This study will look at the changes taking place in the blood levels of key markers of oxidative stress. Oxidative stress is the biological equivalent of rust on a car. It changes vital cell chemistry. It is known to occur at high pressure oxygen, but little is known about changes at pressures slightly greater than normal atmospheric pressure.

Hyperbaric therapy is used in a variety of medical conditions. It is being tested in this study only for safety. It is not being assessed for the ability of hyperbaric oxygen to improve the clinical condition of children with autism.

This study was felt to be important since autism appears to be associated with oxidative stress and hyperbarics was being used "off-label" for this condition without safety studies.

Blood will be drawn immediately prior to a one hour session of hyperbarics (HBT. A catheter will be inserted in to a vein and converted to a heparin lock indwelling port for the next blood draw. The child (ages 5-12 years) will then undergo 1 hour of compression at 1.3 atmospheric pressure (4 psi above room air pressure). Supplemental oxygen will be provided to the child.

A second blood draw from the catheter site will be accomplished immediately after the child comes out of the HBT chamber.

These will be sent to the laboratories for evaluation of changes in reduced glutathione and lipid peroxides.

Inclusion Criteria:

• Children diagnosed with autism ages 5-12 and undergoing hyperbarics

Exclusion Criteria:

• Seizures, acute URI, or inability to ventilate ears