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.