Monthly Archives: March 2015

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/

Just how clean is that water container?

If you’re drinking water when recreating (and you should be), how important is choice of container to the cleanliness of the water? Proponents of water bottles certainly show how much easier they are to clean than your average hydration bladder. But does this make a difference?

Well, according to this paper, no. At least not in this convenience sample of people using one of 3 trailheads outside Albuquerque, NM. They were cyclists, hikers, or runners who were simply asked if they could have their water tested. They ended up with only 67, but that was more than they needed based on a power calculation for 20% difference between the two.
The total CFUs for each type was low (37 for water bottles, 27 for hydration bladders), which made finding a difference difficult without a much larger sample size. And even if it had reached statistical significance, such a small difference in colony forming units likely wouldn’t really matter in the real world.

The authors were correct that multiple potential biases could have been present. These include simply lying to the investigators about cleaning methods to appear “better”,  forgetting how long they’ve owned the container, and missing the more “hardcore” athletes who simply wouldn’t stop for the surveys. Most importantly, since these were trails close to civilization, nearly 90% were filled with municipal water that may have slightly disinfected the device.

The main problem I have with this is they didn’t get the water through the tube in the group using hydration bladders. Certainly the rationale was there (trying to avoid contamination from oral flora), but the tubing is the hardest part to clean and thus most likely to be colonized. Future studies should look into a way of controlling for this while measuring the water from the orifice used for consumption.

Based on this study, if you’re recreating near a city using municipal water, it doesn’t matter what type of container you put your water in. Just make sure and clean it regularly. I agree with the authors that applying this data to water that is potentially contaminated is more troublesome. It probably still doesn’t matter, as you should be decontaminating that water via whatever method you choose anyway.

A comparison of bacterial colony-forming units in water bottles and hydration bags among outdoor enthusiasts.
http://www.ncbi.nlm.nih.gov/pubmed/20030447

Think it’s just the flu? Think again.

You learn early in medicine that you will never diagnose a disease that you don’t consider. We all suffer from tunnel vision, and this can result in misdiagnosis and ultimately significant morbidity for patients. Currently most of us are aware of the importance of a good travel history because of the recent Ebola virus outbreak that put everyone on heightened awareness for at least one continent hopping virus.

This is important because clinicians often assume that the acute onset of fever, sore throat, myalgias, headaches, and cough all point towards a diagnosis of influenza or an influenza-like illness (ILI). In many places in the United States, this would result in a prescription for Tamiflu and a discharge home regardless of the results of a flu swab, as it was in the case reported in this article. I’ll not discuss the evidence behind oseltamivir, but the fact of the matter is that patients want it and physicians give it. Nonetheless, the majority of the time the clinician would probably be right (or at least not horribly wrong). Dengue Mar 2 2015

This is all well and good, except that this patient didn’t have influenza. She actually had dengue, which she had picked up on a trip to Haiti that ended 7 days prior to presentation, consistent with the normal incubation period of 3-14 days.

Why does this matter? Because while dengue fever may not be necessarily life threatening, if it progresses to dengue hemorrhagic fever or dengue shock syndrome it certainly carries a worse prognosis. Typically this occurs in those previously infected, so a asking if there has been a prior diagnosis of dengue is also important. Then how do you distinguish between the two?

Clinically, one sign that can point in the right direction is that dengue can cause a truncal rash, which is uncommon in flu. Another vaguely nonspecific clinical finding is a bimodal or “saddleback” fever that persists for 3 days, resolves, and peaks again in 1-2 days. Typically most symptoms resolve in a week, barring severe complications.

Also, apart from dengue titers, most labs are nonspecific in distinguishing dengue from influenza. Both can cause elevations in CPK, transaminases, and the acute phase reactants (ESR and CRP). Both can also cause leukopenia and thrombocytopenia. One finding that is relatively specific is markedly elevated serum ferritin, which can also be elevated for Legionnaire’s disease, another ILI.

In the end, treatment of dengue is no different from that of influenza, mainly supportive care. People infected with dengue are more likely to result in hospital admission, so appropriate suspicion and testing may prevent the “bounceback” patient who ends up getting admitted. Proper diagnosis of dengue is also necessary for epidemiologic purposes. And while your febrile returning traveler might not have dengue either, you still need to make sure their ILI isn’t leptospirosis, MERS-CoV, Legionnaire’s, measles, malaria, meningococcal disease, or typhoid. Thus, keep an open mind, as those hoofbeats might be horses, zebras, or unicorns.

During Influenza Season: All Influenza-Like Illnesses Are Not Due to Influenza: Dengue Mimicking Influenza
http://www.jem-journal.com/article/S0736-4679(14)01439-5/abstract

Additional light reading available at the WHO page on dengue.