Research: Right temporal cerebral dysfunction heralds symptoms of AMS

I just read through an article written in 2007 today that found specific features in scalp EEG data, measured at moderate altitude, might predict the occurrence of AMS. You can download the study from the web if you have access to PubMed. I have put the abstract and title of the article at the bottom of this blog entry.

In their study, the authors investigated AMS in relation to brain function, cerebral blood flow, and end-expiratory CO2 and found effects related to AMS in the right-hemisphere scalp EEG. Supportive of this EEG finding are correlated changes in expiratory CO2 and an increase in cerebral blood flow velocity in the right middle cerebral artery.

Notably, changes in the EEG that were determined to be related to AMS occurred before changes in cerebral blood flow and end-expiratory CO2. (Significant changes in the EEG occurred before changes in the cerebral blood flow and end-expiratory CO2.)  Hence, changed EEG at moderate altitude might be a good way to identify who will get AMS at high altitude.

While the study showed some encouraging results, the study also has some weaknesses that can be addressed with some replication and some data processing modification. The main weaknesses of the study are: (1) the low number of participants that participated in the study beginning to end (22, at most) and (2) the low significance threshold of 0.05 (for the number of comparisons) that was used. In addition, data plotted in the paper show that for a few participants, the effect of altitude on the EEG was in a direction that was inconsistent with the group.  This inconsistency could be artefactual in nature and could arise for a number of reasons unrelated to brain function.  A replication of this study would add weight to these findings and offer an opportunity to investigate EEG processing methods that are less susceptible to noise.

Hence, it is worthwhile to do further investigation of EEG as a predictor of AMS in various circumstances, at a variety of altitudes, and investigate how varied training regimes prior to ascent modulate the likelihood of occurrence of AMS.

The abstract and author information obtained from PubMed is given below.

J Neurol. 2007 Mar;254(3):359-63. Epub 2007 Mar 7.

Right temporal cerebral dysfunction heralds symptoms of acute mountain sickness.
Feddersen B, Ausserer H, Neupane P, Thanbichler F, Depaulis A, Waanders R, Noachtar S.

Source

Department of Neurology, Klinikum Grosshadern, University of Munich, Marchioninistr. 15, 81377, Munich, Germany. berend.feddersen@med.uni-muenchen.de

Abstract

Acute mountain sickness (AMS) can occur during climbs to high altitudes and may seriously disturb the behavioral and intellectual capacities of susceptible subjects. During a Himalayan expedition 32 mountaineers were examined with electroencephalography (EEG) and transcranial doppler sonography (TCD) to assess relative changes of middle cerebral artery velocity in relation to end-expiratory CO2 (EtCO2), peripheral saturation (SaO2), and symptoms of AMS. We tested the hypothesis that O2 desaturation and EtCO2 changes precede the development of AMS and result in brain dysfunction and compensatory mechanisms which can be measured by EEG and TCD, respectively. Contrary to our hypothesis, we found that subjects who later developed symptoms of AMS between 3,440 m and 5,050 m altitude exhibited an increase of slow cerebral activity in the right temporal region already at 3,440 m. Cerebral blood flow increased in these mountaineers in the right middle cerebral artery at 5,050 m. These findings indicate that regional brain dysfunction, which can be documented by EEG, heralds the appearance of clinical symptoms of AMS.

Research: Why revelations have occurred on mountains? Linking mystical experiences and cognitive neuroscience

I found yet another interesting article while investigating the effects of high altitude on brain function. However, this time the article is of a more spiritual nature; the article describes how anoxia can impact specific parts of the brain and cause a knock-on spiritual experience. This is an interesting and entertaining read. Find and download this article. And if you're wondering, I do have a spiritual side. (link)


Why revelations have occurred on mountains? Linking mystical experiences and
cognitive neuroscience

Shahar Arzy a,b,c,*, Moshe Idel d, Theodor Landis b, Olaf Blanke a,b
a Laboratory of Cognitive Neuroscience, Brain-Mind Institute, Ecole Polytechnique Fe´de´rale de Lausanne (EPFL), Lausanne, Switzerland
b Department of Neurology, University Hospital, Geneva, Switzerland
c Department of Neurology, Hadassah Hebrew University Hospital, Jerusalem, Israel
d Faculty of Humanities, Hebrew University, Jerusalem, Israel
Received 26 March 2005; accepted 21 April 2005

Summary:

The fundamental revelations to the founders of the three monotheistic religions, among many other revelation experiences, had occurred on a mountain. These three revelation experiences share many phenomenologicalcomponents like feeling and hearing a presence, seeing a figure, seeing lights, and feeling of fear. In addition, similar experiences have been reported by non-mystic contemporary mountaineers. The similarities between these revelations on mountains and their appearance in contemporary mountaineers suggest that exposure to altitude might affect functional and neural mechanisms, thus facilitating the experience of a revelation. Different functions relying on brain areas such as the temporo-parietal junction and the prefrontal cortex have been suggested to be altered in altitude. Moreover, acute and chronic hypoxia significantly affect the temporo-parietal junction and the prefrontal cortex and both areas have also been linked to altered own body perceptions and mystical experiences. Prolonged stay at high altitudes, especially in social deprivation, may also lead to prefrontal lobe dysfunctions such as low resistance to stress and loss of inhibition. Based on these phenomenological, functional, and neural findings we suggest that exposure to altitudes might contribute to the induction of revelation experiences and might further our understanding of the mountain metaphor in religion. Mystical and religious experiences are important not only to the mystic himself, but also to many followers, as it was indeed with respect to the leaders of the three monotheistic religions. Yet, concerning its subjective character, mystical experiences are almost never accessible to the scholars interested in examining them. The tools of cognitive neuroscience make it possible to approach religious and mystical experiences not only by the semantical analysis of texts, but also by approaching similar experiences in healthy subjects during prolonged stays at high altitude and/or in cognitive paradigms. Cognitive neurosciences, in turn, might profit from the research of mysticism in their endeavor to further our understanding of mechanisms of corporeal awareness and self consciousness.

Research: General introduction to altitude adaptation and mountain sickness

I just read through a research paper written by Bärtsch P., Saltin, B. General introduction to altitude adaptation and mountain sickness. Scand. J. Med. Sci. Sports 2008 (Suppl. 1):1-10.

I have put a few excerpts from the paper into this blog to inform my fellow climbers.  The text below is a mixture of paraphrasing and quotes from the paper.  This is a really good paper and I highly recommend tracking it down and giving it a complete read.

Abstract

The key elements in acclimatization aim at securing the oxygen supply to tissues and organs of the body with an optimal oxygen tension of the arterial blood. In acute exposure, ventilation and heart rate are elevated with a minimum reduction in stroke volume. In addition, plasma volume is reduced over 24–48 h to improve the oxygen carrying capacity of the blood, and is further improved during a prolonged sojourn at altitude through an enhanced erythropoiesis and larger Hb mass, allowing for a partial or full restoration of the blood volume and arterial oxygen content. Most of these adaptations are observed from quite low altitudes [1000m above sea level (m a.s.l.)] and become prominent from 2000 m a.s.l. At these higher altitudes additional adaptations occur, one being a reduction in the maximal heart rate response and consequently a lower peak cardiac output. Thus, in spite of a normalization of the arterial oxygen content after 4 or more weeks at altitude, the peak oxygen uptake reached after a long acclimatization period is essentially unaltered compared with acute exposure. What is gained is a more complete oxygenation of the blood in the lungs, i.e. SaO2 is increased. The alteration at the muscle level at altitude is minor and so is the effect on the metabolism, although it is debated whether a possible reduction in blood lactate accumulation occurs during exercise at altitude. Transient acute mountain sickness (headache, anorexia, and nausea) is present in 10–30% of subjects at altitudes between 2500 and 3000ma.s.l. Pulmonary edema is rarely seen below 3000ma.s.l. and brain edema is not seen below 4000ma.s.l. It is possible to travel to altitudes of 2500–3000ma.s.l., wait for 2 days, and then gradually start to train. At higher altitudes, one should consider a staged ascent (average ascent rate 300 m/day above 2000ma.s.l.), primarily in order to sleep and feel well, and minimize the risk of mountain sickness. A new classification of altitude levels based on the effects on performance and well-being is proposed and an overview given over the various modalities using hypoxia and altitude for improvement of performance.

Definitions:


Erythropoiesis is the process by which red blood cells (erythrocytes) are produced. It is stimulated by decreased O₂ in circulation, which is detected by the kidneys, which then secrete the hormone erythropietin. This hormone stimulates proliferation and differentiation of red cell precursors, which activates increased erythropoiesis in the hemopoietic tissues, ultimately producing red blood cells. 

Notes of Interest:

A significant increase in red blood cell mass may already occur after 3 wees at a minimum altitude of 2100 m a.s.l. (Schmitd & Prommer, 2008) and this gets more pronounced as altitude increases.

During the first 24-48 h, at even a low altitude (15000-2000 m a.s.l.), Hb concentration is elevated by 0.5-1.0g/100 mL blood, which may correspond to a loss of plasma water of 0.2-0.3 L.  At 3000 and 4000 m a.s.l., the rise in Hb concentration may amount to another 0.5-0.8g/100 mL per 1000m, indicating a decrease in plasman volume of 0.600.9 L (Saltin, 1966; Svedenhag et al., 1997; Calbet et al., 2004).

Classic high-altitude training involves living and training at altitudes between 2000 and 2800 m a.s.l. for a period of 2-4 weeks.  Living high and training low, introduced by Levine & Stray-Gundersen (1997), consists of living about 20h/day at an altitude of 2800 m a.s.l. and training at an altitude of 1200 m a.s.l., which already impairs maximum aerobic performance in well-trained subjects.

AMS (Acute Mountain Sickness)

There appears to be a threshold altitude of about 2100 m a.s.l. for significant development of AMS (acute mountain sickness) with exposure to hypobaric hypoxia at rest (Muhm et al., 2007).  At altitudes between 2500 and 300 m, the prevalence of AMS is betwen 10% and 30%, depending on the population and the definition of AMS.  At these altitudes, AMS is usually mild, transient, and does not progress to more severy symptoms of altitude illnesses, such as cerebral or pulmonary edema. [PHIL: note, they say nothing about cognitive function or neuronal damage].  At altitudes of 4000 - 4500 m a.s.l., the prevalence of AMS is 40%-60%, and in some susceptible individuals treatment with oxygen, dexamethasone, and descent ar necessary for improvement and prevention of progression to cerebral edema (Bärtsch & Roach, 2001).  When going to altitudes above 3000m, staged ascent and /or prevention of AMS by acetazolamide (2 x 250 mg/day may be necessary to avoid physical discomfort within the first few days of altitude exposure.  A low hypoxic ventilatory response (HVR) may be associated with increased susceptibility to AMS (Moor aet al., 1986; Richalet et al., 1988a), and HVR tends to be lower in endurance-trained athletes (Schoene, 1982). [PHIL: This means that if you're an endurance-trained athlete, it is a good idea to learn how to breath properly for a trip to the top of Kilimanjaro.)

The text below discussing HACE and HAPE comes directly from Bärtsch & Saltin, 2008.

HACE (High-Altitude Cerebral Edema)

HACE is usually preceded by progressive symptoms of AMS. It is characterized by progressive truncal ataxia, clouded consciousness, and variable focal neurologic symptoms. Without treatment, coma usually develops within 1–2 days, and death occurs rapidly because of brain herniation. Vasogenic edema has been demonstrated by MRI (Hackett et al., 1998). Treatment consists of administration of supplemental oxygen, dexamethasone, and descent. HACE rarely occurs below 4000ma.s.l. (Fig. 2), and the prevalence at 4000 5000ma.s.l. is 0.5–1.5%. HACE can be avoided by preventing AMS or by fast and adequate treatment of AMS.

HAPE (High-Altitude Pulmonary Edema)

HAPE is a non-cardiogenic edema that is due to a non-inflammatory capillary leak caused by an abnormally high hypoxic pulmonary vasoconstriction (Bärtsch et al., 2005). Early symptoms are dyspnoea, decreased performance, and cough. In advanced cases, dyspnoea at rest, orthopnoea, and pink frothy sputum occur (Bä rtsch, 1999). HAPE is rare below 3000ma.s.l. and is usually associated with abnormalities in the pulmonary circulation. Prevalence of HAPE after rapid ascent to 4550ma.s.l. within 24 h, including an overnight stay at 3600m a.s.l., is 6% in a general mountaineering population (Fig. 2) and 60–70% in HAPE-susceptible individuals (Bärtsch et al., 2002). Susceptible individuals are characterized by an abnormal increase in pulmonary artery pressure with exposure to hypoxia and also during normobaric exercise (Grünig et al., 2000). This abnormal response pattern of the pulmonary circulation can be found in about 10% of the population in Germany (Grünig et al., 2005). The rate of ascent, the altitude of exposure, and exertion are the major risk factors for development of HAPE, in addition to individual susceptibility based on an abnormal pulmonary hypoxic vasoconstriction. HAPE can be avoided in susceptible individuals with slow ascent (300–400 m/day above 2000ma.s.l.). If slow ascent is not possible, HAPE can also be prevented by drugs that lower pulmonary artery pressure, such as nifedipine (Baürtsch et al., 1991), sildenafil, or dexamethasone (Maggiorini et al., 2006). Treatment consists of administration of supplemental oxygen, application of pulmonary vasodilators (nifedipine or tadalafil), and descent. Mortality is estimated to be 50% if no treatment is possible (Lobenhoffer et al., 1982), while adequate treatment leads to a complete recovery without sequelae.

Physical Preparation to Ascend Above 5000 Meters

I've been doing quite a bit of reading on the topic of the effects of high-altitude on brain and body.  Data collection for this type of research generally takes one of three contexts: (1) in a hypobaric chamber where the air pressure is artificially reduced, (2) on a mountain during an ascent, and (3) at a 'base' air pressure in a 'before' vs. 'after' comparison.  Each context has its advantages and disadvantages.  What this research tells us is what happens on average.  And many of us like to think of ourselves as "better than average".  Take a minute to decided if this is actually the case and if we might consider following recommendations derived from average people.

I assume that each person ascends Kilimanjaro with the expectation that their brain and body will continue to function as it did before they started.  I think this is the expectation for any extreme sport-- that we won't become permanently injured. I have had my share of injuries and fortunately I think I've fully recovered from most of them.  What is common to all extreme sports is the inherent risk of injury; those of us who undertake these activities accept risk as our way of life. What is clear from the research I have read is that we will encounter a significant reduction in the oxygen available to our brains and bodies.  While this is well-known, it is not well-known how each of us individually will be affected by the reduction in oxygen and and air pressure and how each of us will 'bounce-back' from oxygen deprivation.  The research is clear that above 5000 meters (5000 is a nice round number), for those of us essentially starting at sea-level, on average the risk increases.  That said, their are many individual variables to account for that have an impact on the calculation of one's own individual risk such as the duration of time above 5000 meters, the physical preparation beforehand, our own genetic dispositions, and so on.  The list is long.  It would be extremely valuable to have a little machine in our pockets that could tell us our individual likelihood of returning home with an injury. One day such a device might exist.

The human body is an amazing machine that ultimately gets stronger when you work it, within reason.  When a buddy and I rode our bicycles 7600 km in 57 days to cross Canada in its entirety, various bike parts wore out but our feet, legs, and knees got stronger.  With the goal of completing this challenge and coming out stronger than we were, we must strive to be at our physical best before making the ascent and we must be wise in our activities on the mountain.  "Pole, pole", they say.

Requesting community support to spread the word: link and share

Hello everyone (friends, colleagues, and fellow adventurers)

My colleagues and I will be heading up Kilimanjaro this Fall to have an extraordinary adventure. In addition to reaching the summit, my plan is to bring some equipment up with me to study brain and body changes related to the high-altitude ascent. Given climbers volunteer to participate in the study, I will write-up some some interesting research papers.  In addition to all of this, I plan on putting together a video documentary of the trip. (This is of course all depends on the weather, and the physical and emotional obstacles that will be encountered.)  In any event, for the purpose of bringing arm-chair adventurers, outdoors persons, and other curious people together, we would like to create a lot of publicity around this excursion.  If your are a supporter of mountain adventure, please share this blog with your friends and colleagues.  I'll do my best to keep it updated and share any interesting and humorous video as we get closer to the start date of our African safari and our trek up Kili.

Thanks to all of you,

Phil

Hero HD camera - my ride to the Stepforth Web Marketing office

Today was my first attempt recording video using the Hero HD camera.  I purchased one yesterday to use on our Kilimanjaro expedition coming this Fall.  If you take a look at the video, you can see the picture quality is quite good recorded at 1080p @ 30fps.  However, you'll also notice that there is quite a bit of vibration/jitter in the video and by the looks of it, jitter removal algorithms will have some difficulty removing jitter at 30 fps. (The low sampling rate and camera vibration caused by my bicycle tires inflated at 120psi causes jumps in the video that are greater than just a few pixels.)  Fortunately, I can bring the sample rate up to 60 fps however with a reduction in video resolution to 960p.  I'll try this next time and apply a jitter removal algorithm and see what I can get.

Overall, I'm happy with the quality of the camera and the various helmet and body mounting accessories.  We'll soon see how well it operates at -30 C when we do the freezer test on our equipment.  I'll post video of some of my research team and I in a walk-in freezer in the weeks to come.

Incidentally, if you run the video posted above to the end, you'll notice that I arrive at the Stepforth Web Marketing office on my ride into work each day.  When I started my company ABVSciences, Ross Dunn at Stepforth provided me with a desk and space for my computer equipment.  I still spend each day with the Stepforth gang.  From my point of view, I've gained a tremendous amount of knowledge about marketing on the internet and web and search engine optimization by being in their environment and collaborating on the future of marketing.  Thanks Ross, you've become the official web marketing sponsor for this trip!!

Brain activity at 5,895 metres (19,341 ft) above sea level

The other day my research colleagues and I where throwing around some fun ideas about combining our professions with some of our day-to-day activities.  Myself: I'm a scientist and developer of new signal processing technologies and methodologies to better understand brain disease and function. I'm also an avid outdoors man and weekend warrior.  The colleagues in the room at the time of this discussion also boast a fine mixture of scientific curiosity and enjoyment of the outdoors. Together, we came up with this crazy notion: use an Emotiv EPOC EEG headset to measure brain function during the ascent to the top of Kilimanjaro.  "I'll do it!", was my response.

The plans are not yet concrete and we have some technical issues to figure out but it looks like this is actually going to happen.  We'll be doing a "technical" test to see how feasible this will be in a 'race' held on the 16th of July near Victoria, BC, Canada (http://www.facebook.com/finhike).  The objective of this 'race challenge' is to see who, out of those persons entered, can go up and down Mnt. Finlayson the most times in 12 hours. (It is just crazy enough to get my attention.)

Our "Climb Mount Kilimanjaro" Facebook page: https://www.facebook.com/home.php?sk=group_167598523287675&ap=1