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. 2015 Oct 15;593(20):4615-30.
doi: 10.1113/JP270219. Epub 2015 Aug 13.

Higher oesophageal temperature at rest and during exercise in humans with patent foramen ovale

James T Davis  1 , Chi-Yan A Ng  1 , Sierra D Hill  1 , Richard C Padgett  2 , Andrew T Lovering  1
Affiliations

Higher oesophageal temperature at rest and during exercise in humans with patent foramen ovale

James T Davis et al. J Physiol. .

Abstract

Respiratory system cooling occurs via convective and evaporative heat loss, so right-to-left shunted blood flow through a patent foramen ovale (PFO) would not be cooled. Accordingly, we hypothesized that PFO+ subjects would have a higher core temperature than PFO- subjects due, in part, to absence of respiratory system cooling of the shunted blood and that this effect would be dependent upon the estimated PFO size and inspired air temperature. Subjects were screened for the presence and size of a PFO using saline contrast echocardiography. Thirty well-matched males (15 PFO-, 8 large PFO+, 7 small PFO+) completed cycle ergometer exercise trials on three separate days. During Trial 1, subjects completed a V̇(O2max) test. For Trials 2 and 3, randomized, subjects completed four 2.5 min stages at 25, 50, 75 and 90% of the maximum workload achieved during Trial 1, breathing either ambient air (20.6 ± 1.0°C) or cold air (1.9 ± 3.5°C). PFO+ subjects had a higher oesophageal temperature (T(oesoph)) (P < 0.05) than PFO- subjects on Trial 1. During exercise breathing cold and dry air, PFO+ subjects achieved a higher T(oesoph) than PFO- subjects (P < 0.05). Subjects with a large PFO, but not those with a small PFO, had a higher T(oesoph) than PFO- subjects (P < 0.05) during Trial 1 and increased T(oesoph) breathing cold and dry air. These data suggest that the presence and size of a PFO are associated with T(oesoph) in healthy humans but this is explained only partially by absence of respiratory system cooling of shunted blood.

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Figures

Figure 1
Figure 1. Effect of PFO on HR during pre‐exercise conditions
Line indicates mean for each group. *PFO+ subjects had a higher HR than PFO– subject (P < 0.05).
Figure 2
Figure 2. Effect of PFO on V˙E during V˙O2max test
Values are means ± SEM. There was a main effect of PFO on VE˙. *Specific pairwise differences (P < 0.05).
Figure 3
Figure 3. Effect of PFO on Toesoph during V˙O2max test
Values are means ± SEM. There was a main effect of PFO on T oesoph. *Specific pairwise differences (P < 0.05).
Figure 4
Figure 4. Effect of PFO on differences in absolute change of Toesoph during relative workload tests between breathing cold and dry air and ambient air
Values are mean responses ± SEM. *There was an effect of PFO on change in Toesoph occurring during 90% of max workload (P < 0.05).
Figure 5
Figure 5. Effect of size of PFO on Toesoph during V˙O2max test
Values are means ± SEM. There was a main effect of PFO size on T oesoph. *Significant differences from PFO– (P < 0.05).
Figure 6
Figure 6. Effect of the size of PFO on differences in absolute change of Toesoph during relative workload tests between breathing ambient and cold air
Values are mean responses ± SEM. There was a main effect of PFO size on differences in T oesoph. *Significant differences from PFO– (P < 0.05).
Figure 7
Figure 7. Effect of Toesoph on V˙E / V˙O2 in PFO+ and PFO– subjects
A, relationship during the relative workload trial while breathing ambient air. B, relationship during the relative workload trial while breathing cold and dry air. PFO+ subjects did not show any change in the relationship between the two trials, while PFO– subjects showed a left shifted curve when breathing cold and dry air. Values are mean responses ± SEM.
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