Category Archives: Altitude

Deep breathing to prevent AMS

Mountain sickness can effect even the fittest among us. It is so prevalent that there are myriads of studies showing the lowest effective dose of acetazolamide, as it has unwelcome side effects. While other studies have shown that ibuprofen is effective without the side effects, these authors wanted to see if they could prevent AMS with simple breathing techniques.

They chose to do it with an unusual group of study participants as well. Usually, you get relatively healthy people who you know can complete the activity. They instead chose to use a group of nonathletes, all of which had almost no climbing experience. Going from 1970 m to 5895 m is quite a challenge, even if the terrain isn’t terribly technical. Many had medical problems that would typically preclude them from study, such as MS, RA, and metastatic cancer. Needless to say, this is not a group most would expect to be able to climb the peak successfully.

And yet they did, doing so in only 48 hours, instead of the usual 96+ hour climb. Also of note, they had a 92% success rate, much higher than the 61% success usually achieved. None of their group had any symptoms of severe AMS, and the 4 that had moderate AMS based on the Lake Louise Scoring System subsequently went back down to mild AMS after a 30 minute “breathing session.” 1 patient did have suspected HAPE, that resolved with descent and nifedipine.

How did they achieve such great results? The authors state that they were using the Wim Hof method, named after Wim Hof, of course. This is defined as mindset coaching, cold exposure, and breathing technique practice. Their methods section, lacking as it is a letter to the editor, doesn’t mention how long they trained before the ascent, just that they did. Mr. Hof’s own website advertises a 10 week video course. Of note, there is another study about the anti-inflammatory effects of this method as well, and their training was only 10 days in length.

At face value, it seems like the training was effective. This is balanced with the nigh unbelievable nature of the claims made by Mr. Hof and other proponents of his method. While I don’t want to dismiss this completely, I would argue that further studies certainly need to be performed before I recommend this method. On the other hand, you can (apparently) learn the method for free, and if you want to try it and take pharmacologic backup on your next climb, then the harm in trying is likely very low.

Controlled Hyperventilation After Training May Accelerate Altitude Acclimatization
http://www.wemjournal.org/article/S1080-6032(14)00116-1/abstract

Predicting survival after avalanches

More than 150 people die each year after being buried in an avalanche, and mortality is greater than 50% for this condition. Unfortunately, a large amount of resources are used on patients who ultimately expire, so determining which ones are likely to survive can safe costs and allow better utilization of resources such as extracorporeal life support (ECLS) warming and air evacuation.

Of the 3 common causes of cardiac arrest after avalanche, only hypothermia is likely to have good outcomes. Trauma and hypoxia have poor outcomes. Most algorithms have providers stop resuscitation for severe trauma, and airways packed with snow. However, ascertaining hypoxia vs hypothermia is less obvious. Prior attempts used potassium >10 mmol/L or >12 as a surrogate marker for cellular death from hypoxia, but no other markers are used.

So these authors took 20 years of data from the North French Alps, which ended up being only 48 patients with cardiac arrest.  18 of them had ROSC pre-hospital, and only of those 2 were eligible for ECLS. 19 of the 30 without ROSC were also eligible for ECLS. In total, only 8 survived, 5 from the pre-hospital ROSC group, and 3 from the non-ROSC. Of the 8 survivors, only 3 had favorable neurologic outcomes.

All of these were patients with rescue collapse, that is loss of vital signs after extrication or transfer. 3 other patients with rescue collapse died however. Other indicators for survival in their analysis are the presence of a rescue pocket, K <4.3 (nobody survived above 4.2, but some nonsurvivors had levels below this), and coagulation disturbances. Interestingly, their data showed no overlap of prothrombin time between survivors and non-survivors, but they sadly did not give the values, only as ratios. Other values such as PaO2, PaCO2, lactate, and bicarb are not predictive.

Unfortunately, for such a long time period of collections, there were very few survivors. The retrospective nature also limits analysis. It does look like we need to reduce the cutoff for resuscitation from values of K from 10-12 mmol/L to a lower number (7?). Also, identification of coagulation abnormalities may help. Perhaps POC thromboelastograms may be a way to identify those that do not merit resuscitation.

Survival after avalanche-induced cardiac arrest
http://www.ncbi.nlm.nih.gov/pubmed/24971508