Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 150; Flight Crew Total 8400; Flight Crew Type 2000
Physiological - Other
Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Illness / Injury
Air Traffic Control Provided Assistance; Flight Crew Took Evasive Action; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Became Reoriented
Aircraft; Human Factors
[Enroute] everything was normal; we had portable oxygen system which was engaged. I climbed to 17;000 feet and then climbed to 25;000 feet. I observed the passenger leaning forward as the oxygen line was not long enough to reach the rear seat. I moved the oxygen bottle from between the pilot and co-pilot seat. I assume my oxygen line kinked and the passenger's was working well. I subsequently lost consciousness and the passenger moved to the co-pilot seat.With help from Air Traffic Controllers the plane was brought back down to a lower altitude; I recovered and I landed at the nearest airport where emergency personnel checked both our vitals and oxygen and all was normal.
C210 pilot reported losing consciousness at FL250 after his oxygen hose became kinked.