By Margaret Anderson<\/p>\n
What\u2019s a traveler\u2019s worst nightmare? Is it a sudden drop in cabin pressure with oxygen masks falling like dangling jellyfish above the passengers\u2019 heads, or is it no masks at all?<\/p>\n
That\u2019s just what happened Tuesday morning when a United flight made an emergency landing at O\u2019Hare International Airport after a pressurization issue sickened passengers.<\/p>\n
The plane\u2019s oxygen masks did not deploy, said Karen May, a public relations manager for United Airlines.<\/p>\n
Will Knight, a spokesman for the Chicago Fire Department, said 176 people were checked after complaining of ear pain and nausea. No passengers or crew were hospitalized.<\/p>\n
United 1218 departed O\u2019Hare for Denver at 8:40 a.m. with 174 passengers and seven crew members on board. The plane, a Boeing 737-900, was forced to return to Chicago an hour later after passengers began to feel sick, May said.<\/p>\n
Paramedics boarded the airplane within five minutes of landing and no passengers or crew were taken to the hospital, Knight said.<\/p>\n
Air pressure inside an airplane cabin is controlled by mixing outside air with recirculated air from the cabin, a system that also regulates airflow and temperature, according to Boeing<\/a>.<\/p>\n Like soda bubbles appearing when a bottle is opened, when airplane cabin pressure drops, nitrogen, normally dissolved in bodily fluids, turns back into a gas. The phenomenon can cause ear pain, dizziness and what is commonly referred to as \u201cthe bends,\u201d according to the Federal Aviation Administration<\/a>.<\/p>\n According to May, the United flight left again for Denver a few hours late after paramedics checked passengers’ health and United Airlines maintenance inspected the aircraft.<\/p>\n