NTSB Identification: ANC02IA093.
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Nonscheduled 14 CFR
Incident occurred Tuesday, June 18, 2002 in TALKEETNA, AK
Probable Cause Approval Date: 09/30/2003
Aircraft: Piper PA-31-350, registration: N828KT
Injuries: 1 Serious,8 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

A passenger with a history of coronary artery disease, and coronary surgery, became unconscious in a non-pressurized twin-engine airplane during a sightseeing flight at 21,000 feet. All passengers on the flight were utilizing supplemental oxygen from the airplane's oxygen system. The passenger was supported in an upright, seated position as the flight returned to the departure airport where she was met by emergency medical personnel and transported by ambulance, lying down on a stretcher. The passenger regained consciousness en route to a hospital for initial treatment where diagnostic studies were consistent with heart attack and congestive heart failure. Although her initial diagnosis included possible high altitude pulmonary and cerebral edema, this is unlikely since the flight was less than 1 hour and these symptoms usually occur only after a day or more exposure to high altitude. The passenger's condition was most likely related to her previous history of heart disease, exacerbated by exposure to decreased oxygen supply, and continuous vertical position for many minutes following her loss of consciousness. The passenger was subsequently released for in-home rehabilitation two months later with a diagnosis of an anoxic brain injury. According to the pilot's operating handbook, the FAA approved passenger oxygen mask for the incident airplane is a partial rebreather mask equipped with a reservoir bag at a flow rate of 1.5 or 2.0 liters per minute, however, on the incident flight, the passengers were using a disposable, hospital type oxygen mask without a reservoir bag, at a flow rate of 1.5 liters per minute. FAA oxygen system certification standards, at 21,000 feet, require a minimum flow rate of about 1.8 liters per minute, and the recommended upper altitude limit for use of an oxygen mask without a reservoir bag is 15,000 feet. Following the incident, the operator changed the passenger oxygen masks to an FAA approved mask with a reservoir bag, at a flow rate of 3.0 liters per minute.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

The passenger's incapacitation during a high altitude flight due to a loss of consciousness as the result of a pre-existing cardiovascular condition. A contributing factor in the incident was the operator's improper use of disposable oxygen masks without a reservoir bag above the recommended upper altitude limit for use of this type mask.

Full narrative available

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