(The real reason) Why COPD patients get low-flow O2

nasalcannula_dummyWith brand-new EMT students riding with me, I like to take a moment to explain why many of our “shortness of breath” patients are likely to receive a nasal canula instead of a NRB cranked to 15lpm. We talk about baroreceptors and chemoreceptors and the hypoxic drive and how they’re likely to see a question about COPD patients and oxygen administration somewhere along the line.

Turns out that’s all wrong.

LifeInTheFastLane sent an email with their most-viewed articles of 2015, and this one, Oxygen and CO2 Retention in COPD, was right at the top. And for a good reason.

The gist of it: increased O2 administration causes vasodilation of normally constricted vessels leading to poorly ventilated alveoli. This causes a V/Q mismatch. Also, the Haldane Effect.

The next time you have a student or are oxygenating a COPD patient, consider why, and get that hypoxic drive stuff out of your head.


Pulmonary Embolism. Do we care?


First of all, free up two hours of your time and listen to this: Smart EM Undoes PE.  Now head over to EM Lyceum to read their evidence-based blog post about diagnosing and treating PE in the ED setting.

(Ok, I don’t really expect everyone to be able to do that, but they’re great sites and will help in understanding pulmonary embolism much better.  Even if you don’t check those out, keep following along and check out how the mortality associated with PE may be greatly overstated and know that there is only one not-very-good study to support anticoagulants for treating PE).

Now that you’re extremely well informed on the problems associated with PE diagnosis and treatment, we can have a conversation about what that means for the prehospital provider.  In their podcast, Dr. Newman and Dr. Shreves discuss how they as physicians can have very little wiggle-room to change their practice in the emergency department (due to our medical-legal culture).  So what can we do?

Interestingly, it seems as though we can only improve our practice when faced with PE.  If you consider that the role of EMS in many instances of acute injury and illness is recognition and activation of the system needed for definitive treatment (I’m thinking code stroke, code STEMI protocols), perhaps prehospital providers can play a similar role in identifying PEs.

For example, look at the Wells’ Criteria, one of the go-to diagnostic tools used to identify PE in the emergency department.  EMS providers are certainly knowledgeable and skillful enough to go through each of those scoring criteria, even if we don’t have the ability to do d-dimer testing in the field (a blood test that, when combined with a rule out criteria like the Wells’ Score, eliminates the need for further testing).

Or maybe that isn’t so crazy.  There’s an interesting study that was done in Slovenia where researchers used the Wells’ Criteria, End-Tidal CO2, and a field D-Dimer to diagnose (or at least effectively rule-out) PE prehospitally.  Basically, if a patient has a low clinical probability of having a PE (low Wells’ score) and has a PetCO2 > 28mmHg, they can be safely ruled out of having a PE even if their D-Dimer was positive.  And if they were clinically suspected to have PE and had a PetCO2 < 28mmHg, those patients were pretty likely to have a PE (93% specific for positive PE).

The question is, at the end of the day, what does it matter?  If Smart EM came to the conclusion that they, as physicians, have little ability to change their practice, AND, if they did, they would be doing even less testing/treating for PE than they do now, why should a paramedic carry around a card with the Wells’ Criteria on it?

It might not change our treatment today or tomorrow, but having a better understanding of this disease process may just help better diagnose patients before they get to the ER.  Or it might help to move the train of thought from PE to some other respiratory disease that we can treat.

I think this is certainly a point for conversation, and I’d love to know what you think.  Especially considering the limited resources available for training prehospital providers AND operating under the presumption that paramedics would like to move into a more professional realm, what is our responsibility for recognizing/interacting with diseases such as pulmonary embolism that are beyond our treatment capacity?

PE Reference Bits