Link To YouTube Video From PulmCrit-“10 minute talk on hypoxemia physiology”

In this post, I link to and embed Dr. Josh FarkasPulmCrit YouTube video, 10 minute talk on hypoxemia physiology, Sept. 8, 2021.

I recommend that you watch Dr. Farkas lecture on YouTube [link is to the YouTube video] because, on the YouTube video, you can follow along with the excellent autogenerated transcript.

All that follows is from the above resource.

Here is a 10-minute video I [Dr. Josh Farkas] made for the Cooper Critical Care Conference.  It explores some basic & useful concepts about hypoxemia physiology, including how to apply this at the bedside.  The algorithms in the video aren’t intended to be strictly followed, but rather merely as general conceptual schemas.

related

  • For more information about the disutility of ABGs in evaluating the cause of respiratory failure, see this prior blog.
  • A more detailed discussion about hypoxemia physiology in the context of shunting may be found here.

What follows are some screenshots from Dr. Farkas’ YouTube video with accompanying  text from the autogenerated YouTube transcript.

00:22-00:28
There are only really three mechanisms
of hypoxemia that you need to worry
about: hypoventilation, vq mismatch, and
shunting.
00:28-02:38
Shunting in hypoventilation the alveoli
and the bronchi are working perfectly
and the problem is simply there’s not
enough ventilation getting to the lung
so the alveoli are burning through
oxygen faster than they’re getting
oxygen probably the most commonly
encountered cause of hypoventilation is
a central brain drive problem where the
brain is simply not stimulating the body
00:48
to breathe and we’re most familiar with
00:50
this probably in the context of opioid
00:52
intoxication so folks come in their
00:53
respiratory rate is low they’re
00:55
substantially altered they’re not
00:56
breathing this is relatively easy to
00:58
diagnose other causes of central
01:00
hypoventilation are folks with brain
01:02
stem strokes or substantial brain
01:04
pathology and once again relatively
01:05
straightforward to diagnose on the basis
01:07
of substantially altered mental status
01:09
so the second type of hypoventilation is
01:11
a respiratory mechanical problem where
01:13
the brain is stimulating the body to
01:15
breathe but the body is unable to
01:16
breathe either due to a tracheal
01:18
obstruction or upper airway obstruction
01:20
or neuromuscular problem involving the
01:22
diaphragm in the chest ball for patients
01:24
with acute respiratory mechanical
01:25
problem they will compensate for this
01:27
with tachypnea and they will only
01:29
develop hypercapnia and hypoxemia when
01:32
they’re really on the brink of death so
01:34
most of these patients will present with
01:35
tachypnea and they’ll be struggling to
01:37
breathe but they won’t necessarily be
01:39
substantially hypercapnic nor hypoxemic
01:41
and things of this nature would include
01:42
epiglottitis acute transverse myelitis
01:45
gumbray syndrome neuromuscular problems
01:47
things like periodic hypokalemic
01:49
paralysis so some sort of acute
01:50
neuromuscular or airway catastrophe and
01:53
once again these patients are not really
01:55
going to present with hypoxemia usually
01:57
they will present with almost like an
01:59
exfixial problem so the last cause of
01:59
exfixial problem so the last cause of
02:01
hypoventilation is a chronic respiratory
02:03
mechanical problem and this can be very
02:04
difficult to diagnose so these are folks
02:06
with for example chronic muscular
02:08
dystrophy or chronic obesity
02:10
hypoventilation syndrome and what
02:11
happens here is that the brain adapts to
02:14
a higher level of paco2 so the brain is
02:16
kind of okay with this and it doesn’t
02:18
really stimulate the patient to drive
02:20
their respiratory rate too too high so
02:22
patients may show up on a couple liters
02:24
of oxygen and they’re not an extremist
02:26
they don’t look too bad most of these
02:27
patients can be diagnosed because they
02:29
may be carrying some sort of chronic or
02:31
obvious diagnosis of a neuromuscular
02:34
problem but occasionally very rarely you
02:36
might encounter this for the first time
it can be a little tricky to find this.

 

 

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