There are no effective therapies for kidney injury after cardiac surgery, but there is evidence that recovery is possible if the processes of injury - i.e., impaired oxygen delivery, increased inflammatory response, and oxidative stress - are ameliorated soon after the onset of injury. Hyperbaric oxygen therapy (HBOT) - which entails the intermittent inhalation of 100% oxygen in a hyperbaric chamber at a pressure higher than one absolute atmosphere (> 760 mmHg) - has been shown to positively affect all of these processes (i.e., to improve tissue oxygenation, reduce inflammation, and reduce oxidative stress). Thus, we hypothesized that HBOT will reduce the severity of kidney injury after cardiac surgery if it is initiated soon after onset of injury. This hypothesis has not been tested in humans, but is supported by animal studies.