What's up everyone, it's Jessica, and welcome to CritIC: the acid-base series.
In this video you'll learn an easy approach to respiratory acidosis.
Let's get into it.
When there is an increase in carbon dioxide, the Henderson Hasselbalch equation teaches
us that the equation shifts to the right, increasing hydrogen ions in our body and thus
becoming more acidic.
This is respiratory acidosis.
In normal physiology, when our CO2 levels rise, our respiratory center triggers us to
start breathing!
So an elevated pCO2 is an indication that that's not possible.
Either because our respiratory center can't be triggered (in central nervous system depression),
or because we can't physically breathe.
Let's break these down.
Our respiratory center is located in the medulla oblongata and the pons of our brain stem.
Chemoreceptors detect high CO2 and will trigger the body to increase respiratory rate.
When the respiratory center is depressed, it won't function properly, and CO2 levels
will rise, resulting in respiratory acidosis.
Common causes for CNS depression are drugs like opioids and benzodiazepines, as well
as brain damage caused by trauma, tumors or ischemia.
In order to physically breathe we need to have functioning respiratory muscles and an
open airway.
It then follows that neuromuscular causes and airway obstruction can cause respiratory
acidosis.
Examples of neuromuscular disorders that prevent adequate ventilation are critical illness
polyneuropathy, ALS, Guillain-Barre, etc.
However, a common neuromuscular cause you may never forget is exhaustion, after a patient
has been breathing heavily for a while.
Examples of upper airway obstruction are blockage by the tongue (in sedated patients, so they
have 2 reasons to have a respiratory acidosis!), tracheal stenosis or obstruction by a foreign
object.
Examples of lower airway obstruction are positional asphyxia, when people are restrained, but
more commonly in asthma or COPD.
The asthma but especially the COPD patient always has some form of lower airway obstruction.
Therefore, they're used to higher CO2 levels than those without.
This has 2 consequences: First, they always have a slight respiratory acidosis, which
they compensate metabolically (high bicarbonate).
Secondly, they don't use carbon dioxide as their primary trigger to breathe, but oxygen.
So whenever you apply oxygen to a COPD patient, please remember you're removing their trigger
to breathe.
So be careful.
So why is this important?
Respiratory acidosis is a sign of inadequate breathing.
And as you well know, inadequate breathing can lead to an early grave.
Also, high CO2 levels causes CNS depression itself, so you're in a vicious cycle!
Use the ABCDE approach for the primary assessment.
Two rules: if they're awake, make them breathe.
If they're sleep or if they can't, intubate!
If you suspect a drug overdose, consider antagonizing it.
Naloxone for opioids, flumazenil for benzodiazepines.
If it's caused by brain trauma, secure the cervical spine, get an anesthesiologist to
intubate and get a CT scan asap.
If it's caused by airway obstruction, try to figure out if it's upper or lower, and
consider nebulizing for the latter.
Neuromuscular causes may require intubation as well.
That's it on respiratory acidosis.
Drop me a line in the comments below with your feedback!
Thank you!