What physical change would most likely occur to occupants of an unpressurized aircraft flying above 15,000 feet without supplemental oxygen?
A
Gases trapped in the body contract and prevent nitrogen from escaping the bloodstream.
B
The pressure in the middle ear becomes less than the atmospheric pressure in the cabin.
C
A blue coloration of the lips and fingernails develop along with tunnel vision.✓ Correct Answer
Explanation
Above 15,000 feet without supplemental oxygen, occupants are likely to become hypoxic, with signs such as cyanosis (blue lips and fingernails) and visual impairment like tunnel vision (PHAK Chapter 17). Trapped gases expand, not contract, with altitude, and middle-ear pressure problems occur mainly during descent.
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