I had the opportunity to attend and present the Craterhab Technology at the 9th Chronic Hypoxia Symposium and the 1st High Altitude Space Physiology Symposium at the High Altitude Pulmonary and Pathology Institute, La Paz, Bolivia (24 Feb to 1st Mar 2025)
Craterhab Technology is the signature product of Mareekh Dynamics, and deals with large-scale habitation solutions for low pressure planetary environments such as Mars and the Moon, and the high-altitude terrestrial environments on Earth such as high-altitude cities, mining sites and research bases. While in the planetary environments, its core purpose is mere sustenance of human beings in the vacuum or near-vacuum environment, on Earth, it is aimed at mitigating the short and long-term damaging effects of hypoxic high-altitude environments with thin atmospheres lacking oxygen. These altitudes range anywhere from 3000m above sea level to up to 5000m or even beyond where the atmospheric pressure can be down to half of what is at the sea level.
La Paz, the capital of Bolivia, and its adjacent city of El Alto are situated at 3500 and 4100m above sea level respectively, together forming the highest substantial human settlement on the planet. With a combined population of over 2 million individuals, it is truly called the hypoxia capital of the world, where a significant fraction of the population lives at the risk of chronic mountain sickness; an inevitable outcome of the prolonged exposure and adaptation to the low atmospheric pressure and poor oxygen.
I have worked on hypoxia and its effect on the human body and its mitigation with our Craterhab Technology, originally developed for the space and planetary environments, for over the last two years. I have gathered insights, scientific data and statistics from countless articles and resources about the high-altitude human physiology and the effects of altitude hypoxia on the human body. So far the knowledge had been purely theoretical, since I was born and brought up, and have spent pretty much my entire life at sea or near-sea level altitudes.
As Morpheus told Neo in the movie The Matrix (1999) that unfortunately no-one can be told what the Matrix is…you have to see it for yourself. The same is very true for the high-altitude hypoxia. So I decided to follow the white rabbit.
Day 1; Landing at El Alto and the Hypoxic ‘Shock’
The Latam flight from Australia to La Paz (with connections at Santiago and Lima) landed at the El Alto International Airport at 4:25am on 24 Feb 2025; the first day of the symposium.
Contrary to my previous belief that perhaps the altitude sickness was a bit over-rated, I felt it immediately the moment I stepped out of the plane onto the jet bridge…the unmistakable feeling of not getting enough oxygen even with deep breaths. It hits you pretty much straight away, especially when you are an unacclimatized individual who has always lived at sea level altitude (I call any altitude below 500m as sea level). And it does not get any better from there either. It then hits you hard. Surprisingly, it did not cause any shortness of breath; just an uncomfortable feeling of doom. Being curious, I took out my pulse oximeter, which I had kept in my hand-carry precisely for this very purpose.
80%! I was in disbelief. I kept it on for a few minutes with a hope that it may be the initial low reading. In the next few minutes, the only change that happened was it dipped into the 70s transiently and kept bouncing back up to 80% with brief readings of 81%, and that was all.
This is what it is like to breathe at 4150m altitude in a 0.6 bar atmospheric pressure (or 60% of what one is used to at sea level and with a haematocrit of average 40%). To make it worse, I was yet to go through the immigrations and customs, fill out online declarations and a few other things and navigate my way through with full presence of mind in a non-English speaking country.
Finally, I was found by the kind taxi driver, Miguel, especially delegated by Dr Gustavo of the Altitude Clinic (HAPPI-IPPA) and the organizer of the symposium. My best hope was to get to La Paz central business district 600m below in the valley at 3500m as quickly as possible.
It was a swift ride to the Hotel NC La Paz which is roughly 10 minutes walk from the Altitude Clinic.
While the depth and rate of breathing settled as I got a chance to take a shower and stretch my back and legs briefly, the oxygen saturation came up to 84% which was a huge relief for me.
Shortly afterwards, Bruce from the Altitude Clinic was at the reception to guide the walk down to the clinic for the symposium. It is a short stroll crossing a couple of streets and a lift to help navigate the 60m descent from the hotel level to the clinic level in the generously contoured city of La Paz.
Walking level-ground was perhaps ok, but the worst was a staircase of nearly 40 steps to get to the Altitude Clinic from the cable car station lift. An unacclimatized individual like myself cannot simply climb this flight of stairs in one go. I had to break the ascent into 10 steps at a time followed by 20-30 slow deep breaths for recovery. Though I was feeling fine at rest, walking and going upstairs pushes the physiology to the limit at 3500m for an unacclimatized individual.
The ‘Ondine’s’ Curse
The first night in La Paz threw a curse at me. While I felt recovered to the baseline, the night had a sinister trick up its sleeve.
Right after I fell asleep, I woke up with a gasp, followed by rapid breathing and an uncanny feeling of doom. Presuming it to be all the tiredness from the journey, I tried to sleep again. The same happened over and over again every single time I fell asleep. I realized that I would stop breathing completely as soon as I fall asleep. Curious, I wore the pulse oximeter on the finger to check what oxygen saturation I was waking up with.
With the next waking up and gasping, I checked my oxygen saturation. It was 67%! (It is when I should have considered seeking medical assistance immediately.)
I realized that I was suffering from central sleep apnoea, likely due to all the rapid and deep breathing I had been doing involuntarily which had flushed out much of the carbon dioxide from my blood, and caused respiratory alkalosis. CO2 is an extremely important driver for spontaneous involuntary breathing and stimulates the breathing centres of the brain to do so. When we stop breathing, the CO2 produced in the body due to the metabolic processes builds up, triggering the respiratory centres in the brain to jump-start the spontaneous breathing.
My concern was that how low an oxygen saturation must go down to for the respiratory centres in the brain to kickstart the breathing. And most importantly, how reliable is this trigger? and what if it fails?
After realizing this, I started taking the Acetazolamide tablets which I should have commenced at least two days prior to the trip to La Paz. Acetazolamide helps breathing by stimulating the respiratory centres in the brain.
Though this periodic breathing or central sleep apnoea is not the same as the central hypoventilation syndrome (or Ondine’s Curse) which can kill an individual when one falls asleep, it is still quite analogous in its mechanism, except in the central sleep apnoea due to altitude, the CO2 build-up will spontaneously restore breathing within a few seconds.
Taking no chances, I decided to stay awake in the chair all night, making it the third night in a row with no sleep.
Day 2; Trip to Lake Titicaca via El Alto
Next morning we gathered at the cable car station to hop a ride to El Alto, back to 4100m, from where we were to catch a designated tour bus to Lake Titicaca for the day 2 of the symposium. Lake Titicaca, at 3800m above sea level, is the highest navigable lake in the world. This lake is so vast that the land-locked country Bolivia maintains a small Navy to administer the lake and its affairs. I was excited as well as sceptical if I had acclimatized enough in a little over 24 hours in La Paz to cope with the altitude sickness I had at the El Alto Airport upon arrival.
Upon reaching El Alto, there was a short half-kilometer walk from the cable car station to the bus. El Alto is very flat, and I didn’t have to navigate any upward or downward terrain which came in handy, and I realized I was performing well. At a roadside stall, I found a local selling some souvenirs. I purchased a small set of Andean panpipes that was decorated with local carvings and colours. As I tried to blow in it, I felt like blacking out, so I had to stop. The acclimatization I had achieved was merely for the baseline activities to barely breathe and live, and nothing more. So, excuse me…no coco loco boom, not just yet!...take it easy and just breath-in and breath-out, that's it. It was disappointing, but also helped me understand the dynamics of short-term acclimatization.
It was amazing to see Lake Titicaca for real, in its full glory on a bright sunny day, straight out of the Encarta Atlas of my childhood.
After the lunch, there were a few virtual lectures as part of the symposium at the Bolivian Navy Headquarters, which I attended while being almost half brain-dead.
Day 3; A standard symposium day at the Altitude Clinic
Nothing changed on day 3, except perhaps the acetazolamide had kicked in and I was able to catch up with some sleep the night before. So I stayed in character and participated reasonably well in the symposium. Few lectures were about the central sleep apnoea and the periodic breathing, and ways to mitigate it, which if I had known earlier, it could allay some fears that I had while having the same on my first night in La Paz.
Day 4; A drive down to Coroico, a tropical paradise
It was a part of the symposium program, and was a good opportunity to see the land transition from Alpine tundra at 4500m altitude, to the outskirts of the tropical rainforest, within a couple of hours road journey downwards.
Coroico is located at an altitude of 1700m; some 800m below the threshold of 2500m for experiencing altitude sickness. It is generally accepted that altitude sickness does not occur below 2500m, and this is one of the reasons for maintaining the cabin pressure of the passenger planes at cruising altitude matching the atmospheric pressure at this altitude.
I felt completely fine at that altitude, including the climb of over 150 steps to the town centre from the resort which I was able to do without much hassle, and with a short recovery time.
The visit to Coroico was a good proof of concept of rapid recovery from altitude sickness when one descends to lower altitudes. This is also the principle behind our Craterhab technology of pressurized domes simulating pressures of lower altitudes of 2000-2500m to help immediately recover from the altitude sickness without the loss of acclimatization.
Day 5: 1st High-Altitude Space Physiology Symposium
It was my day in La Paz, as this is why I was here in the first place. Thanks to Dr Gustavo for Scheduling my talk on Day 5 of the symposium as I was not in a good shape to deliver a talk on any prior days.
The talk went well, though I do remember nearly blacking out on a couple of occasions during my talk, where I had some incoherence in the speech for a few seconds and I had to struggle to stay in character and not create a scene. I think I did well.
Day 6; Trip to Oruro and the carnival
Oruro is a major town in Bolivia and is an important cultural centre, located at 3800m altitude some 4 hours bus journey from La Paz. My main excitement about this day was a chance to see the Bolivian Altiplano on my way.
The carnival lasts for two days and the segments of the entire Bolivian demography can be sampled here, in their full colours and cultural reflection.
Day 7; Return flight from El Alto
I was keen to see what oxygen saturation I would get at the departure from El Alto at the same time of the day as my arrival at the airport 6 days earlier. My guess was around 90%, which was fair. Saturating at 89%, I felt completely normal while sitting or walking around; a huge contrast to the eerie feeling of doom on arrival a few days ago. As I was fairly early at the airport and the flight to Lima was in two hours at 6am, I found myself a comfortable seat and dozed off. Until I woke up with a gasp…a similar situation I was in on my first night in La Paz at 3500m six days ago. It was an important moment of realization that the interval required to achieve short-term acclimatization is different for different altitudes. El Alto being 600m higher than La Paz, the acclimatization that I had achieved for La Paz was not quite sufficient for El Alto yet.
Take home message
Visit to La Paz helped settle a few misconceptions I had earlier about the altitude hypoxia by personally experiencing it.
1. I thought I would feel short of breath. But I didn't. It is more of an interplay between the brain and the hypoxic atmosphere rather than the lung and the atmosphere.
2. I thought I would struggle with breathing. Rather, I had rapid, deep, and effortless breathing even at rest (possibly due to acetazolamide). Any increase in activity only led to the feeling of zoning or blacking out.
3. I earlier thought it would take me some time to feel it. But it hit me hard pretty much straight away as I came out of the plane in El Alto. It was an unmistakable feeling of not getting enough oxygen rather than not getting enough air.
4. I understood the meaning of periodic breathing and central apnoea for the very first time, despite having a truck load of prior theoretical knowledge.
Some Suggestions for prospective visitors to La Paz
(These are based on my personal experience and may be unsuitable for some individuals based on their specific circumstances and background. It is always wise to consult your doctor for advice regarding travel to high altitude regions. )
Arrive a couple of days in advance. Allow your body to get used to the new altitude and pressure,
Take plenty of rest
Drink plenty of water
Start acetazolamide at least 2 days prior to arrival in El Alto after speaking to your doctor, if you are from sea level and unacclimatized.
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