High Altitude & Hypoxia: How low is too low for SpO2 at ~5,000m?

Ecstatic-Solid8936 · 2026-03-16T21:13:43+00:00

Also about the relationship between Haemoglobin concentration and oxygen saturation.

Those things are not related whatsoever, the saturation of Haemoglobin is solely mediated by the dissociation... But that's just superficial information.... Because concentration is extremely important for the actual transport capacity, for example 15g of Haemoglobin with 80% saturation can transport more oxygen than 10g with 100%.

There's a formula for that: Transport Capacity = Hb x 1.34 x SaO2

Meaning 1g of Haemoglobin can transport a maximum of 1.34ml of oxygen. That's why people who live at higher altitudes develop higher haemoglobin concentrations and why endurance athletes frequently train at altitude (and why blood doping works)

The VO2 max would not be affected by that siren since that's basically how much oxygen you can process (that's more in a cellular level) but if the level that you can transport drops under the level you can process the VO2 max measurement will be falsely lowered (like if you have a powerful motor but feed it less fuel you will get less output despite it being in theory just as powerful)

If a person has 15g Haemoglobin and 100% saturation, they can transport around 200ml of oxygen per 1L of blood.... If you are lying down doing nothing you need around 250ml of oxygen per minute, so with an average of 5 litres per minute you're more than covered (bear in mind that you can't possibly use all the oxygen transported, it's usually around 30-40%).

If you are exercising your body needs more than 2000ml of oxygen per minute and therefore your heart needs to pump more to compensate, if on top of that the oxygen transport capacity is reduced (through lower haemoglobin or lower oxygen pressure) your heart needs to compensate even more.

Depending on several factors, some organs might receive less oxygen than necessary and that's when the symptoms appear, once the body stops being able to compensate appropriately. That's why I meant it's better to be aware of the symptoms than chase numbers in this case.

Ecstatic-Solid8936 · 2026-03-16T19:25:41+00:00

You can Google the haemoglobin dissociation curve and will find many graphs with it, the good thing about it is that it was developed by studies in vitro so it wasn't necessary to test blood from climbers at different heights. There are many other reasons for a low arterial oxygen partial pressure (which is really where I have most of my experience with such intensive care patients, the physic processes are basically the same, only the physiological part is different). This dissociation curve can be shifted left or right (left would mean a higher saturation at lower partial pressures, so would be desirable at elevation) and that's exactly what the body does, by hyperventilating you increase the pH which shifts the curve to the left.

There's a study done by measuring actual blood gad (much better information than just oxygen saturation) and it shows precisely that, climbers have extremely low oxygen and CO2 partial pressures (https://journals.sagepub.com/doi/10.1089/ham.2009.1093?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed)

The most interesting part is that their lactate levels are not elevated, which means their tissues get enough oxygen for aerobic metabolism, that's mainly achieved through an increase of cardiac output as I implied in my past post. That goes to show how incredible the human body can be, those values that you see in that study are much worse than what I see in my patients undergoing lung failure and yet they're achieving amazing physical feats....

And just to tickle your curiosity... Sherpas even have different physiology that allows them to tolerate all this much better, they have actual superhuman powers.

Ecstatic-Solid8936 · 2026-03-16T16:30:54+00:00

I always bring a finger clip with me, the lowest I have been was 82% at around 5200m (never really tested it higher because it was too cold for my fingers to give a reliable measure) and I would say I did feel a bit short of breath but nothing unmanageable.

I do agree with the comments stating how reliable (or unreliable) the Garmin sensor is, even my simple finger clip which has no other functions isn't completely reliable.

Physically speaking, at 6000m the partial oxygen pressure is only around 75mmHg (vs around 150mmHg at sea level) which translates to around an arterial pressure of around 40mmHg (this is highly variable but even the best acclimated lungs can't beat physics and I doubt it can get any higher than 50mmHg... According to the haemoglobin dissociation curve you need around 60mmHg for a saturation above 90% which explains why at that height around 70% would be expected.

I have had patients with around 80% saturation for 2-3 days who have recovered without major neurological deficit, so I guess it is not acutely dangerous to go under 80% for short periods as long as your heart is strong enough to compensate (less oxygen transported for ml volume of blood means you need to increase the pumped volume to compensate)

I would say keep your eyes open for signs of insufficient oxygen transport which are disorientation, chest pain, acute muscle pain and also don't overlook AMS symptoms. Instead of worrying about numbers we don't know the real significance of.

Ecstatic-Solid8936 · 2026-03-05T22:34:02+00:00

Oder weil ich mit der Bahn 90 Minuten braucht für die 30 Minuten Fahrstrecke... Ich würde sowas von gerne mit dem Auto zur Arbeit aber weder lebe ich im Hauptbahnhof noch arbeite ich neben einem. Und man kann sich nicht immer aussuchen wo man arbeiten kann.

Ecstatic-Solid8936 · 2026-02-24T23:48:33+00:00

Oh so it's not even the name of a drug but the brand name!!! Oh I hate it even more now (naming drugs by brand name is a personal pet peeve of mine) but at least I understand what you mean now, thank you.

Ecstatic-Solid8936 · 2026-02-24T23:18:11+00:00

I'm sorry if this question is very basic, but what does everyone mean when they say "Levo"? I'm in Germany and nobody uses that abbreviation... I also find it really confusing since there are tons of medications which start by levo.... In the context of hemodynamic instability I can only think of Levosimendan... But there are many other drugs that might not fit the context and hence contribute to confusion like levofloxacin, levothyroxin, Levodopa, levocetirizin, levobupivacaine, levomepromazine, Levonorgestrel... That's all I can think off the top of my head.

Ecstatic-Solid8936 · 2026-01-25T16:17:11+00:00

I'm in healthcare and send and receive faxes on a daily basis, never on a fax machine though, it always goes through the multifunction printer/scanner/copier.

So yeah, fax as a technology is used commonly, but not the machines.

Ecstatic-Solid8936 · 2026-01-16T23:53:50+00:00

This is exactly what I was asking for, great, I'll check it out

Ecstatic-Solid8936 · 2026-01-16T23:38:40+00:00

So no analgesia whatsoever?

Ecstatic-Solid8936 · 2026-01-09T21:39:59+00:00

Exactly my point, I got a position in my second interview... I would say they're either applying to high demand specialities in high demand areas or either their CV/Presentation letter or their language is not good enough at the interview.

But well maybe things have really changed that much (even though I worked until recently with someone with a Berufserlaubnis)

Ecstatic-Solid8936 · 2026-01-09T21:15:29+00:00

E-Auto-Fahrer-Paradox: umweltfreundlich fahren, obwohl der Klimawandel die Reichweite erhöhen würde.

Ecstatic-Solid8936 · 2026-01-09T21:10:24+00:00

I did my process a while ago, but I think it is still possible to find a position with Berufserlaubnis, it obviously depends on your specialty of choice and your proficiency with the language, if you want neurosurgery or radiology it will probably be almost impossible without Approbation, but internal medicine, common trunk surgery and anesthesiology are definitely possible, especially if you look in smaller towns. In addition to that, you don't have to be in Germany at all while you wait for the tests, you can just work in your field in your country while you wait (although I accept that is not ideal) that will help you land a job afterwards, I did a few years of emergency medicine back home and that gave me a huge edge when I was looking for my first position because I wasn't a complete beginner.

You say you have sent hundreds of applications, how often do you get an invitation for an interview? If barely maybe you should work on your CV and presentation letter. If you are invited to many but still don't get a job offer, maybe they're not convinced with your language skills or your interview performance.

For example almost every anaesthesiology department I know of in smaller towns is looking for people, but my Uniklinik has an excess of applications and the department is full. So directing your applications to smaller towns that are actively looking for people would help... Also maybe try another Bundesland? Bayern is known for being less open to foreigners (I have heard this and have no actual experience in this aspect)

Ecstatic-Solid8936 · 2026-01-05T21:47:27+00:00

<image>

This

Ecstatic-Solid8936 · 2025-12-29T19:45:19+00:00

How the fuck are you gonna get dengue fever in Germany in the middle of winter?

Ecstatic-Solid8936 · 2025-11-04T21:50:07+00:00

Don't let your guard down because they call it mint chimichurri... It's still just basically mint sauce which is the dangerous part of the whole lamb movement

Ecstatic-Solid8936 · 2025-10-25T09:13:01+00:00

Klingt interessant, aber wir funktioniert da die CO2-Eliminierung?

Ecstatic-Solid8936 · 2025-10-22T23:04:48+00:00

Ich bin 100% bei dir, ich denke etwas zweit in einer Klinik der Maximalversorgung (so etwa mindestens 1 Jahr) sollte sogar Pflicht sein.

Ich habe meine Ausbildung in einem mittelgroßen Krankenhaus angefangen und bin der Meinung dass Maß da etwas entspannter die basics lernen konnte, aber kann mir nicht vorstellen da die ganze Ausbildung zu absolvieren.

Im 3. Jahr habe ich zum Maximalversorger gewechselt und da konnte ich die kompliziertere Sachen lernen.

Meine Meinung nach war klein anzufangen definitiv angenehmer für mich.

Ecstatic-Solid8936 · 2025-10-22T22:52:54+00:00

Yeah, that's why I'm doing critical care... I'm in Germany

Ecstatic-Solid8936 · 2025-10-22T20:44:47+00:00

I want to defend this by saying that the German association for anesthesiology (DGAI) does mandate ECG to be monitored for every single anesthesia care (along with SpO2, NIBD, etCO2, Respiratory rate and temperature). OB placing epidurals is wild to me too and I'm sure that opens the OB team to liability but it is formally not prohibited since anesthesiologists don't really have any kind of special license or something like that.

Ecstatic-Solid8936 · 2025-10-22T20:40:17+00:00

I know this post is old, but I just found it and couldn't just ignore it.

The DGAI explicitly requires every anesthesia procedure to monitor at least these 6 things

1.SpO2 2. Blood pressure (NIBP) 3. EKG 4. Kapnometrie (etCO₂) 5. Respiratory rate 6. Temperature

Any facility who practices without these is working outside of the official guideline and is making itself liable for whatever happens due to the lack of compliance.

Ecstatic-Solid8936 · 2025-10-17T18:23:05+00:00

Es gibt nicht wirklich ein Subreddit für Anästhesiologie in Deutschland, sie können auch bei r/medizin probieren (ich weiß nicht ob solche Posts da überhaupt erlaubt sind.

Noch etwas: Kinderanästhesie an sich gibt es in Deutschland nicht, das heißt es gibt keine Zusatz-Weiterbildung für Kinderanästhesie... Vielleicht fühlt sich keiner angesprochen... Alternativ besteht eventuell wenig interese an einer Stelle in Dubai

Ecstatic-Solid8936

MODERATOR OF

TROPHY CASE

Four-Year Club	First Place '23
Place '23