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Hello. Welcome to the endeavor. Medical talk on high altitude illnesses. I'm John Dalam or and I'm going to introduce myself and tell you a little bit about my background before we launch into the talk. I work as a GP in the Wye Valley, and for the last 25 years I've worked as a specialty doctor in the emergency Department of Pastoral Infirmary. I retired from the N H s in 2020 but with the pandemic, I returned to work a couple of weeks later and have continued to work as a GP and in the emergency department. So a rather unsuccessful retirement. I'll continue as a senior lecturer at the University of Bristol. I've been advising medical students on the medical aspects of the electives since 2003, and in 2007, I became an International mountain leader. I've been on many expeditions. I've spent more than two years in the field looking after groups, either as a doctor and or a leader in Mountain jungle desert and Arctic environments. With James More, I set up the diploma expedition in Wilderness Medicine at the Royal College of Physicians and Surgeons of Glasgow in 2005. Sorry, 2015. I'm a clinical teacher on the UK diploma in mountain Medicine and have been teaching on that since I completed it myself in 2004. The big project over the last couple of years has been as the lead edit er of the O. U P Handbook of Expedition and Wilderness Medicine, uh, now in its third edition, and that's gone to the publishers and is in press. Hopefully, it will be available in late 2022. For more than 25 years, I've been, uh, fellow at the Royal Geographical Society and have been part of the expedition. Medical Cell will challenge the youth expedition Company has been running, uh, since early 1990 I've been the advisor for now, almost 30 years, most recently during lockdown and during the pandemic. I've taken over the role as medical officer to seven area Rescue Association, which means that I get involved in Cliff River, uh, lifeboat operations together with land searches. So the aims of today's session on high altitude dialysis is to increase your understanding of altitude when working with groups and hopefully to make you feel more confident to deal with those people who become unwell as a result of exposure to high altitude, I'm going to start with a short scenario to make you think I'm going to talk about different important high altitude illnesses. And the prevention strategies briefly touch on the risks of high altitude trekking. And then we'll look at the changes that have occurred to the Lake Louise score and look at treatment and I'll tie that in with the latest W. M s guidelines, which were published at the end of 2019 so straight away, let's go to East Africa to Kilimanjaro. As many of you will know, that 5895 m it's the highest free standing mountain on Earth and at one time about half the deaths in the world from altitude illnesses occurred on Kilimanjaro and Mount Kenya. And that's because you're able to go very high very quickly. Some of you may have been to Kilimanjaro already, but it's a place where many budding expedition doctors will cut their teeth with altitude related problems by a company in groups and Kibo hut is high on the mountain just before the krater rim, where many groups will go to rest the night before they reached the summit. So let's talk about Bruce, who's a 45 year old tracker who's undertaking the meringue goo track. So this is the so called tourist or Coca Cola root, which goes up Kilimanjaro. You start off at meringue goo, uh, at 2700 m and then go to Mandiri and from Mandera you go to Haram Bow. And because he's in a developing world country, Bruce has unfortunately developed diarrhea, which is very common, and he starts to take some antibiotics. But he's already unwell, and by the time he reaches Kibo heart at 4700 m, um, he's now very, very slow. It's always useful to look at the ascent profiles for any mountaineering expedition. So if we look at the ascent profile for the more anger route, you can see that at the gate you start off at about, um, 1800 m and then go to 2700 m 3700 m 4700 m and then to the summit. So this means that some people will go from 1800 m to 5895 m over the course of just three days, so they'll attempt to to some it on the morning of the fourth day before descending quite quickly to go back to the park gate. As the expedition medic, You're probably already aware that Bruce has been struggling that he's perhaps self treating with antibiotics for diarrhea. And by 4 30 in the afternoon, you recognize that he's unwell. And on further questioning, you find out that he has a moderate headache. He throws up a couple of times, he feels lightheaded, and all he wants to do is to go and sleep in the hut. And I just want to put the question out there, maybe have a think about this. What are you going to do in this situation as the track medic? We're on the equator. It's going to be dark, really. By half past six, you've only got a couple of hours of daylight. You've got lots of things to think about in this sort of case. Are we going to watch and wait? We're going to send them down straight away we're going to think about medication, lots of potentials. And, uh, I hope to make it clearer during the course of this talk how we might cope with Bruce or other patient's in similar situations in high altitude environments. Let's go on then and look in more detail at common important high altitude illnesses. Different elevations have been defined as high or extreme altitude. So from around 2500 m up to 3500 m, this is defined as high altitude. Above that, up to around 5500 m is very high altitude. And then we're looking at extreme altitude up too. 8000 m and then the so called death zone, Um, over 8000 m, where permanent survival, um, without supplemental oxygen is simply not possible. So you may ask, where in the world is high? Well, here's a good test of geography. There are lots of high altitude areas, some of which I guess you perhaps don't know, and I'm going to just point out a few of these on the on the map. But we've got the Rockies going from, uh, west to east and and the Andes. There are some peaks in the Arctic, which go up to around 3000 m. And then, of course, you're familiar with the Alps, perhaps the high Atlas Mountains in North Africa. In West Africa, there's Mount Cameroon. In East Africa, you've got Aunt Kenya and Kilimanjaro. In South Africa, there are the Drakensberg Mountains. You've got Mount Dermabond in Iran and the Simeon Mountains in Ethiopia. Obviously, there's the Himalayas. We've got Mount Albarus, the Tatras in Poland, and as you go further east, we've got Carstens Pyramid, which is one of the seven summits, the highest one of the highest points in each of the continent's Mount Cook in New Zealand. And obviously you've got Mount Vincent done in Antarctica, so lots of places for you to consider if you're going to high altitude. Interestingly, when trekking at high altitude, the changes the physiological changes begin to occur at around 1500 m, and that's because less oxygen is available as the barometric pressure drops as you go higher. Those who ascend rapidly to around 2000 m, then altitude illnesses are quite common, but and most importantly for expedition medics, most people can adapt to altitudes above 5000 m, provided they have enough time. Let's think about some of the path of physiology. So as you ascend, clearly the air pressure is lower and the partial pressure of oxygen, therefore, is less. Remember that the concentration of oxygen the percentage remains at 21% but the partial pressure is lower, so there's less available oxygen with each breath and to compensate. Breathing becomes faster and deeper, and the heart beats faster. Over time you develop more red blood cells. But one of the early changes, which occurs in terms of acclimatization, is the right word shift of the Oxygen's Association curve. So this means that hemoglobin gives up oxygen more readily to the tissues, and that's due to changes in 23 d. P. G. I'll come back to that in a moment. This slide just shows the barometric pressure at different altitudes, and you can see that by the time you reach the summit of Everest without supplemental oxygen, then the partial pressure of oxygen is around one third of what it would be at sea level. If your leverage space camp, it's around 50% of what you find at sea level. You'll remember this from medical student days. But the curve the sigmoid curve, shows you p 02 on the X axis and, um, saturations oxygen saturations on the Y axis, and you'll know that certain things will shift the curve to the right or to the left. But there's a rightward shift with acclimatization, which means that the hemoglobin has reduced affinity for oxygen, which means that it's more readily released to the tissues. And that's one of the most important and early changes that occurs with acclimatization. I've seen a lot of effects of altitude in my time. I've probably worked with between four and 500 clients or potential patient's um over 4000 m. Um, the vast majority of people going above 3 to 4000 m will get some symptoms, but for many, it's just a minor problem. But for a few, um, and I've seen a few seriously unwell people. Altitude in this is very dangerous, and one of the reasons that people get into trouble is that they're not honest with themselves or with you as the medic about their symptoms. There's sometimes enormous emotional pressure to keep going, and you might like to to pause and think for a moment about why people are so, um, pressured into into reaching the summit. And it could be that, uh, this is for a charity. There's peer group pressure or it may be that they are going to remember a loved one. And reaching the summit is very, very important for emotional reasons, which may then cloud people's judgment, Um, and also mean that they may ignore some of their symptoms. And that's sometimes very difficulty to manage, as as an expedition medic to the sorts of symptoms that patient's will get are they're out of breath. They have headaches, they go off their food and they don't sleep very well. And this is acute mounted sickness. But if AMS is severe and people keep going up, then pulmonary edema and cerebral edema can develop, and both of these conditions can be life threatening. There are some other changes which occur. Many people will experience an increase in urine output. Some have poor balance. And if you're operating in more technical mountainous terrain and that can be difficult, and sometimes people also get changes in in eyesight as well as I say, acute mountain sickness tends to occur above about 2500 m. The symptoms appear gradually 6 to 12 hours after arrival at high altitude. And then if you don't go any higher, then they'll normally just settle as the body acclimatize is to the reduced, uh, partial pressure of oxygen. How big a problem is it? Well, they've been quite a lot of different studies on the incidents of AM s. Certainly we know that it's rare, very rare below 2500 m, but those who travel rapidly to 3500 m or higher will get symptoms. If you go up, um, the Aggie Domini in Shamkhani, you may find that some people who travel up in the cable car can feel quite lightheaded and unwell. With that rapid ascent in the in the cable car, Soma Guerini, in 1990 found incidence rates of 9% at 2850 m, 13% at 3050 and 34% at 3650 m. Hahn Igman did some studies found similar figures. Um, in Colorado. Hackett did some early work. Um at Fritsche found incidence rates of around 43%. Um, but a Bosnia in 2000 found that goes Ankunda. Pilgrims traveling to 40 Sorry, uh, 4300 m had an incidence rate of around 68% but they were rapidly traveling to that altitude because they were going by bus. Kilimanjaro has very high rates of, um, am s, um and again around 52% at the South Pole. And that's partly because the barometric pressure there is so much lower, even though it's not very high. And that's because you get changes in the barometric pressure at the polar regions. I published some research on the incidence of acute mountain sickness in adolescents. I wanted to look at this particular group of travelers and I studied 52 teenagers doing identical ascent profiles on Mount Tuggle at 4186 m in the Atlas Mountains in North Africa. And I found that the daily incidents of AMS in these students, uh, was between 3% and 42% and obviously increased with altitude. And what was interesting in this particular study is that girls had a statistically significant higher incidents of AM s. Um, that may or may not have been because they were more happy to report their their symptoms. Um, but that's that's perhaps for a discussion when we need. As I said, the main symptoms of acute mountain sickness are headache, tiredness, poor appetite, sometimes nausea, being dizzy or lightheaded, and changes in sleep. And for many years, these main symptoms of AMs have been recorded on a scorecard, and from 1993 this was called the Lake Louise score. Each of these five symptom groups a scored 0123. None mild, moderate or severe. And clearly it's very subjective because one person's moderate might be another person's severe headache. But it looks at each of the five things headache, guts or stomach, basically Ms appetite and nausea, tiredness, dizziness or lightheadedness and difficulty sleeping. This is like Louise in Candida and up until the pandemic. There have been annual hypoxia symposia held at Lake Louise, where groups of altitude experts have got together and the original Lake Louise score was first, um, proposed at this venue. So the like Louise school was actually designed as a research tool, but it has been used as a clinical decision tool and the original definition was the presence of headache and at least one other in terms of dizziness, loss of appetite, fatigue and poor sleep. Another said. Each of these symptom groups is rated 0 to 3 none mild, moderate and severe. And if there's a headache and other symptoms, a score of three or more than this is AM s by research definition. Everyone sleeps badly when they go checking. If you've slept in mountain huts in the European Alps and other parts of the world, you'll know that there are many reasons why people don't sleep. And so in 2018 at one of these symposia at the Lake Louise Hotel, a large group of experts got together and felt that the Lake Louise score, as initially described in 93 should be modified and sleep should be removed. Four of the symptom groups remained headache, gastrointestinal symptoms, fatigue and dizziness. But sleep is removed completely, but they added the AMS Clinical functional score, and the question is overall, if you had a M s symptoms, how did they affect your activities? So none at all 01 symptoms present, but did not force any change in activity or itinerary to my symptoms forced me to stop the assent or to go down on my own power. Or three had to be evacuated to a lower altitude. I had done some work on adolescents trekking at low altitude, in fact, on Dartmoor in the UK, so clearly not at high altitude and looked at the false positive rate of AMs because the students weren't at high altitude and found quite high levels will come back to that. But these figures, uh, that I had had measured as part of my master's degree, um, I undertook a dissertation on altitude in teenagers. This data was re examined, and we put a paper out in high octave medicine biology a couple of years ago now, and this underlined the importance of removing sleep from the Lake Louise School. It's not difficult to work out why so many people have disturbed sleep. One of the effects of being at high altitude is that you get changes in your breathing. You get periodic breathing, and so most people wake often and not feel refreshed after a night's, uh, rest. But as you'll know, if you've been in that kind of environment, there are other people who are snoring. Sometimes it's cold and drafty doors banging in the wind, needing to get up for a wee being uncomfortable every time you turn over on the sort of waterproof mattress is there's lots of noise. Your neighbors are getting up at three o'clock in the morning so they can go and bag a peek. All of these things are going to disturb your sleep. Personally, I strongly recommend good quality earplugs and avoid caffeine and certainly avoid alcohol. Uh, when you're when you're in that kind of environment, so sleep is no longer considered part of the Lake Lory School. Okay, going back to the study that I published about 10 years ago now I was looking at, but ground rates of AMs like symptoms reported at low altitude in as a adolescent. So I had a cohort of 100 and 23 adolescents doing a three day trip on Dartmoor, and I asked each student morning and night to do a late Louise score and because, uh, I was there and I was able to see each group morning and night. I managed to get 100% response rate so each student filled in the paperwork morning and night. And it's the largest study to my knowledge, uh, in terms of the control at low altitude. But I found that about 8 to 10% of of students we're getting scores, which would suggest that they had AM s even though it couldn't have been because they were operating at low altitude. There are also other illnesses, which can give you similar symptoms, so migraine is provoked by being at Hiles dead, but it tends to be a different kind of headache. Most people will describe a classical migraine as 11 sided, whereas AMs headache tends to be more of a pressure all round. Worse if you cough or strain. Some people will be tired and have headaches with viral illnesses, but they often will have other upper respiratory infection symptoms, such as sore throat or runny nose and cough. Some people drink too much when they go on trekking trips and alcohol producers, dehydration and some people are clearly hungover. Following a heavy night. Diarrheal illnesses again can make people very tired, nauseated, sometimes vomit, and the last three illnesses are very important because clearly exhaustion, dehydration and hypothermia could be causes for your symptoms, but it does mean that looking at those last three, we can rapidly exclude those by resting people, giving them some fluid and warming them up. So that's important. When you consider treating Bruce, for example, who was our patient on Kilimanjaro, so certainly rest fluids and keep warm. What's happening with acute mountain sickness? Well, the exact mechanisms are not precisely clear, but there's definitely brain swelling from hypoxia induced phase of limitation. Remember that as your oxygen levels drop, the body compensates by dilating the blood vessels to the brain. So this is hypoxia induced vasodilatation, and you also get some cerebral edema, and it may be due to impaired cerebral auto regulation. So this hypoxia induced face deportation, which may be more or less prominent in some people. There's definitely a role for Visa genic mediators and changes in the blood vessel permeability. But we recognize that high altitude cerebral edema is just one end of the spectrum, which starts with acute mountain sickness. Perhaps some have a reduced hypoxic ventilator response, and there's also a theory that those who have a tight brain so at my age, I've got so much cerebral atrophy and cerebral spinal fluid, then that can quickly be shunted, Um, when I developed my cerebral edema when I go trekking. So this is the so called tight brain hypothesis. If you're interested, you may want to look at a key paper by Mark Wilson Um, and Chris Emre in The Lancet, published in 2009. And it's the cerebral effects of sent to high Altitude. Now it's a very, very busy slide, but I've summarized on the right hand side what the slide is showing to us. So we're going from left to right, moving from an artery to the vein, so hypoxia causes vasodilatation. And with the hypoxic ventilator response, there's reduced CO2, and there's a constriction. So it means as you breathe faster, you blow off more carbon dioxide. And maybe there's the development of cytotoxic edema from hypoxia induced surgeon potassium ATPase failure, and there's probably a role for free radicals which damage the vessel basement membranes. So H I f hypoxic ischemic factor one alpha and, uh, the e g F vascular endothelial growth factor may also then contribute to further damage. There may be local hypochelemia and that can trigger calcium mediated nitric oxide release and further vase of debilitation and dilatation of the vessels activates the trigeminal vascular system and causes headache rather like you see in migraine. And you may also see microhemorrhages. But this is what's thought to be what's happening with AM s and in more severe cases with cerebral edema. Let's leave physiology behind for a moment and go on to acclimatization and what actually happened. So the body adapts over time to lower levels of oxygen and having worked with many people in different parts of the world. At high altitude, you notice that different people adapt at different rates. But one of the key things is to go more slowly once you reach around 3000 m and there are different guidelines which suggest maybe 300 to 500 m per day and provide people go up slowly enough. Most people can acclimatize at this sort of rate, and when working with groups, we tend to say, walk high and sleep blow, and that means that it's your sleeping elevation, which is most important. So it's okay to go over a high pass and then come back down again to sleep, and most of the acclimatization guidelines suggest rest days. These aren't really rest days where you sit around and do nothing. These are days when you should stay two nights at the same altitude, and it goes back to what we looked at earlier is the ascent profile, and that can be very useful when trying to work out how quickly to go up a mountain. This is Kilimanjaro and the different routes up the mountain are shown. We talked about the meringue go route, the Coca Cola root, which goes up 1000 m a day, which clearly is outside most of the recommended guidelines. It's just too high, too fast. If you go up the Mitchum route, you tend to go more slowly over a longer period of time and you go across the mountain and then go up to the summit via the Creator rim. Some of the other routes, like the Shira and Lamu shoe route and wrong guy. They will come in over much longer periods of time, and therefore your chances of reaching the summit are higher. We looked at the meringue go route when we were talking about Bruce, so you starting off at 1800 m 1,409,700 then to the summit on the morning of the fourth day. So, not surprisingly, some studies have shown that as few as 50% of people will reach the summit if they go up the meringue. Go route. Ultimate Kilimanjaro is a good resource where you can find all of these ascent profiles and it shows the different roots up and down the mountain. So many people will camp and go up. The match arm route, which is, I said, tends to go up and across the mountain. Um, and they don't go back the same way. They drop down quickly via the Millennium camp and more waka. If we look at the match, um, route, you can see, um, the website is, in fact, an American one, and they use, uh, feet. But I've put the calculations that have changed. Um, the figures, 2 m. So I've shown the height gains, uh, at the bottom in meters. So 1209. 60 then 8 20 then a drop of 650 then very small height gain just 17 m, then 678 up to 1200 m. So the ascent profile is much more favorable and makes it more likely that patient's clients trackers will reach the summit. This is Everest from Kalamata, so just above the Everest base camp. So this is around 5545 m. And as I said earlier, the partial pressure of oxygen here is about 50% what it is at sea level. Uh, and if you reach the summit of Everest, it's around one third of what it is at sea level. But the ascent profile for a typical group trekking to over a space camp. And again, this is an area. But many of you may go to as your first high altitude track with with patient's or potential patient and you. What you'll see is that it's not as high as Kilimanjaro. But many people take up to 12 days to reach Garrick Shep and go up to calibrate our and back down again. So the incidence rate of, uh, severe AM s on Everest base camp, but trail is going to be a lot less. However, the distances involved between each of the villages is much greater and sometimes evacuation particular and helicopter evacuation isn't possible is much harder, whereas on Kilimanjaro it's quite easy to get down the mountain very quickly, looking at risk factors. If you've had a M s before then you probably twice as likely as other people to get a mess again. But in general, we can't predict just by looking at a group who's going to get a mess and who isn't. But certainly those who over exert themselves if they don't drink enough or if they're already struggling with an inter current illness is a bit like Bruce with his diarrheal illness or perhaps an upper respiratory infection. These make you more likely develop AM s. Certainly obesity and obstructive sleep up near our risk factors for developing AMs and more serious altitude related problems. I want to talk a little bit about taking Children too high altitude. Obviously, it's an opportunity for me to show off and show pictures of my kids when they were little. This is Tom at 5500 m with his class mascot. Uh, he was aged 11 and Sam reached over a space camp for the first time when he was just nine. Now, very young Children, I can't tell you how they feel. They may be more irritable or just go off their food. They don't sleep very well like everybody else, and they may just not be very interested to play. And it's probably just safest to assume that they've got altitude illness and go down. Obviously, older Children can describe the altitude symptoms, but don't rest under any illusions. I think taking very small Children too high altitude, in fact, on expeditions in general is largely for the benefit of the parents rather than for the child. So we need to think about very cautious ascent rates, and clearly we don't want to put them off going to high altitude and trekking in the mountains when they're very young, because we want to take them when they're a bit older. And other things like the lack of clean water, different food, needing to use sunscreen all the time, keeping them amused. You may be delighted to look at the mountains, but Children will very rapidly get bored with just looking around at at high altitude, um, beautiful places. So have very realistic tracking goals, particularly with younger Children. But that said, we got our kids out early. So this is Sam on the left hand side, um, age just around a year in the European Alps. But by the time he was nine and had had quite a lot of experience in the Alps, then he was very able to track all the way into Everest base camp. But I wouldn't have taken my kids too high altitude if they hadn't got a good pedigree of operating in high places and very confident on steep ground. So, you know, here, Tom is, is just six doing fear, Farrah to um. And then as they get older, they get more and more confident as they go as they go trekking just a couple of things about Children. Um, in general they have immature thermal regulation, and that means that they can get very cold very quickly. So you need to invest in good kit and be very aware when they go quiet, they may be getting more and more miserable and cold. They are certainly more at risk of developing pulmonary hypertension. They're quite often complain of ear pain, and they may be less able to equalize the pressures in that year. If they become unwell because of GI infections, they can become more seriously dehydrated than adults. And, of course, you need to be prepared to completely abandon your plans. It's important that you don't doggedly pursue your original plans despite the fact that you're young family is unwell. You might like to look at the consensus statement of the Union International Alpine East Associations Medical Commission, Uh, which was written in 2008. Uh, and that specifically looks at taking Children to high altitude. Right then. Well, we want to go to high altitude, and we don't want to get a M s. So let's look at how best to prevent AM s. It's all about gradual, flexible ascent and being able to walk and talk. However slow the walking might need to be is the best pace. This is so called guides pace. So you will work with a group and you'll realize that everybody stop talking. And that means that probably you're going to quickly, and people aren't enjoying themselves as much. So remember, guide space of being able to walk and talk. You can also prevent AM S by using medication so Diamox is used to prevent. And so also, uh, dexamethasone and ibuprofen. Interestingly, though fitness in itself doesn't mean you're not going to get a m s. And sometimes people who are very fit are used to becoming breathless, and they may put themselves more at risk by trying to go up the mountain too quickly. There are different recommended ascent rates and there was a review in 2014. And once you go above about 3000 m, the H r A, the Himalayan Rescue Association, recommend about 300 m a day with the rest for every additional 609 100 m, and no single day with the height gain greater than 800 m, whereas the W. M s the Wilderness Medical Society suggests 500 m per day with a a rest day. Remember, that means staying at the same sleeping elevation every three or four days, and these are the two recommended descent rates, but neither offers complete protection. Um, because different people were climatize a different rates. And as I pointed out to you when we looked at the meringue go and the Machar me roots. Uh, Kilimanjaro is a special case, and of course, you can't always stop 500 m higher because there may be no flat area. There may not be an area where there's running water, for example, so moderate exercise to prevent problems maintaining a good fluid intake. A high carbohydrate diet is helpful because, uh, carbohydrates produce 15% more energy for the same amount of oxygen when you compare to fat metabolism and alcohol and sedative drugs also don't help with acclimatization. We're going to talk more about acetazolamide or dialogues. Some of you may come across it as a drug for epilepsy. For glaucoma. It's also diuretic, but it's used and has been used for the prevention of altitude Dennis since 1965. It's a carbonic anhydrase inhibitor, and it helps to increase the oxygen content in arterial blood by stimulating breathing. It doesn't mask the symptoms of AMs. A lot of, uh, your clients or patient's will say to you, I don't want to take anything because it can mask a mess. It's not like taking morphine for a headache. Um, it just stimulates breathing and therefore hastens acclimatization. It's safe and it's effective and it's been used multiple times. Um, in the last 55 years, it does mean that the fatal complications, cerebral edema and pulmonary edema are less likely. In terms of AM s, the number needed to treat is only six. For those, um, who are going up with a sensible ascent profile if you're going more than 500 m per day, taking Diamox means that the number needed to treat is only four. And in another study, about 48% relative risk reduction versus placebo when taking 250 mg a day. Those people who are allergic to sulfa undermines shouldn't take Diamox because you can get nasty allergic reactions you probably remember from chemistry. TCS see days old level in my time that if you bubble carbon dioxide into water you produce. You get carbonic acid and the carbonic acid dissociates into bicarbonate teens and hydrogen ions. And with carbonic and hydrates, you excrete more bicarbonate earns in the kidney, which means that you retain more hydrogen irons. In circulation, you get a relative acidemia and relative acidemia. You breathe more quickly, and that's how Diamox works. Moving on to treatment of AMs having having discussed prevention and clearly one of the best ways to prevent it is not go any higher. Remember, I talked a little bit about dehydration, exhaustion, hypothermia and low blood sugars as potential courses for symptoms. So if you rest, people give them some fluids, some calories and warm them up, Then many people will feel better. It's safe to give simple analgesia, paracetamol or ibuprofen. I personally use prochlorperazine or stem A till the anti sickness drug, which I find very useful. Um, I don't like using metoclopramide, particularly in young adults, because of Estonia's tax on methadone can be used for treatment of AMs Um, and some people use Diamox for treatment if it hasn't been used in prevention, and there's little evidence for its effectiveness in treatment. Um, but there's tons of evidence for its use in prevention. And clearly if people don't get better with simple treatment than we should consider descent, and often just a few 100 m can make quite a big difference. Everybody who takes Diamox get side effects. You get tingling in your fingers and your toes, sometimes in the ears or the tip of your, um, tip of your nose. And, uh, this is particularly when you get cold hands, uh, taking your tents down in the morning. It's a diuretic, It's mild diuretic, and many people will have quite a mark Dyer ASIS in the first couple of days when they're taking Diamox and carbonated drinks. Taste distinctly odd. Um, so the beer that you've been looking forward to won't take won't taste anything like would have put at sea level if you weren't taking Diamox. So the studies indicate that those we should use is 100 and 25 mg twice a day above 3000 m. Or in my experience, I've been using one tablet of 250 mg once a day in the morning. And that means that you get your diuretic effect out of the way early on. If you're going to take Diamox for prevention, then start at around 3000 m and then take it until the highest point of your track and then stop. And it could be restarted if symptoms redeveloped and for treatment of AMs. The recommended dose is one tablet twice a day, and then you continue until you until your symptoms settle or you get further medical advice. A few years ago, one of the diploma students, uh, and I put together a paper with another colleague on altitude sickness and acetazolamide and put together a 10 minute consultation published in the BMJ for, um for GPS who may be asked to advise their patients' about going to high altitude. There's some useful information on the study on the effectiveness of of Diamox for you to refer to, If you wish now one of the most important pieces of literature that you need to be aware of the W. M s guidelines. These are updated every few years. The latest guidelines was issued towards the end of 2019, and I'm going to summarize what we've been talking about to date by initially looking at the W. M s practice guidelines on prevention so very quickly. If you read through the guidelines and I'm going to summarize them here, they say, after you'd illnesses occur above 2500 m, that's AMS, hastened hape. But they also point out that severe dehydration, pneumonia hypoglycemia can present with similar symptoms. They also say that hace is an extreme form of AMS and prevention and treatment for both can therefore be considered together. So to prevent AMs and hace. It's all about gradual ascent, and they suggest sleeping elevation is considered more important and above 3000 m. Restrict your height gain to less than 500 m per day, with a rest day every three or four days. But these ascent rates can be averaged to allow for availability of suitable campsite and so forth. And in terms of prevention, they point out that the deceit is all in my Diamox. Um, there are multiple trials which have established the role of acetazolamide and prevention, and the recommended dose for adults is, as I said, half a tablet, 100 25 mg twice a day. There has been a small study with an even smaller dose. 60.5 mg cells a quarter of a tablet twice a day, but certainly higher doses are associated with increased side effects and are not recommended. They say that dexamethasone the steroid can be used for prevention at a dose of 2 mg four times a day, but shouldn't be used for more than 10 days. And, of course, steroids are not without risk. And they definitely shouldn't be used for prevention in Children. In terms of, um, am S and hace inhaled budesonide is not recommended. Jink a biloba. Some trials have shown a benefit of those haven't and ibuprofen and paracetamol. So 600 mg of ibuprofen three times a day is more effective than placebo in a couple of trials, Um, paracetamol intensive prevention of ams and hes Um, again, this hasn't been, um, isn't recommended. There's only weak data that it helps to prevent. There's also a bit in the paper about prevention of AMs and hace with pre acclimatization and staged ascent. So if you spend about a week at 2200 to 3000 m, that's going to reduce your risk of developing altitude in like a m s and hes. But you may have heard of people who go to these hypoxic chambers. And short term exposure is unlikely to be of any use, but more than eight hours a day for perhaps a week or so, maybe of some benefit. So you may have heard about, um or maybe ask questions about somebody wanting to go off the exposed to a high hypoxic environment to encourage their acclimatization. You may also get asked about the use of coca leaves aspirins from the lactose on sumatriptan. But there's no current evidence to support their use when to use drugs like Diamox for prevention of AMS and hace Well, they suggest that prophylaxis is advised for those in moderate to high risk situations. So moderate risk will be a prior history of AMS or going more than 500 m per day, or high risk AM s and haste before and ascending to 3500 m in a day or with very rapid a sense. And that includes Kilimanjaro. For the reasons that we've already discussed the W a mass guidelines are pretty clear. They say Diamox is the preferred medication. Um, they also feel that there's low cross reactivity with other sulfonamides, so it may be advantageous for patient's clients to take Diamox before departure. Um, I have had a few patients who've had difficulties with sulfonamides in the past. We used to use Septrin in Children for year infections when I was young GP, um, I've certainly seen some quite persistent Stevens Johnson's rashes. So, um, it's not to be taken to, um uh to mildly because it it can take a week or so to settle. The W. M s guidelines also suggest that you start the day before sent, and you then discontinue when you reach your high point. I was lucky enough to be paid to go out and climb Kilimanjaro as a risk assessment for World Challenge some years ago. And this is the, uh, the view at the top. Uh, you're a peek At 5895 m. I was taken by the view of of some people being almost carried to the summit by the local local porters who were vomiting and headachy and so forth. Um, and it just underlines the fact that many people who developed AM S and hes uh, and and prominent Lima to has seen on Kilimanjaro. But I'm going to focus on high altitude cerebral edema. The brain clearly needs a good supply of oxygen. And as we talked about earlier, low oxygen levels can lead to brain swelling, and it can be rapidly fatal if it's not treated and of the altitude effects on the brain, then hastens the most important problem. I pointed out that migraine, um, is provoked by going too high altitude. Some people get mood changes, and it is even possible to have a stroke. I have seen a teacher, in fact, with a group on, uh, on two Morava in Ecuador who had an occipital event, Um, and ended up going blind temporarily, um, at the summit. Remember, I talked about this, uh, seminal paper, which was published in The Lancet in 2009. It's a It's a busy slide, but I've blown up the left hand side of the of the slide a bit on the right. Um, what this shows is that as you go to increasingly high altitude, you get more and more, um, cerebral effects. So at high altitude, you your, um, complex reaction time slows, there's psychomotor impairment. And then as you go to very high altitude, you get learning and spatial memory impairment. And then above 6000 m, memory retrieval is impaired. There are MRI changes, and astonishingly, around a third of climbers have hallucinations above 7500 m. So it's worth bearing in mind. Um, these neurological consequences of going to increasingly high altitudes, how common is hace well. The incidence is around 1 to 2% at 4.5 1000 m. I mean, it usually comes on above 2.5 1000 patient's will have probably had symptoms of AMs and then gradually the symptoms will worsen on the second day. The headache is significantly worse than you'd get with acute mountain sickness. Now, nausea and vomiting are more pronounced. People are confused, can have hallucinations. And certainly, in my experience, I've seen clients becoming clumsy. They get the so called grumbles, mumbles, stumbles and then tumbles. They're often exhausted. They can get blurred vision, and quite rapidly they can lapse into a coma. Because hypoxia is the main problem, You can also get high altitude farming odoema, even though it has a different path of physiological, uh, mechanism. And I'll go on to explain that. So we would look to assess somebody who's possibly got cerebral edema by looking at the pulse rate, their breathing rate, the Romberg test. Remember, when you ask someone to stand, whether arms folded and they close their eyes so very often they've lost their appropriate reception and begin to fall over. But the main test you need to be aware of is heel toe walking in a Straight line, which incorporates 100 and 80 degree turn and also made the simple mathematics doing cereal servants back from 100 if there's impairment of any of the above. So they've got abnormal pulse, a breathing rate, abnormal Romberg, etcetera and suspect high altitude cerebral edema. If we think someone may have early cerebral edema, they shouldn't be left alone. They should be set up if oxygen is available. Clearly, that helps to reverse the hypoxia. Consider a portable altitude chamber and then the emergency medical treatment Medically with drugs is text Metha zone 8 mg initially than 4 mg. Q. D s Diamox can be used for treatment, but it's much less effective and also takes quite a long time to work. So the key thing is to go down and don't come back up again. If Sarah blood ocma is untreated than the confusion and drowsiness worsens, the patient will lapse into consciousness and, um, become more and more deeply comma toast and you get classical signs of increasing, uh, BP dropping pulse rate, reduced breathing, koning and then death. So drugs and dissent prevent death moving on to high altitude pulmonary Dema. Then, as we know, the barometric pressure is lower and there's a reduced pastor pressure, oxygen, and so breathing is faster to compensate, and many people who go to high altitude, uh, will have a dry cough. But what we're most worried about is the development of high altitude pulmonary edema. Having trekked many times in Nepal, you'll often hear people coughing and spluttering with quite rattly coughs. This is the so called cumbia cough from the the Khumbu Valley Um, which isn't a direct effect of high altitude, but it's the presence of, uh, of lots of respiratory pathogens in the area. Hape comes on two or three days after arrival at high altitude, and one of the first things you'll see is big changes in exercise, tolerance and marked tiredness. And most prominent Lima worsens the breathlessness at rest becomes a feature with breathing rates greater than 25 to 30 breaths per minute as a cough. And in the very late stages, as you might see with other causes of promenading that you can see frothy, bubbly sputum. There's sometimes central and peripheral cyanosis, and there can even be a mild fever up to about 38 degrees, which can make people think of infection. And again, the incidence rate is around 2% at 4000 m. If we look at some X rays of what happens with pulmonary edema, you get this classical batwing appearance of the fluid in the lungs. On the left hand side, you've got a patient, um, three and five hours after treatment. So quite rapidly, um, you get resolution with the with the right treatment. But this is not a situation where we would use a furosemide different mechanism from patient's with congestive cardiac failure. So the treatment of hae health Deep pulmonary edema again, as with hate, don't leave them alone, set them up, keep them warm oxygen and again the particularity chamber. But now the medication is nifedipine, which helps to open up the pulmonary arteries and reduce the, um, the pulmonary artery pressure, uh, and then follow that up with 20 mg every six hours. Again, Diamox less evidence. But that can help. Salbutamol may also help with the re absorption of fluid from the alveoli and again descent and do not re ascend. But, sadly, patient's can die very rapidly from high altitude pulmonary edema. You may get a chance to have a look at a portable altitude chamber, so it's basically a pressure bag. It's that easy. These are my kids showing a group of doctors how to use it. And if you put someone inside the bag and you pump it up with a foot pump, then you can achieve pressures of 2 lbs per square inch inside the inside the bag. And this can lead to rapid resolution of symptoms. As I say, hate is a non cardiogenic pulmonary edema, and it's thought to be due to exaggerated pulmonary hypertension in areas throughout the lung field. So it's it's not uniform to get patchy changes, and you get vascular leakage through over profusion. And there's stress failure of capillaries. So it's definitely seen in patches. Um, there's thought to be dysfunction of the endothelial in the blood cells, uh, sorry. In the blood vessels mediated by nitric oxide, there's also roles for, um, inflammatory proteins and also reduced al viola fluid clearance going back to the W. M s guidelines. In terms of treatment, they say four AM S and hace, then descent is the single best treatment, no surprise there, and symptoms usually resolve with very small dissents of 302,000 m of dissent. And if you use supplemental oxygen, that will help to reverse the hypoxia. So the aim is to maintain saturations above 90%. There's good evidence for the benefit of hyperbaric chambers, and they're very effective. But remember, patient's who are vomiting, Who's airway may be at risk or, if they're very claustrophobic, that can be very difficult to manage. Symptoms can recur after you've increased the pressure, the ambient pressure but putting them inside a portable altitude chamber safe to use parasites more like the profin. There's some interest in the use of See Path. Um, at the moment it can't be advocated. There are definitely more studies needed, but it would be a probable way of treating uh, certainly pulmonary edema acetazolamide in terms of treatment again, you know, one tablet twice a day. But a small number of studies dexamethasone is certainly very effective, and there's extensive clinical experience of the use of of dexamethasone for the treatment of cerebral edema. But these are very large doses. You're talking about 8 mg and 4 mg q. D s. That's the kind of dose we'd use for somebody with a brain tumor just talking about the W. M s guidelines and pulmonary edema. They say that some of the prevention and treatment modalities are the same as you would get for AMs and hes. But as I pointed out, Hape has a different path of physiology and therefore different management in terms of hate prevention. There's a clear relationship between the rate of ascent and the incidents of Hape lots and lots of people who are so called HAPE susceptible. So the people who get Hape every time they go to high altitude have been shown to benefit from nifedipine. The extended release form 30 mg twice a day, and they start that the day before and until they go back down again. There's a single trial in the beta agonist salmeterol, and that decreased the incidence by by 50% at a dose of 100 and 25 micrograms twice a day. But that's only a small trial again. There was a small trial on $2 a pill because of its effect on the pulmonary artery, and it is thought to be effective in preventing HAPE. Dexamethasone has limited clinical experience, but it reduced the House Department edema, and there's also a role for inflammatory protein, so it's logical to use dexamethasone. But one of the key things that came out of the latest guidelines is that acetazolamide should be affected at preventing all forms of altitude illness, and there are no trials in hate prevention. But they say it is a rational choice. So, as you can probably tell, I'm quite a big proponent for the use of Diamox. I consider that Diamox, uh, is in the same sort of category as antimalarials and immunizations because we have something which we know works, which helps to reduce the incidents and therefore will challenge groups have been using Diamox for prevention of altitude analysts since 1993. Um, so I probably, uh, prescribed 100,000 doses in that time. Extraordinary number. Uh, you know, we turn perhaps, um, 5000 kids away every every year, and it's now 30 years since I've been advising them. So we've you. We have a large degree of experience using, um, Diamox prevention of altitude illness. The W. M s guidelines say go down? Yep. Um, trying to avoid existence or better to carry them down rather than to walk themselves down oxygen again. Maintain saturations above 90% portable. Uh, altitude chambers are effective. But again, Ortho paneer is a problem when you've got any breathing problem. So if you have somebody with pulmonary team and they're not going to want to lie down, so you may need to prop the chamber up lots of experience of using, um nifedipine, and they suggest using 30 mg extended release twice a day. I'm always a bit cautious and tend to use 10 mg, initially followed by 20 mg. Um and that's because if you are already unwell with low BP, you may lose your BP completely, but they suggest 30 mg extended release twice a day. There have been some case reports on the use of beta agonists. Uh, certainly I've got some anecdotal evidence on the value of salbutamol for a patient with, uh with Bowman edema, and we know that Viagra talk to other fields are done. I feel that type of drug, they decrease the pulmonary artery pressure, but don't use diuretic. The same reason I wouldn't use high doses of nifedipine because you tend to lose, uh, BP further in those who are already very unwell. So particularly furosemide. End of the loop. Diuretics, uh, may cause profound changes in blood pressure. And as I pointed out, dexamethasone effects pulmonary inflammation and therefore may have a role in treatment. So now you know a bit about the pathophysiology of high institute illnesses. We've been doing a bit of a mechanic. Um, work. Now, let's look at being more of a car driver. So you're working with a group at high altitude as here in, um in the region just before Everest base camp. If we can score, uh, patient's symptoms, then we may be able to provide guidance on their management. So remember, in 2018, they modified the Lake Louise score, and we now look at only headache, gastrointestinal symptoms, fatigue and dizziness together with the AMS Clinical Function School. But once you've scored your patient, who is unwell, we can then look at how we might manage them. So if they have a score of less than three, then they don't have m s. By definition, if they have a score between three and five. This is mild AMs But if you're getting a score of six or more, then we should do two things. We should test their coordination and the conscious level and their breathing rate. So we do here to walking. Measure the breaths per minute, and if there's no loss of coordination, no reduced consciousness, then this is moderate AM S. But if they've got loss of coordination, changes in conscious level or they've got a fast resting respiratory rate of greater than 25 breaths per minute, then this is severe altitude earnest. Either AM S Hayes or AMs hate. So this can be a useful clinical decision tool. Remember, it was never designed to be a clinical decision tool. If one of you can come up with a better scheme, then that would be great. But at the moment, the only thing we have is the 2018 night Louise School. So some companies will use the low calorie score, too. Guide treatment. So with the mild AMs score, patient should be treated with rest and fluids. Paracetamol, maybe Diamox. Maybe something for sickness like stem a till, and if symptoms improve, then it may be possible to cautiously go on. But if they've got moderate AMS with a score of six or more, then they know that they need to test heel toe walking and look at the breathing rate per minute, obviously the conscious level as well and again same treatment. And if they improve, then they may be able to, uh, continue to ascend. But if they don't improve, then they need to go down. But if they've got symptoms of severe acute mountain sickness with poor coordination, fast breathing rate or changes in their conscious level, including need to stop and go down and give dexamethasone, and if they've got fast breathing, they should have nifedipine, possibly salbutamol. I need to be set up and kept warm, certainly oxygen. If you've got it and the portable altitude chamber and then compete. Continue treatment until reaching medical care. And don't forget if you helicopter evacuate somebody down to Kathmandu, they may need a couple of days in hospital before they fully recover, and they sometimes end up with persistent changes in the uh, coordination for quite a while after they've had, uh, cerebral edema, for example. So let's do a little example together. Let's say you tracking in, uh, North Africa, that 40 year old tracker, moderate headache, nausea, severe fatigue and they're not dizzy. So if you think about the score ng, that's gonna be two for headache, say one for nausea, severe fatigues of three and not dizzy. So zero total score is six. So that means they need to have further assessment. So we would look at heel toe walking, and in this case, it's normal. They're fully conscious and obviously able to cooperate with your requests, and the breathing rate is only 20 per minute after rest. So what sort of treatment do they need? Well, this is her name. Moderate AMs isn't it? So we would go back to giving them fluids, paracetamol, maybe something for sickness and close observation. Just look at the portable altitude chamber for a minute. We know that they relieve symptoms. It's certainly more effective in treatment than acetazolamide or Diamox. But what's important is that it can buy valuable time, and it may enable a walk in casualty. As I say, you inflate the altitude chamber 22 lbs per square inch. And if you look at the graph, which is actually on the side of the PA see Australian version. So at 5000 m, a 2 lbs per square inch, that's equivalent to dropping them down to 3250 m in terms of use of the portable altitude chamber shouldn't be used if the patient is unable to protect their own airway, and really the best treatment is descent. But if you've got a delay or it's not safe to move down during the night, for example, then the portable altitude chamber may be very valuable, so some teams carry them with them. You'll find that they're dotted around in high altitude areas throughout the world, so explain what you're going to do. Put them into the chamber and establish an emergency signal in case they feel they need to get out. They quite common to get ear ache, and it's important to talk to them about equalizing middle ear pressures and then place a bag on a flat surface. You may prop up the head end, but make sure that the portable altitude chamber is anchored to the mountains so it doesn't go sliding off down the snow and then put the patient in a sleeping bag or something to keep them warm. And, if possible, it's useful to put a pulse oximeter on the finger and aimed for saturations above 94%. You can put oxygen inside the the bag as well, and then pull the zipper closed and begin inflation with the foot pump, and then you inflate to PS I. There's a little blow off valve so the flat will, uh, lift and you'll know that you've reached a steady state at 2 lbs per square inch, and you need to put fresh air into the bag because you get accumulation of carbon dioxide's. You need to put fresh air in by pumping, Um, every four seconds, you need to put a new a new pump of air in, keep a close eye on them and then gently deflect the bag every hour or so to reassess. It is possible to get chemical oxygen, and that has been used in certain circumstances. So I first came across this on Kilimanjaro, I said to my guide, you know, where's the nearest oxygen? He said, I've got some in my bag, and this is a South African product. It has a carbonate and manganese dioxide, and you basically just add water and you get 100% chemical oxygen and you can get rates of about two liters per minute from from that combination, It rather depends on the the temperature of the of the water. Um, but this again has been used in anger, and it obviates the difficulties that you'd have in, uh, trying to transport pressurized cylinders of oxygen, which are very difficult when you're flying. So, um, that's something that you might want to think about that is available in the in the UK from people like SP Services. You'll see clients, guides, people using pulse oximeter is when you go to high altitude. I think sometimes too much reliance is placed on them. They're certainly simple and cheap, and they estimate the amount of oxygen that the blood is carrying. But they don't predict or diagnose AM s. They can only be used as an adjunct to your judgment and the whole clinical picture. The only thing that they may identify is those with incipient pulmonary edema. And I think what we're really looking for is somebody who's got much lower saturation than everybody else in the group Because, as you are higher, we look at the graphs earlier. We know that the oxygen saturations are going to drop as the partial pressure of oxygen reduces. So really, we know, because we know that the oxygen levels are going to go down. Um, as you go higher. Then the only really useful thing is to see party members who have a lower, considerably lower oxygen saturation than others. And we need to watch them like a hawk. Um, but even so you know, I've had oxygen saturations of of 70 and felt absolutely fine. You know, that would win me a place on i t. You certainly wouldn't It, but felt absolutely fine, uh, with that kind of, um, saturation. So it doesn't necessarily give you very useful information, but that said, I will certainly carry a pulse oximeter with me coming to the end now and going back to where we started. So remember we had Bruce on Kilimanjaro. He had tracked up from the meringue a gate to Mandera and Ha Rahmbo. Remember, this is going up 1000 m a day. Um, and he was unwell and was very slow getting to cube Oh, So the question I gave you earlier on to think about it was, you know, it's 4. 30 in the afternoon, with perhaps a maximum of two hours of daylight to go. Bruce has got a moderate headache. He throws up a couple of times. Um, he feels lightheaded, and he's moderately tired and wants to go to sleep. So now, because we know about AMS score ng We can score Bruce. So he gets to for headache to for vomiting, one for lightheaded and moderately tired. So he's got an AMS score of seven. So what do we need to do? Well, we know that we need to check his heel toe walking, which is okay. His resting respiratory is only 20. He's alert on the scale. So is this moderate or severe a mess? Well, clearly, he has only moderate ams because he doesn't have signs and symptoms of cerebral edema or pulmonary edema. So what do you do? Well, he doesn't go to bed because we want to keep an eye on him. We give him some fluids, we give him some paracetamol, perhaps some buckets stem. That's the buckle formulation of prochlorperazine. And he starts in dialogues one tablet twice a day, and a couple of hours later he's feeling much better and he wants to have some soup. So as the medic with a group where you can say, Well, you know, you've got probably 67 hours to rest because, well, normally, get up at one in the morning to try and get up to the summit. You can say, Well, you can try in the morning, But the reality is he's not very likely to get to the top. So he'd be much better off resting for one day at Kibo or even going to more Wenzy Peak, which is 5100 m and coming back. That would be a far better way of optimizing his chances of reaching the summit. But if Bruce wasn't any better, so he had moderate AMs but not getting better. Then he may need to go down with an assistant guide. He needs to be kept warm, need to carry on with his treatment. Let's look at another example, uh, on the Everest base camp trail, got a 48 year old client who's got an M s score of nine. But in this case got very poor heel toe walking and very drowsy. So in the photograph, you can see the need to be accompanied by a local porter because they're very, um, poorly coordinated. So this is now severe. AM s with several edema. So the treatment in this case was stop, go down and dexamethasone. And if they developed respiratory symptoms so rapid breathing at rest, then I've had have been possibly so beautiful. Sit them up. Keep them warm oxygen, portable altitude chamber. And I need to continue treatment until they reach medical camp. So open the last hour and a half or so we've looked at the path of physiology we looked at score ing am s. We've looked at the W. M s latest guidelines for treatment and prevention. I think we'll have a chance to talk more about how else did when we meet. Um, but in the meantime, I hope this has been useful. And thank you very much for listening. Yeah,