So we used a mean guy on twitter to spur a discussion on Oxygenation Physiology and talk about when PaO2s are necessary and you can't use the pulse ox (hint: not often). My discussant is Alex Yartsev.
Alex Yartsev (BappSci(MRS), MClinED, MB.BS, FCICM) is an Intensivist from Westmead ICU in Sydney, where he leads the ICU education program. He also coordinates the Mechanical Ventilation unit of study at Sydney University and acts as a Second Part examiner for the College of Intensive Care Medicine.
He is also the creator of Deranged Physiology, a beautiful free resource on clinical physio.
The Oxygen Cascade from Lung to Mitochondria
PaO2 Builds the Sat and the Sat Oxygenates the Tissue
— Landsberg Manual (@LandsbergManual) April 20, 2023
Do We Need an ABG to assess the cause or severity of lung disorders
Does an ABG help assess tissue oxygenation when compared to pulse ox? What is the Best Representation of Tissue Oxygenation
-PaO2 of 90 mm Hg, but Hb of 4 g/dL
Do ABG Machines Measure Saturation or Calculate It?
The First Tweet
Hb sat is a by product, no cell in the body senses hb sat… pao2 is sensed, pco2 is sensed, pH is sensed. Those who target a Hb sat..plz explain?!#Anesthesiology #EmergencyMedicine #meded #MedTwitter #CriticalCare#pulmonary #Anesthesiology #cardiotwitter #EmergencyMedicine pic.twitter.com/RjUml9BZgW
— Landsberg Manual (@LandsbergManual) April 13, 2023
CO2 is just a representation of Alveolar Ventilation in the Alveolar Gas Equation from David Story, MD
Fails, b/c PaO2 doesn't save you if the PaO2 was a little higher, same horrible physiology which would go unnoticed, you need to understand severe alkalosis, not look at a PaO2
3 reasons it's RIDICULOUS to say spo2 beats ABG
1) SpO2 estimates SaO2, often poorly
2) SaO2 is a product of PaO2 & pH, yet pH is tightly regulated NOT in relation to O2, so it can't be the true goal of O2 Rx
3) The brain senses and protects a pao2 of 60@emcrit @meded @crickets pic.twitter.com/cZH4mVmfhH
— Landsberg Manual (@LandsbergManual) April 27, 2023
Tweet 4 – These Tweets Speak for Themselves
Pulse Ox Fails
See the IBCC Chapter on Pulse Ox/ABGs
Hypotension and Pulse Ox
Additional New Information
More on EMCrit
Now on to the Podcast
- EMCrit 358 – Dizziness Makes Me Dizzy Still! – GRACE-3 and more with Peter Johns - September 24, 2023
- EMCrit RACC Lit Review – September 2023 - September 17, 2023
- EMCrit – Lessons from a Master Trainer – Cliff Reid on Training Team Performance - September 11, 2023