Xenon Inhalation Therapy for Major Depressive Disorder and Bipolar Disorder

The investigators have chosen to use as a maximum concentration about half the general anesthetic partial pressure of xenon (35%=70%/2) to achieve a dose that is sub-anesthetic. This concentration of xenon is very close to that at which subjects emerging from xenon anesthesia first respond to verbal commands, commonly referred to as MAC awake.

nitrogen-oxygen (35:65 ratio by volume) added to treatment as usual