Today on the podcast, I interview Martin Tobin on 3 papers he has recently written on COVID pulmonary physiology.
Martin Tobin
Caution about Early Intubation in COVID-19
p-SILI
From 2 studies, 1 on sheep breathing with a human-equivalent Vt of 502 ml
2nd study was observational with a questionable connection to Vt–it was confounded by a number of other factors
Absence of Obtundation
L vs. H Subtypes
Physio Diversion – Looking for the Patient that needs more Inspiratory Flow
Basing Respiratory Management of COVID-19 on Physiological Principles
Tachypnea in Isolation is Not an Indication for Intubation
Not indicative of increased WOB
Avoiding Intubation with NIPPV
Correlation of saturation with a host of other evils, but it is possible that the saturation is merely a marker–similar to pH. Vicious cycle of shunt, low SvO2, encephalopathy, decreased resp. drive. COVID has been different, with decreased saturation without the horrible lung injury that normally accompanies it. We are also used to patient discomfort from the disease causing the hypoxemia. Retained good compliance. We have not seen the isolated hypoxemia of COVID in many situations before.
The Baffling Case of Silent Hypoxemia
Happy Hypoxemia vs. Silent Hypoxemia
Dr. Tobin defines silent hypoxemia as PaO2 < 60 mmHg with a PaCO2 >39 mmHg (as a PaCO2 < =39) blunts the dyspneic response to hypoxemia
Why don't they have dyspnea vs. why do they have such severe hypoxemia unaccompanied by the degree of standard badness that normally accompanies it
They do not crump
They don't develop multi-organ
Dyspnea
Purely subjective
Advanced age and diabetes may blunt dypsnea
Increase in 10 of PaCO2 causes extreme air hunger
Increase Ve when PaO2 <60, but severe hypoxemia elicits increase in ventilation only when PaCO2 > 39 mmHg [32539537]
Definition of Hypoxemia
Do we need to factor in FiO2? Dr. Tobin and I say no!
I define by pulse ox or (PaO2), doesn't matter how much O2. e.g. “He is still hypoxemic despite being placed on NRB.”
When does Hypoxemia Become Dangerous?
Pulse Ox Inaccuracy
OxyHemoglobin Dissociation Curve Shifts
Fever shifts to the right, Decreased CO2 shifts left
Mechanism of Silent Hypoxemia
ACE2 is expressed in the carotid body and may be partially to blame
COVID breaks our Heuristics
Heuristic representation of how bad their lung disease actually is. Projecting expected course…
COVID first disease that unlinks it
Additional New Information
- HOT-COVID shows targeting Pao2 of 60 vs. 90 had days alive without life support benefit []
More on EMCrit
- PulmCrit – Understanding happy hypoxemia physiology: how COVID taught me to treat pneumococcus(Opens in a new browser tab)
- Pulse Oximetry Questions!(Opens in a new browser tab)
Additional Resources
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Professor
Nassau University Medical Center
No conflicts of interest (coi).
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Very insightful. Changes some of what I thought I learned in fellowship regarding hypoxemia and lung physiology
Great podcast. Do you have links to the evidence regarding safety of non-invasive PPV in COVID?
Great podcast/article. Could you please post citations for the evidence regarding safety of non-invasive PPV in COVID?
Sorry, didn’t realize the first one posted!
Fantastic discussion. Tobin is a giant in pulm/cc medicine. His pearls of wisdom were simple yet powerful clinical tools/reminders. Strong work Scott.
is it possible to have the audio information in a text
Superb!!
The knowledge of Martin is fantastic, always bringing deep theory with practical medicine. A pleasure and a honor listen to him.
Thanks Scott for the opportunity.
Thank You Dr. Martin Tobin,
I could hear your passion and concern about Teaching the public medical information regarding George Floyd’s death. Your Truthfulness and Educational spirit spoke Loud. The Black Community needed Medical Truth, GOD Used your VOICE…
& The World LISTENED. May this be a new beginning for BLACK JUSTICE. Our Ancestors such as we Thank You. Volunteering Love doesn’t go unnoticed.
amazing discussion and understanding. Thank you for the post