AltitudeOmics: pulmonary gas exchange efficiency in humans with and without a PFO following 16 days of acclimatization to 5,260 m (885.2)

A PFO is a source of intracardiac shunt causing impaired pulmonary gas exchange efficiency, defined by an increased alveolar‐to‐arterial PO 2 difference (AaDO 2 ). Prior studies investigating human acclimatization to high altitude (HA) have not investigated differences between subjects with a patent foramen ovale (PFO+) and those without (PFO−), yet prevalence of PFO in the general population is ~40%. Twenty‐one (11 PFO+) healthy lowlanders were studied at rest and at 70, 100, 130, and 160W of cycle ergometer exercise at sea level (SL), in acute hypoxia at 5,260 m (ALT1), and after 16 days of acclimatization to 5,260 m (ALT16). Exercise data were compared at the highest iso‐workload, within an individual, achieved at SL, ALT1 and ALT16. During exercise at SL, PFO+ subjects demonstrated a wider AaDO 2 compared to PFO− subjects, however on ALT1 the AaDO 2 was not different between PFO− and PFO+ subjects. At ALT16, unlike PFO− subjects, AaDO 2 in PFO+ subjects was not different from ALT1. Surprisingly, at ALT16 the PFO+ group did not demonstrate an increase in resting minute ventilation and consequently, did not increase either alveolar PO 2 or arterial PO 2 relative to ALT1. Taken together, our data suggest that 1) intracardiac shunt in PFO+ subjects results in significantly worse pulmonary gas exchange efficiency after acclimatization to HA and 2) these subjects demonstrate physiological changes consistent with a reduced ability to acclimatize to HA. Grant Funding Source : Supported by: Department of Defense #W81XWH‐11‐2‐0040