Researchers have found that hypoxia can be detected prior to the appearance of physical symptoms.

Jan Stepanek, M.D., the Aerospace Medicine Program Director and Co-Director of the Aerospace Medicine and Vestibular Research Laboratory, said that this study opens the door for objective assessments of hypoxia and additional safeguards for military and commercials pilots and others working in high altitudes.

Hypoxia is a lower than normal level of oxygen in your blood. To function properly, your body needs a certain level of oxygen circulating in the blood to cells and tissues.

When this level of oxygen falls below a certain amount, hypoxia can cause a variety of symptoms including shortness of breath, impaired speech, slowed reaction time and passing out.

The Mayo Clinic study team used the King-Devick neurocognitive performance test , commonly used to identify cognitive changes related to sports-related concussions, and to assess cognitive function under conditions of low oxygen-simulating altitude.

The King-Devick test assesses the time in viewing, identifying and reading aloud a series of numbers on three consecutive test cards. Based on test times of 25 participants, the study concluded that the King-Devick test is an effective tool to detect "impairment of cognitive performance at a presymptomatic stage of hypoxia."

The findings have been published in journal Aviation, Space, and Environmental Medicine.