SR22
Flight Crew Multiengine; Flight Crew Commercial; Flight Crew Instrument
Flight Crew Last 90 Days 20; Flight Crew Total 2000; Flight Crew Type 900
Situational Awareness; Physiological - Other
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural FAR
Flight Crew Took Evasive Action
Aircraft; Human Factors
My wife and I were cruising at 16;000 feet; using O2 with cannulas.  Because of an aircraft crash [nearby]; the Controller directed us to enter holding; maintaining 16;000 feet.  Entering holding was routine; I started calculating how long I could remain in holding before diverting (approximately one hour); and I selected [a] potential diversion field.  My wife noticed that our O2 was no longer flowing from the portable bottle.  I did some troubleshooting and discovered that we were out of oxygen.  I notified the Controller that we were out of oxygen; we needed an immediate descent to below 14;000; and we needed to divert.  The Controller authorized a descent to 15;000 feet and cleared me direct to [a diversion airport].  I was having difficulty loading any approach into my avionics and even finding the approach plate.  My flight path was erratic; but the Controller did not mention anything due to his workload.  Looking back on my performance; I was clearly hypoxic.  I again mentioned that I needed to get below 14;000 as soon as possible.  I wanted to maintain my then current heading; and turn right to intercept the localizer; but that was not the published approach.  The Controller gave me vectors that mimicked the approach and I succeeded in intercepting the ILS and eventually landed.Pilots who suspect that they might be hypoxic should declare an emergency immediately; but; hypoxic pilots often do not recognize that they are hypoxic.  When a pilot flies erratically; is not abiding by published procedures; or is not communicating well; the Controller should declare the emergency and get the aircraft below 14;000 feet or on the ground ASAP.
SR-22 pilot reported he became hypoxic when his oxygen bottle emptied at 16;000 feet.