Narrative:

Oxygen regulator failure. Delayed in executing an emergency descent. Center kept us at altitude longer than we should have. In retrospect we should have declared an emergency to get a lower altitude. Controller didn't understand the severity of the situation because we didn't go into much details.

Google
 

Original NASA ASRS Text

Title: A C182 PILOT REPORTED HIS OXYGEN REGULATOR FAILED AT 16000 FT AND HE WAS SLOW TO DESCEND TO A SAFE ALT.

Narrative: OXYGEN REGULATOR FAILURE. DELAYED IN EXECUTING AN EMER DSCNT. CTR KEPT US AT ALT LONGER THAN WE SHOULD HAVE. IN RETROSPECT WE SHOULD HAVE DECLARED AN EMER TO GET A LOWER ALT. CTLR DIDN'T UNDERSTAND THE SEVERITY OF THE SITUATION BECAUSE WE DIDN'T GO INTO MUCH DETAILS.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.