Category Archives: mountain

Acute mountain sickness is more than one syndrome

I know what you’re thinking, but I’m not just talking about HAPE and HACE here. But when acute mountain sickness affects up to half of those who ascend beyond 4500m, it’s something we really don’t know as much about as we would like. Currently the definition includes one or more of the following: headache, sleep disturbance, fatigue, and dizziness. This is all scored using the Lake Louise Scoring System. But like with GCS, you can have the same score with a completely different clinical picture. 

One major requirement for acute mountain sickness is headache though. It probably is due to vasogenic cerebral edema causing ICP elevation, as you can measure increases in optic nerve sheath diameter with increases in score.

Sleep disturbance doesn’t seem to be mediated by cerebral edema though. It appears hypoxia mediated, causing an increase in respiratory rate that then causes hypocapnia followed by a compensatory reduction in respiratory drive/rate. This periodic breathing interrupts deep sleep like obstructive sleep apnea does.

Back to the study though. They used 103 participants in the Bolivian Andes, and 189 participants climbing Mt. Kilimanjaro. They were given a survey that had 7 questions about their symptoms. After measuring the VAS by hand, it was plugged into a network analysis tool to find patterns in the data.

What they found were two different clinical syndromes that resulted in three groups of patients. The largest group was those with poor sleep and fatigue but no headache symptoms. The second smaller group had headaches, poor sleep, and fatigue. The smallest group had headache but no sleep disturbance. An interesting tidbit from the study was that there wasn’t a statistical difference between the groups in Bolivia who were randomized to placebo, antioxidants, or Viagra. None of those subjects took acetazolamide or NSAIDs.

Of note, 25 of the subjects in Bolivia were evacuated for severe AMS, but there was only one case of HAPE and no cases of HACE in the entire study. So while they all had symptoms, they perhaps weren’t as bad off as they could have been.

So what does this mean? First, almost everyone at altitude has some degree of fatigue. I like to think it is likely because they weren’t dropped off by a helicopter but instead had to climb to get there, but we have to take the data at face value. However, sleep problems and headaches were distinct from each other with only some overlap. So maybe we should either change the condition we consider AMS, or make different scoring systems for the different pathophysiologic issues. Otherwise you are possibly neglecting one disease process while treating the other. Just like with GCS, you don’t treat everyone with the same score exactly the same, but with the LLS, you might.

Network Analysis Reveals Distinct Clinical Syndromes Underlying Acute Mountain Sickness
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3898916/

Are you using the heel hook? Should you?

As climbing has progressed from simple vertical faces to more complex topography of the rock wall, largely brought on by recreational bouldering, so too have the techniques. One of these is the heel hook. It’s as if the first climber said to him or herself, “hey, that’s like an extra pair of hands down there. Let’s use those!”

And so began at least the documented use of the heel hook, specifically using the back of the heel to put pressure on a hold using your hamstrings. When climbers tell you that you should be using your legs more, they generally didn’t mean this. At least not with gusto, because this paper is a case series of 17 injuries from using this technique.

Heel hook in action

Now, I know what you’re saying. Lower extremity injuries are a small subset of climbing injuries (~5 to ~13%), and most of those are from falls instead of from using the heel as a climbing implement. But this should be looked at more closely, as the authors of this paper state that nearly 2/3rds of their patients were coming for a second opinion due to initial misdiagnosis.

So what injuries do you get from this? All of the climbers in the case series state that while using the heel hook, they had sudden dorsal pain in the knee, thigh, or pelvis. Seven reported a snapping sound as if a ligament had torn. All had a noticeable limp immediately, and point tenderness on exam. With US and MRI, the authors discovered 8 strains, and 9 torn muscles or ligaments. Of note, only 2 required surgery, and the rest were treated conservatively.

Interesting enough is that 6 of the tears were in the pelvis (5 in the biceps femoris alone) in a pattern more common with soccer (football) players,. The 2 knee injuries were similar to those of martial arts injuries from a similar but different heel hook. The velocity there leads to more ACL injuries however.

Prevention is obtained (in the words of the authors) by thorough stretching and flexibility exercises, and a good warmup routine. They also note that people should not use the heel hook ambitiously, as knowing their own limits will prevent injury. They also feel that MRI is not necessarily overkill for pelvic injuries and professional climbers.

The “Heel Hook”—A Climbing-Specific Technique to Injure the Leg
http://www.wemjournal.org/article/S1080-6032(15)00467-6/pdf

So maybe you can use that for a wilderness airway

We’re going to have to talk about the improvised wilderness airway. Caveat: this post is not exactly evidence based. It’s literally an anecdote. But an amazingly good and peer-reviewed anecdote at that. And there is a smattering of evidence thrown in at the end. Typical wilderness airway tool

The case report starts like this: Three firefighters were climbing as part of a team in California when they saw a man falling ~1500ft down a rocky slope. They descended to offer help, and when they got there they removed his helmet, checked ABCs, and maintained his C-spine. Neurologically he was unresponsive. Two emergency doctors with a separate climbing team arrived 15 minutes later. By this time his respirations were irregular and they noted significant facial trauma. Due to gurgling respirations, they decided to perform a cricothyrotomy.

All the physicians had for supplies were climbing equipment and a small first aid kid. They used a pocket knife to make the incision (vertical first, then horizontal), and tubing from a hydration pack as a makeshift ETT. Suture from the first aid kit was used to secure the tube. Since respirations were spontaneous, they did not perform positive pressure ventilations initually.

His pelvis was bound with a pair of pants, and extra clothes were used to prevent hypothermia. After 30 minutes though, his respirations became irregular again. Blood was noted in the tube, so the team decided to create a makeshift positive pressure bag using the rest of the hydration pack. One of the team would blow into hydration bladder to inflate it, and close it off using pliers as a valve of sorts. They would then deliver breaths by squeezing the bladder, similar to commercial products. They used this for another 30 minutes successfully.

Helicopter transport eventually was able to evacuate the man, and it turns out that a 6.5 ETT adapter fit into the makeshift tube easily. A bougie did confirm airway placement, and etCO2 readings were monitored. Unfortunately the patient went into V fib, got ROSC, then went into it again shortly after. The patient never regained pulses after that, and was pronounced dead prior to landing at the hospital.

The most important point of this case report isn’t the cool factor of Macgyvering other equipment into functional airway tools. It’s making the hard decision to perform the cric in the first place. Making that call, even in a low resource setting, is critical. Sadly this patient didn’t survive the injury, but it wasn’t due to lack of an airway. The fact that these physicians were able to also devise and then produce something that gives some form of PEEP is icing on the cake. However, it would be nice if someone took this device and measured what kind of pressures they could obtain with it.

And remember, if you’re going to perform a makeshift cricothyrotomy as your wilderness airway, make sure to use something of proper diameter. Ballpoint pens have too much resistance, but sports bottle and hydration bladder straws will work in a pinch.

Improvised Cricothyrotomy on a Mountain Using Hiking Gear
http://www.wemjournal.org/article/S1080-6032(16)30208-3/abstract

Maybe clothing technology really hasn’t gotten better

Early in the 20th century, explorers were busy trying to reach the poles and climbing mountains, simply because they were there. The casual observer from modern times must wonder how they were able to tolerate such cold temperatures without the high-tech fabrics available today. The mental images of Amundsen, Scott, Peary, and other cold weather explorers are often viewed as men laden with incredibly bulky furs and wool garments. How on earth could they achieve anything wearing that kind of clothing?

Credit: National Geographic/The Wildest DreamThat question has particular merit when considering the legacy of George Mallory and Andrew Irvine. They died in 1924 while attempting to summit Mt. Everest, almost 3 decades before Hillary and Norgay were able to do it successfully. Mallory’s remains were found in 1999 at 8157m, and his clothing was removed for testing before he was buried. After 3 years of intense study using multiple methods, they were finally able to definitively say what he was wearing.

But that only answers part of the question. Now that we know what he was wearing, was it enough to keep him warm but still allow freedom of movement needed to climb mountains? To test this, they simply replicated the fabrics, which were layers of silk, cotton, and wool. This was then covered with an outer layer of gabardine, faithful to the original made by Burberry.

(As an aside, many readers may not be aware of Burberry’s prowess in making clothing for polar expeditions. Like Abercrombie and Fitch, the clothing you can buy today is nothing in comparison to the rugged outdoor items one used to be able to purchase.)

So with that part answered, all that was left was for someone to climb Everest wearing the replica clothing. And Graham Hoyland did just that in 2006. He didn’t summit, but he did learn that the fabrics were light, comfortable, and more importantly, warm enough to use during the day. They were not, however, thick enough to survive a bivouac on the mountain in his opinion.

The part that made the outfit ingenious was the different fabrics of the alternating layers. This allowed decreased the friction between the layers, allowing movement with much less energy expenditure. This was demonstrated when tests comparing Scott’s to Amundsen’s layered garments showed a 20% decrease in said energy doing the same activity when more “slippery” fabrics were used (silk and furs versus wools). The same scientist also showed that Mallory’s fabrics would have been able to protect all the way down to -30C in calm weather.

Sadly, calm weather they did not have. A blizzard came upon them as they approached the summit, and they were last seen on one of the Three Steps. Whether this storm made them turn back or not, it certainly would have predisposed them to hypothermia. As to whether Mallory and Irvine actually summitted? We may never know, unless someone finds Howard Somervell’s camera with proof.

While these findings have done away with the myth that Mallory’s expedition was ill-prepared (based on photos from base camp), what they really show is that modern synthetic fabrics have only incrementally made gains in thermal protection, weight, and function. The argument can be made that tailoring them to fit properly is as important as the material itself.

I wouldn’t try to climb Everest in any modern garment made by Abercrombie or Burberry though.

Mountain Clothing and Thermoregulation: A Look Back
http://www.ncbi.nlm.nih.gov/pubmed/22441098

Additional Readings
http://www.alpinejournal.org.uk/Contents/Contents_2007_files/AJ%202007%20243-246%20Hoyland%20Clothing.pdf
http://www.independent.co.uk/news/world/asia/mystery-at-the-top-of-the-world-did-george-mallory-make-it-to-the-summit-of-everest-before-he-died-2063196.html
http://news.bbc.co.uk/2/hi/science/nature/5076634.stm
https://dspace.lboro.ac.uk/dspace-jspui/handle/2134/9716
http://thewildestdream.com/