Pilot using cannula for oxygen at high altitude passes out.

Attributes
ACN	286480
Time
Date	199410
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : fat
State Reference	CA
Altitude	msl bound lower : 23000 msl bound upper : 23000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : lax
Operator	general aviation : personal
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : private
Experience	flight time last 90 days : 80 flight time total : 1175 flight time type : 425
ASRS Report	286480
Person 2
Affiliation	Other
Function	observation : passenger
Qualification	other other : other
Events
Anomaly	other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : became reoriented flight crew : exited adverse environment
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

On a flight from oregon to southern california at FL230, I was using a cannula connected to my oxygen system (built- in_, and level, on autoplt. My passenger was a pilot but one with whom I regularly fly and who is fairly knowledgeable) agreed to monitor the plane and instruments so that I could take a quick nap. During a 30 min sleep, I apparently breathed with my mouth open (as I do) and got insufficient oxygen through the cannula. Upon awakening, I immediately passed out and remained so for several mins. Upon awakening, I was unable to see, to focus my eyes, or to raise my hands. With effort (fighting the autoplt and autoplt induced up-trim), my passenger was able to descend to a lower altitude, at which point I regained my faculties and was able to continue the flight without further incident. Moral: sleeping with cannulas while breathing through your mouth isn't a good idea at FL230. As other pilots I've talked to regularly use cannulas over 18000 ft, some education and awareness of their limitations seems useful.

Original NASA ASRS Text

Title: PLT USING CANNULA FOR OXYGEN AT HIGH ALT PASSES OUT.

Narrative: ON A FLT FROM OREGON TO SOUTHERN CALIFORNIA AT FL230, I WAS USING A CANNULA CONNECTED TO MY OXYGEN SYS (BUILT- IN_, AND LEVEL, ON AUTOPLT. MY PAX WAS A PLT BUT ONE WITH WHOM I REGULARLY FLY AND WHO IS FAIRLY KNOWLEDGEABLE) AGREED TO MONITOR THE PLANE AND INSTS SO THAT I COULD TAKE A QUICK NAP. DURING A 30 MIN SLEEP, I APPARENTLY BREATHED WITH MY MOUTH OPEN (AS I DO) AND GOT INSUFFICIENT OXYGEN THROUGH THE CANNULA. UPON AWAKENING, I IMMEDIATELY PASSED OUT AND REMAINED SO FOR SEVERAL MINS. UPON AWAKENING, I WAS UNABLE TO SEE, TO FOCUS MY EYES, OR TO RAISE MY HANDS. WITH EFFORT (FIGHTING THE AUTOPLT AND AUTOPLT INDUCED UP-TRIM), MY PAX WAS ABLE TO DSND TO A LOWER ALT, AT WHICH POINT I REGAINED MY FACULTIES AND WAS ABLE TO CONTINUE THE FLT WITHOUT FURTHER INCIDENT. MORAL: SLEEPING WITH CANNULAS WHILE BREATHING THROUGH YOUR MOUTH ISN'T A GOOD IDEA AT FL230. AS OTHER PLTS I'VE TALKED TO REGULARLY USE CANNULAS OVER 18000 FT, SOME EDUCATION AND AWARENESS OF THEIR LIMITATIONS SEEMS USEFUL.

Data retrieved from NASA's ASRS site as of July 2007 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.