Nick Mark MD Profile picture
Nov 11 5 tweets 2 min read
Nomenclature question: what do you call it if someone has an elevated PaCO2?

1/
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.

2/
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 👎

🤷
3/ Image
So saying hypercarbia is a linguist faux pas the likes of using the wrong salad fork. Who cares?

Well … it might be better to say hypercapnia just to avoid someone tendentiously correcting you - or writing a letter to the editor.

H/t @doc_BLocke for the example!

4/
Ugh typo. Second one should say hypercarbia.

(FYI When I post this 🧵on #medmastodon there’s an edit button!)

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More from @nickmmark

Nov 11
Ok so #TwitterChaos is hilarious & as a bonus we’ll never need to see adds from these companies on Twitter again.

1/
Continued…
Nintendo
Read 4 tweets
Nov 9
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 🧵
1/
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…
2/
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-…
3/
Read 8 tweets
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🧵.
2/ ImageImageImage
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?
3/ Image
Read 20 tweets
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?

1/
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!
2/ Image
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…
3/ Image
Read 15 tweets
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

1/
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
2/
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.
3/
Read 12 tweets
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
Read 5 tweets

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