AltitudeOmics: effect of reduced barometric pressure on detection of intrapulmonary shunt, pulmonary gas exchange efficiency, and total pulmonary resistance

Blood flow through intrapulmonary arteriovenous anastomoses (QIPAVA) occurs in healthy humans at rest and during exercise when breathing hypoxic gas mixtures at sea level and may be a source of right-to-left shunt. However, at high altitude QIPAVA is reduced compared to sea level as detected using transthoracic saline contrast echocardiography (TTSCE). It remains unknown whether the reduction in QIPAVA (i.e., lower bubble scores) at high altitude is due to a reduction in bubble stability resulting from the lower barometric pressure (PB), or represents an actual reduction in QIPAVA. To this end, QIPAVA, pulmonary artery systolic pressure (PASP), cardiac output (QT) and the alveolar-to-arterial oxygen difference (AaDO2) were assessed at rest and during exercise (70-190W) in the field (5,260m) and in the lab (1,668m) in 4 conditions; normobaric normoxia (NN; PIO2=121 mmHg, PB=625 mmHg, n=8), normobaric hypoxia (NH; PIO2=76 mmHg, PB=625 mmHg, n=7), hypobaric normoxia (HN; PIO2=121 mmHg, PB=410 mmHg, n=8), and...