Your Captain Speaking: Silent Hypoxia and COVID-19

“Dick, you said you’ve dealt with silent hypoxia as a pilot for 40 years and can recognize it from the other side of the room with COVID-19?”

“Absolutely, Sam. As part of the initial assessment, just by the signs, we can be sure we’re on track. Asking a couple of questions for symptoms just solidifies what we’re dealing with. Here’s the set-up.”

Let’s start with an example. You’re called to a residence by family for a 65-year-old who’s not feeling well. PPE donned, you enter the living room for your first general impression of the patient. The man is seated and looks up at you as you enter—in fact, he gives you a little wave hello. You take a moment and notice his respiration rate is fast—about 30-plus a minute. There’s a hint of a blue tinge around his lips, and as you get closer you check out the fingernail color: blue—cyanotic. The family says their father hasn’t been feeling well, but when asked about shortness of breath, he denies any.

A high respiration rate and not feeling short of breath? That’s odd. And then a check of his pulse-ox level causes a double-take. “Samantha, did you say the pulse ox is 67?!”

Really? A very functional patient who is alert, not short of breath, with signs of cyanosis and maybe a bit of a fever. Not every patient is going to present like this, but early in the COVID-19 disease, you can see “silent hypoxia” if you’re looking for it. Then you can quickly narrow down your decisions about treatment and how to protect yourself.

Hypoxia in Pilots

Pilots who fly at high altitude are alert for silent hypoxia every flight. Here’s the training drill when you go into the altitude chamber (few nonpilots have ever been there!):

Simplified, the altitude chamber is an airtight chamber where you put people inside and suck the air out to simulate a high altitude. Most training sites are at sea level, so they gradually raise the chamber pressure to the equivalent of about 20,000 feet. A normal airline cabin goes up slowly as well and is often in the 6,000–8,000-foot range while cruising, so this is much higher.

Above 14,000 feet pilots must be on supplemental oxygen. I have my helmet on but am not wearing my O₂ mask.

After a few minutes in the chamber, we are given some tasks. Simple ones, really, but when you’re hypoxic they are tough. “How many nine-cent stamps in a dozen?” It was about the eighth question, and I recall writing an answer, then crossing it out and writing another. I’m really good with math and for years have known one of my hypoxic symptoms is an inability to do it. I could converse just fine—in fact, I was very happy. My respirations were rapid, but I never felt short of breath. A pulse oximeter would have shown I was in the 60%–70% range. If I had taken off my flight gloves, I might have noticed my fingernails were blue. Or maybe not. It was slow enough that I adapted just fine.

This kind of hypoxia is sometimes called “happy hypoxia.” There is nothing happy about it, but it’s called that because the pilot/patient is content and even giddy. They will laugh for no reason and think everything is just fine. They are in danger.

Conclusion

Back to our patient: As you do your general assessment, often from across the room, if you can spot a high respiration rate, look closely for cyanosis. If your pulse oximetry readings are low enough to make you wonder if the machine’s broken, consider COVID-19.

Dick Blanchet (ret)., BS, MBA, worked as a paramedic for Abbott EMS in St. Louis, Mo., and Illinois for more than 22 years. He was also a captain with Atlas Air for 22 years and an Air Force pilot for 22 years.

Samantha Greene has been a paramedic, field training officer, and operations supervisor for Abbott EMS of Illinois for the last 10 years and a lieutenant for the Madison, Ill., Fire Department for the last five.