An oxygen concentration less than _% will cause convulsions, cessation of breathing, and cardiac arrest.

An oxygen concentration less than _% will cause convulsions, cessation of breathing, and cardiac arrest.

• A. 6%
• B. 4%
• C. 8%
• D. 2%

Answer: (A)

Oxygen levels that low deprive the body's tissues of the oxygen they need, with the brain and heart being especially sensitive. When inspired O2 falls to about 6%, brain cells can no longer meet their metabolic demands, leading to loss of consciousness and even convulsions. If breathing continues in such an environment, breathing can stop (apnea) and the heart can fail from the lack of oxygen, causing cardiac arrest. Normal air is about 21% O2, so these severe hypoxic effects occur at single-digit percentages, with 6% being the threshold commonly cited for this dangerous sequence.

Oxygen levels that low deprive the body's tissues of the oxygen they need, with the brain and heart being especially sensitive. When inspired O2 falls to about 6%, brain cells can no longer meet their metabolic demands, leading to loss of consciousness and even convulsions. If breathing continues in such an environment, breathing can stop (apnea) and the heart can fail from the lack of oxygen, causing cardiac arrest. Normal air is about 21% O2, so these severe hypoxic effects occur at single-digit percentages, with 6% being the threshold commonly cited for this dangerous sequence.