Hearing is one of the last senses to be impaired or lost. Thinking is slow. Calculations are unreliable. Memory is faulty. Judgment is poor.
Reaction time is delayed.
Over-breathing due to excitement or stress. In the critical stage consciousness is lost. Death follows shortly. An immediate descent below 10,000-feet msl will provide rapid recovery from hypoxia's symptoms. Some susceptible persons will require supplemental oxygen at altitudes lower than those specified by regulation.