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Nick Mark MD

@nickmmark

Nov 11

Nomenclature question: what do you call it if someone has an elevated PaCO2?

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Medically they are synonyms. Both terms - hyperCAPNia & hyperCARBia - *mean* the same thing: having an increased PaCO2.

But the difference is a really big deal if you are a linguist.

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Etymologically, there is a (silly) difference:

Hypercapnia comes from the Greek word hyper (high) + the Greek word kapnos (smoke); both Greek roots 👍

Hypercapnia comes from the word Greek hyper + the *Latin* word Carbos (meaning charcoal); 1 Greek + 1 Latin root 👎

🤷
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Nick Mark MD

@nickmmark

Nov 9

https://twitter.com/nythealth/status/1590375916076560384

I’m all about using comparative physiology to understand critical illness but I gotta call BS on this.

The “mysterious EEG pattern” they described is burst suppression & the most likely explanation for it (and the mysterious prolonged unconsciousness) is OVERSEDATION.

A 🧵
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https://twitter.com/nythealth/status/1590375916076560384

They claim that deep sedation is neuroprotective based on a *theoretical* model of burst suppression.

We know for *actual studies* done in the ICU that the opposite is true: burst suppression in critical illness is associated with increased mortality.
ncbi.nlm.nih.gov/pmc/articles/P…
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https://twitter.com/nickmmark/status/1346608067325005824

I’m all about the Painted Turtle & what we can learn from it - I’ve even written & given Grand Rounds on this subject! (See this🧵 & link below for example)

But the analogy of C Picta belli to critically ill humans is deeply flawed.

GR lecture: onepagericu.com/blog/from-zoo-…
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https://twitter.com/nickmmark/status/1346608067325005824

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Nick Mark MD

@nickmmark

Nov 2

More fun pulmonary physiology:

🤿A person takes a deep breath of ambient air & free dives (e.g. holds her breath without a SCUBA tank) in the ocean. At a depth of 40m an arterial blood gas is drawn.

Compared to an ABG drawn at the surface, the divers PaO2 at 40m is:

The answer is INCREASED.

We know because people have free-dived with an arterial line: mean PaO2 at 40m was 197 mmHg (after 45s of breath holding!)

ncbi.nlm.nih.gov/pmc/articles/P…

But why? Understanding requires a deep dive into the alveolar gas equation. A 🫁 pulm #physiology🧵.
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Before getting to the fun stuff, we should acknowledge that it’s *weird* for your PaO2 to increase while breath holding.

For comparison look how PaO2 DECREASES if you hold your breath on land: it plummets from 110 to 60 mmHg in just 35 seconds!

What makes diving different?
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Nick Mark MD

@nickmmark

Nov 1

Here’s another pulmonary physiology question that *everyone* who gives O2 to patients ought to know:

What is the primary mechanism by which supplemental oxygen can increase PaCO2 in someone with severe COPD?

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This is a hard question! You probably learned that "its bad to give someone with COPD ‘too much’ O2 because they might stop breathing”

Turns out hypoxic respiratory drive causing apnea is a MYTH..but there is an important truth here:

A🧵on Oxygen induced hypercapnia!
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Every myth has a little kernel of truth:

In the 80s it was shown that giving people with severe COPD (GOLD stage IV) high flow oxygen (15 lpm) made their minute ventilation (VE) drop then return (almost) to normal, but PaCO2 rose significantly.

Why?

ncbi.nlm.nih.gov/pmc/articles/P…
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Nick Mark MD

@nickmmark

Nov 1

What is #MedMastodon & why might we need it?

A short thread explaining what it is & why I think it’s time to consider moving to a free, self-moderated medical community as a #MedTwitter alternative.

med-mastodon.com/web/home

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Despite its flaws I think Twitter is a great platform for medicine/science.

It’s a fantastic way to follow breaking news & scientific pubs. It’s a great way to hear what brilliant people think. It can be an OK way to engage in debate.

I’m a better doc because of #MedTwitter
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Where else can you see the moment impactful research is published? Or hear the authors explain it & discuss with them?

Where else can you hear about the experience of colleagues around the world?

I’ve learned a lot and made some great friends IRL on here.
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Nick Mark MD

@nickmmark

Oct 31

Hi #MedTwitter friends -

Hoped it wouldn’t come to this but I just setup med-mastodon.com as a #MedTwitter alternative.

Trying to create a free, open community for sharing & discussing medical topics. Join & create your own free verified account.

Some advantages of mastodon:
- open source, decentralized platform
- a small community that can moderate itself (that means no hate speech, no misinformation)
- 500 characters per "toot"
- built in content warnings & enhanced privacy settings
- cross platform compatible
- free

Working URL

med-mastodon.com/about

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