to placebo, sildenafil produced vasodilation before hypoxia in BHD and after 30 minutes of hypoxia in controls . PFO had no effect . Our preliminary data suggests elite breath hold divers may have a chronic pulmonary vasoconstriction in room air that is prevented with administration of sildenafil, and these findings are independent of having a PFO .