Only 1 Kind of Hypoxia I Care About…

One thing all teachers have to face at one point or another is a student asking “Who cares? Why do we have to know that?” I was recently faced with that question while working with a helicopter pilot who’s sitting for his commercial ride. First some background on this pilot: he’s good. His level of confidence and skill going into his commercial ride well exceeds mine at any time during my training. He has a few things in his favor: he owns and maintains the helicopter, flies it weekly, and has over 300 hrs in it. He’s also been flying airplanes for many years, and knows more about aviation than I may ever know. Most of his flying has also been outside of flight schools. It’s awkward for somebody with as little aviation experience as myself to be “teaching” somebody at this skill level, and if anybody’s learning, it’s me.

His weak point is his book knowledge, and most of my time has been spend going over the PTS knowledge topics with him. After our last meeting, I gave him a list of topics that we needed to cover before I could feel good about signing him off, and I thought I’d heard him say he’d been studying. So I thought I’d put him to the test, hoping I could sign him off for the practical. I started with a topic we’ve all learned at the rote level: “What are the 4 types of hypoxia?”

“There are 4 types? Only one type I care about…the type where you ain’t getting enough oxygen!”

In the ensuing uncomfortable minutes, I fell into a trap that so many other teachers have. Since I couldn’t tell him outright why he should care that there are more than one type, the motivation I provided is that this is something you just have to know for the test. If he’d said “This is stupid!” or “This crap is just relevant for plank drivers” I’d have probably agreed with him as well. And what message would this have sent?

I’m going to try and atone for that now, and I’m going to try and do it with a couple of scenarios that hit the highlights. If you don’t remember, here’s the lesson plan for hypoxia. As part of a lesson on “The 4 Types of Hypoxia” these would be pretty obvious, but as part of a general lesson that included ADM scenarios, you might be able to get a student thinking beyond the rote level.

You’ve been contacted by a rancher who needs to clear some feral goats off his property. He lives in Lakeview (KLKV), and his ranch is to the east (N42 4′ 30″ W120 8′ 20″); you’ll be working mostly to the south and west in some foothills. He’s retired military and a former cop, so he wants to do the shooting. Assume you’re qualified to do the flight and you have access to a helicopter that can perform this mission safely. The rancher offers to put you up Friday night so you can get an early start Saturday morning.hypoxia lesson plan

You arrive the afternoon before the flight and discuss the flight with the rancher over dinner. It sounds like he’s familiar working around helicopters and doing aerial predator control. After dinner he pours you a scotch and, when you decline it, says something about not letting good whiskey go to waste as he drinks it quickly. He has a few more drinks and puffs on a cigar as you chat into the evening. By the time you head off to bed, he’s slurring his speech slightly.

The next morning he’s up and puffing another cigar while you have breakfast. As you review the plan for the day, you notice the bottle of scotch and figure that he probably had 1 or 2 more drinks after you went to bed. He doesn’t seem to be hung over this morning. As he shoulders his rifle, he asks “We ready?” Can you legally and safely do this flight?

Three things come together in this case: the elevations where you’ll be working are generally above 6,000 MSL. Although this is lower than where most people would be be feeling the effects of hypoxia, at those altitudes there is less oxygen available to breathe (hypoxic hypoxia). On top of that, smoking definitely affects a person’s ability to utilize oxygen (hypemic hypoxia), and so can alcohol (histotoxic). Although this rancher might not be visibly impaired, could residual alcohol in his system further sensitize him to the affects of altitude? In this type of operation–where judgment, reaction time, and a good aim are necessary–is this client prepared to conduct this flight safely and efficiently?

You have a commercial student who’s check ride is scheduled for next week. He’s ready for it, but bad weather has kept him from getting his night solo flights done. It looks like the weather tonight, and maybe tomorrow night, will be above the school’s minimums for night solo flights. As you’re reviewing the student’s pre-flight planning and he’s briefing you on his plan for the flight, you notice he has a bruise and needle mark on his left arm. You make a joke about him getting his heroin habit under control, and he tells you there was a blood drive yesterday at work. The weather turns out to be better than expected, and the student appears to be well-prepared for the flight. Any concerns about sending this student out to wrap up his required night solo flight hours?

The issue here is that night vision can be affected at altitudes as low as 5,000 MSL, and supplemental oxygen has been recommended for night flights at or above 6,000 MSL (although this is not in the current PHAK). In this student’s case, a blood donation can cause a hypemic hypoxia condition that lasts for several weeks. If he’s flying out of a high altitude airport, his night vision could very well be affected by the combination of altitude and anemia.

I think these 2 scenarios are both reasonable and realistic, and can be used to teach students the effects and types of hypoxia closer to the application-correlation level. Are they putting unreasonable expectations on the pilot? Like the SCUBA lesson, these topics are here so that you can evaluate your own fitness for flight, and possibly recognize conditions in your clients and passengers that could affect their comfort or health.

Gross Weight

Winter always brings a bit of weight gain for me. Around mid-October my activity level plunges (less yard work and it gets too nasty outside to run), but my calorie intake stays the same. Of course, there are the Thanksgiving and X-mas binges too. So for the second time in my life I’ve topped 170 lbs. This isn’t overweight for somebody with my build, but it’s about 15 lbs heavier than what I consider my ideal weight. And the last time I was at that weight was about 5 years ago. I like being fit–I look and feel better. But that $65,000 piece of plastic in my wallet is also riding on staying healthy.

Weight gain with aging is a common phenomenon–there’s even a term for it, creeping obesity. Through your mid-twenties, you’re active, pretty fit, and have a pretty high basal metabolic rate. You’re also probably unmarried without kids, underemployed, uninjured, and untethered to a house. As you saddle more responsibility, one of the first things to suffer is the time you set aside for exercise. What doesn’t change is your eating habits–with the affluence of steady employment, your diet is just as likely to get worse than when every grocery shopping trip drained your checking account.

This is basically what’s happened to me. A few years ago I was single and renting a place in Seattle. Technically I was in a long-distance relationship. But I had the free time to train for half-marathons and triathlons. Didn’t matter what I ate, since I was exercising enough that it was difficult to keep weight on. Then I moved, bought a house, gained a spouse-equivalent, and took on some added work responsibilities. Instead of running at lunch, swimming in the evening, and biking or hiking on the weekends, I was doing yard and house work, and spending longer days at my desk studying and working. The gym was an inconvenient 30-minute drive, and my mentality shifted from fueling an athletic goal. I also traveled more, ending up at gluttonous restaurants or eating in airport terminals. We just recently had a kid, and have had a stream of friends and family bringing tasty, fatty meals by. I also injured myself pretty good over-training for a half-marathon, making the long runs and hikes that I’d do all the time impossible.

These are exactly the life changes that contribute to creeping obesity. When I was 155 lbs and first tipped 160 lbs, I wasn’t worried. My pants actually fit better. A couple years later, I was holding a steady 162 lbs. Not too much different than 160 lbs. No worries. Last year I was a stable 165 lbs, with occasional incursions to 168 lbs. This is how it happens. A few pounds a year doesn’t alarm us, but over a 5- to 10-year period, you can be adding a tremendous amount of weight. Each pound is a challenge to take off, and that’s compounded because you’re further cemented into that weight-building lifestyle and less fit. Creeping obesity.

For me 170 lbs is my line in the sand. First off, I’m still flying an R22. I’m hoping to start flying with BoatPix in the spring, and 180 lbs is their limit. In a small helicopter, 10 lbs can make a difference in performance, endurance, and range, and most every employer I’ve talked to over the phone has asked me what my weight is within the first few minutes of our conversation. Every pound I’m carrying is a pound less of paying student that I can fly with. HEMS operators have weight limits for patients, and now they’re starting to put limits on their pilots too. Weight is a big deal for pilots, and your fat ass takes up revenue-earning cargo space.

In addition, weight gain is a symptom of other emerging problems. High-calorie diets and a sedentary lifestyle are gateways to diabetes, cardiovascular/cerebrovascular disease, and the other problems that come with obesity (like obstructive sleep apnea). These can all lead to a medical disqualification. From looking at posts on the forums, and my personal experience with friends and family, the first alarm goes off long after there’s a problem–when the doctor comes back with a diagnosis of metabolic syndrome/high blood sugar, or writes that prescription for blood-pressure or cholesterol meds. The typical course is that people–patients now–continue living the same lifestyle, and adding prescriptions or undergoing surgeries to control the consequent conditions.

That path is unacceptable if you have to sit for a second class medical every 12 months. Weight gain is the first sign that you need to make some lifestyle changes. Maybe in a later post I’ll talk about the lifestyle changes that I’m implementing. Just like a 100-ft altitude or 10-knot airspeed deviation is unacceptable in the cockpit, 170 lbs is an unacceptable weight for me.