* Veteran’s Corner: Hypoxia in a Huey

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By Sunny Shin

Most in-air emergencies grab your attention immediately. When your engine quits, you have no doubt what is happening, but when your brain starts to shut down, you may not even notice. Such is the danger of hypoxia.

Hypoxia is a condition in which the body is deprived of adequate oxygen supply at the tissue level. Typically hypoxic conditions occur at cabin pressure altitudes of 12,500 feet or higher for 30 minutes or more. Flights above fifteen thousand feet require supplemental oxygen for each occupant of the aircraft. Federal Aviation Regulations Part 91.211 spells out the rules in great detail.

Hypoxia is scary because it can happen anytime while flying and the pilot may not even know they have it. It causes all sorts of problems, such as high altitude pulmonary edema, high altitude cerebral edema, unconsciousness, and even death. All of which are obviously bad while flying an aircraft.

One of the most important parts of the US Army flight school was hypoxia training. Since every person experiences hypoxia differently, the Army exposes it to us in a controlled situation so that we can recognize these symptoms while flying and immediately do something about it.

I flew a UH-1 Huey, the helicopter you see in all the Vietnam war movies. It is an iconic helicopter and has a unique look. While flying, it makes a sound like no other helicopter.
Our helicopters are not pressurized like the commercial jets people fly in. We typically fly slow and low but there are times we fly at higher altitudes where we could experience hypoxia.
After a week of receiving classroom lectures of flying in various conditions and their physiological effects, the day finally comes to actually experience them. This is the day to certify that we have received a high altitude experience, in order to recognize possible hypoxia symptoms and how to avoid them. So, our class headed out to a high altitude chamber.

Inside, the chamber is similar to a classroom, two rows, left and right with 10 seats in a row. All cadres are in oxygen masks walking up and down the aisle. There were round window ports to each seat. Radio communications were strictly followed by the chamber operator and cadres. Finally, we get clearance to go up in altitude.

They are announcing the altitude we are simulating through the chamber speaker. All cadres are walking up and down the aisle asking for our name, SS number, date of birth, etc..
I remember I was giving my social security number but that was it. The next thing I remember is hearing our altitude through the speaker but it was much lower than I heard last. We were descending.

The cadre asked us if we remembered anything and if we wanted to see the video of ourselves.

None of us could believe what we were seeing. As we got close to hypoxia, we all acted so differently. One wanted to fight, others were just crying, some were just zombies, another was singing. I was trying to sing “My Girl” but I couldn’t get the lyrics right. One thing was for sure, no one was able to answer any of the cadre’s questions correctly.


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