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

Abstract

A PFO is a source of intracardiac shunt causing impaired pulmonary gas exchange efficiency, defined by an increased alveolar‐to‐arterial PO2 difference (AaDO2). 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 AaDO2 compared to PFO− subjects, however on ALT1 the AaDO2 was not different between PFO− and PFO+ subjects. At ALT16, unlike PFO− subjects, AaDO2 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 PO2 or arterial PO2 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