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What I Learned in Pilot Training: Hypoxia

I realized I have not been holding up my end of the bargain when it comes to all of the things I am learning at pilot training, so I am going to do my best to start to remedy that.

For the first two weeks of training the vast majority of what we talked about was the physiological aspects of flying airplanes.  I talked about some of this in my last post, but there is one area that I feel warrants its own separate discussion, and that is hypoxia.

A quick Google search tells us that hypoxia is a “deficiency in the amount of oxygen reaching the tissues”.  This definition is pretty general, but that is because the effects of hypoxia can vary dramatically.  That is one of the scary things about hypoxia is that it is different for everyone, so there is no way to give anyone a surefire way to know it is happening.

Maybe even scarier is that some of the potential symptoms can be exact opposite.  Some people will feel euphoric, or extra happy.  Other people will feel sick and miserable.  Some of the other symptoms are tingling in the extremities, headache, feeling warm, decreased visual acuity, cyanosis (blueness in the lips), and loss of mental capacity.

The last one may be the biggest threat to pilots, but if you are struggling to think clearly, how likely are you to notice it?  Your brain isn’t working well, but somehow it is supposed to realize that it isn’t working well?

As part of our training, we go into an altitude chamber to experience the effects of hypoxia, and determine what our own individual symptoms are.  It is invaluable training and helps you to recognize how you respond so that should it ever happen in flight, you are more likely to notice it.  To add to the challenges of hypoxia, your symptoms can change over time.

When I did the altitude chamber in navigator school, my only symptom was a very slight headache across my forehead that took forever to appear.  When I did it this time it was tingling in my fingers and feeling warm.  You may notice that most of these symptoms are things that could happen for dozens of different reasons.  Lots of people get headaches when they fly because they are dehydrated or a little sick, or because they had too much fun at the bar the night before.

Which brings me to some of the different reasons that you can experience hypoxia.  There are four general types of hypoxia: histotoxic hypoxia, stagnant hypoxia, hypemic hypoxia, and hypoxic hypoxia

Histotoxic hypoxia is the type that would be created by having too much fun at the bar the night before.  Substances like alcohols, narcotics, and other drugs impact the cell’s ability to accept oxygen and even though there may be enough in the air, it can’t get into the cells to do work.

Stagnant hypoxia happens when the blood is not flowing to the tissues properly.  In the military world this is usually driven by pulling G’s which causes the blood to pool in the lower extremities and thus not flow to your upper body.  It can also happen when you get cold and your circulation decreases.

Hypemic hypoxia is similar to histotoxic, but instead of the cells not accepting oxygen, it relates to the blood’s inability to carry oxygen.  In aviation this is most often caused by the inhalation of carbon monoxide either from a bad heater, or even just the exhaust on the ground before you get in and takeoff.

Hypoxic hypoxia is when the air simply does not have enough oxygen for your to breathe, which happens at higher altitudes.  Clearly an issue for flying an airplane.  It is also the most common type of hypoxia experienced in aviation.

We can all agree that hypoxia is a bad thing as it prevents us from thinking clearly and from using our body to safely operate an airplane.  So what can we do to prevent it, or recognize it when it does happen?

First, prevention because it is ALWAYS better to prevent a bad situation that it is to deal with it after it arises.  Being physically prepared to fly is the simplest way to prevent hypoxia, and a host of other issues.  That means that if you have not gotten enough rest, or you have been feeling sick, or you are hung over, or drunk, then you should not be flying.  We all want to fly as much as possible, but you have to know your limits and never cross them.  Even in the military we regularly talk about how there are almost no flights that cannot wait until another day if the crew is not physically fit to fly.

Another part of prevention is ensuring that you have the proper equipment for the flying you will doing.  If your flight is going to be mostly around sea level hypoxic hypoxia is not very likely, but if you have a broken exhaust system, or a cabin heat system that is not working properly, you put yourself at very real risk of hypemic hopxia, and that is every bit as dangerous.  Hypoxia is not only a matter of flying at high altitude!

Generally speaking we talk about oxygen deficiency starting at around 10,000 feet MSL.  So if you are planning to fly anywhere near that altitude for very long you need to have the right equipment.  That could be a pressurized cockpit, or it could be supplemental oxygen.  If you will be flying at night, some people push that altitude as low as 5,000 feet MSL.  Once again, everyone is different, and has different tolerances.  If in doubt bring along the extra oxygen because it may save your life.

I realize that going to an oxygen chamber is not realistic for most people, nor is it really necessary for someone cruising around in a 172, but if you get the opportunity I would highly recommend it.  That being said, there is still plenty of education and experience you can get to learn more about the effects of hypoxia and how it can affect you.

My only experience with hypoxia, other than in the controlled environment of an altitude chamber, was actually on a hiking trip.

I was climbing Mt. Fuji in Japan, which only goes up to about 12,300 feet, not that much above 10,000.  As we got to the summit it was rainy and cold and I was miserable and I had a headache.  But, I didn’t even realize it until we were on our way back down and I started to feel better.  Sure I recognized that I was tired, but it wasn’t until I headed lower and started to lose my symptoms that I realized I had even had symptoms.

The odds of this happening in aviation are not very high, at least if it has become a critical issue.  If the symptoms are minor then descending may be enough to clear your head and fix your symptoms, but descending may not always be an option, and if it has to do with poor equipment, it is not likely that the equipment will just fix itself.

So how do you recognize that you are having issues?  The key to this is not waiting for extra signs.  At the first indication that you may be hypoxic you need to take action.  Some people can go hours with symptoms before it becomes life threatening, but for others the symptoms may come on and only minutes later the person will be incapacitated.  So if you even think there is a small chance you might be hypoxic, try to fix it immediately.

If you are fortunate enough to be flying with someone else, ask them how they are feeling, or if they see anything different with you. Sometimes just bringing it up will key the whole crew off that something is not right and you may save everyone.  Maybe it is just you having an issue though, and they can help you remedy the situation and get back to normal.  The point is to not keep it a secret if you don’t feel right.

Many people do most of their flying alone so what can they do?  In many cases, you can still tell someone, whether that be ATC or anyone else that may be on frequency with you.  Again, just mentioning that something doesn’t feel right can help key off your mind that something isn’t right and can help you down the path to fixing it.

If there is legitimately no one around then just say it out loud to no one.  The brain is pretty amazing and just vocalizing it may be enough.  Most importantly, if you are by yourself, don’t hesitate to take some action if you feel even the slightest possibility that something isn’t right because you have no idea how far you are from just passing out.

This ended up being way longer than I expected, but I would argue that I didn’t even scratch the surface on the topic, or at least on aerospace physiology.  There are people whose entire career is in that field.

Hopefully what I have done is given you some things to think about when you fly, and encouraged you to spend some extra time thinking about how your body is performing when you fly.  We spend a lot of time checking on the plane, and our equipment but most of us don’t take enough time to check on our physical ability to fly.

It doesn’t have to be a huge drawn out process, but even taking the time to stop before you step to the plane and just ask yourself how you are feeling may be what saves your life.  I would also encourage you to spend some time learning more about aerospace physiology.  That could be through articles, or YouTube, or seminars, or other classes.  No matter where it comes from, understanding how our bodies work when they are in the unnatural state of flying will only make you a better aviator.

October 12, 2019 I Written By

I'm Dave and I am a proud Avgeek. It goes way beyond liking airplanes. It is a passion that cannot be subdued.

My First Week at Air Force Pilot Training

It’s been almost a month since I last posted, and I can’t believe how fast that month has gone.  I feel like it has been much longer with everything I have done since then.

It was kind of nice to have a little bit of free time with my family for a couple of weeks after we got here, though free time is probably the wrong word.  It was nice to not have work requirements because I was able to help my wife get the house unpacked, take the kids to dance and swim lessons, and enjoy a couple of lunches with my Queenie before my life revolves around flying for the next year.

It makes me laugh a little as a type that because many people would probably say my life has always revolved around flying, but it had increasingly become more about desk work before I left.  It is super nice to just be learning about flying again, though I know that will change again when I get home, and that’s okay.

So what is the first week of pilot training like?

In a word, fast paced.  (okay, that is two words)

The first day was just briefings to get us ready for the year ahead and what the policies and procedures of the unit are.  Then starting the next day we were right into full days of academics.  With the pilot shortage they are trying to get through as many people as they possibly can.  That has led to them shortening the course by a few weeks by deleting some of the topics they deemed non-essential.  I won’t complain about getting done here sooner and getting on to C-130 training.

In the first week we have been mostly focusing on aerospace physiology, which is probably one of the least studied topics that has immense impact on effective flying, if that makes sense.  We covered topics ranging from hypoxia to G-tolerance to egressing from the aircraft.  While none of the information was new to me with my background, it was a good reminder of the importance of these topics.  It was also eye-opening to some of the guys that don’t have a background in aviation.

If we needed a reminder that this is not a take your time kind of course, our first test was a week to the day after we started and covered the full range of aerospace physiology topics.  I was happy to have done well and crossed the first hurdle in training.  I was confident about the whole thing because, as I said, none of the information was really new to me, but there is still always that little bit of fear that I won’t give something the time it deserves and I will blow it.

No time for a break though as after the test we were right back into class and CAI’s.  It is worth explaining the different ways in which we get instruction in formal courses like this.  There are basically three different methods of training: Instructor Based Training, hands-on training, and Computer Based Training.  My entire career the computer based training has been referred to as CBTs, but here it is referred to as CAI’s because why leave something alone when you can change the name for no reason.

My favorite training, like most people, is the hands-on training, but they actually have a pretty good system set up here.  Generally speaking, you spend some time learning about new topics on the computer, then you have a class with an instructor to clarify and expand on the topic, then you get into some sort of simulator, or part task trainer, or eventually the actual aircraft, to bring the whole thing together.

Now that we are mostly done with aerospace physiology, we actually have to do the altitude chamber on Monday, we have started to get into the aircraft systems of the T-6 which has been super interesting.  While we did utilize the T-6 in Nav school, that was 8 years ago, and we are going a lot more in-depth than we did back then because now I will be in control of the plane and not just sitting in the back seat.

If that sounds like quite a bit for a first week, it is, but the pace only quickens from here.  Monday will mostly be taken up by the altitude chamber, then Tuesday we have our first sims, and Wednesday is our next test.  From there it just keeps going, and I am loving every minute of it.  I’m not worried about scheduling people for stuff, or tracking training, or writing memos, or going to meetings, I am completely focused on learning to fly, and it is awesome.

It really hit me this week just how blessed I am to be here.  I am 37 years old, when the age limit was 30 when I was selected.  I started this journey to become a pilot 16 years ago when I enlisted, and now I am here.  Don’t let small hiccups or speed bumps get in the way of you getting where you want to be.

To be clear, there are some things that there is nothing you can do about, like being blind or something of that nature.  But, if something like money, or age, or scores, or even just doubt are holding you back, then don’t give up.  You can find a way, and you can get there, just don’t give up, and ask for help.

There are doubters and haters out there, but there are also a ton of people out there that would love to help and return the favor for the help they received.  So reach out to anyone and everyone and figure out how to make it happen.

If you have any questions about the stuff we are learning or how you can get here too, let me know and I would be happy to help you.

September 14, 2019 I Written By

I'm Dave and I am a proud Avgeek. It goes way beyond liking airplanes. It is a passion that cannot be subdued.