FORAMEN OVALE AND IMPAIRED PULMONARY GAS EXCHANGE EFFICIENCY AT REST AND DURING EXERCISE: SIZE MATTERS

T. Kelly1, K. Carey1, J. Elliot2,3, R.C. Roach4, A.T. Lovering1 1University of Oregon, Eugene, OR; 2Oregon Health Science University, Portland, OR;3ORVA Oregon Health Care System, Portland, OR; 4UC Denver Anschutz Medical Campus, Denver, CO The patent foramen ovale (PFO) is a source of right-to-left intracardiac shunt. Previous studies have not studied the association of PFO size on pulmonary gas exchange efficiency at rest and during exercise. PURPOSE: To quantify differences in pulmonary gas exchange efficiency between individuals with a large PFO and those with a small PFO and/or no PFO. METHODS: 25 subjects (7 large PFO, 5 small PFO and 13 no PFO) were recruited and screened for presence and size of PFO utilizing saline contrast echocardiography. Large PFO was defined as Grade 3, small PFO as ≤Grade 2 and no PFO as absence of saline contrast bubbles. Subjects exercised at 5 submaximal workloads (70-190 Watts). Arterial blood was taken from a radial arterial catheter pre-exercise and during the final 30 seconds of each workload and immediately analyzed for pH, PaCO2and PaO2. Alveolar PO2was calculated using the alveolar gas equation and the alveolar-to-arterial oxygen difference (gold standard measure of pulmonary gas exchange efficiency) was quantified. Comparisons were made using a 2 way ANOVA (group x time) with Bonferroni correction for pairwise comparisons, with significance set at pRESULTS: The presence of large PFO was associated with significantly decreased pulmonary gas exchange efficiency, compared to those subjects with a small PFO and no PFO with a specific pairwise difference at 160W (19.0 ± 2.8 vs 10.7 ±1.6; (mean ± SEM)). CONCLUSION: The presence of a large PFO is associated with impaired pulmonary gas exchange efficiency pre-exercise and during moderate sub-maximal workloads. Support: American Heart Association (A.T. Lovering); Department of Defense (W81XWH-11-2-0040 TATRC to R.C. Roach and W81XWH-10-2-0114 to A.T. Lovering)