American Medical Association
Guidelines on Oxygen Equipment in CPR...

"...supplemental oxygen should be used as soon as it is possible..."
"...oxygen should not be withheld for fear of suppressing respiration..."
"The highest possible oxygen concentration (preferably 100%) should be   
   administered as soon as possible to all patients with cardiac or pulmonary arrest
   or other patients with suspected hypoxemia regardless of cause."
"Masks equipped with one-way valve...are recommended for mouth to mask
   ventilation."