This report describes a patient with mucormycosis treated with hyperba
ric oxygen therapy (HBO2). Arterial O-2 tension (PaO2) during HBO2 was
considerably lower (346 mm Hg) than expected (1,500 mm Hg) due to an
inadvertent right main-stem intubation, which was not otherwise clinic
ally evident. This case illustrates the influence of a large right-to-
left shunt (Qs/Qt) on O-2 loading during HBO2. We raise the question i
f routine hyperbaric treatment protocols are adequate to raise PaO2 in
patients with large Qs/Qts.