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Sunday, June 15, 2008

The hypoxic drive theory: Should be still taught

(This is part six of a six post series. To view entire series click here. )

I'm enthralled with this hypoxic drive theory, so I have to make one more post about it, and then I will probably never mention it again. But I can't help but to delve into this topic, to smell it, to read Jeff Whitnack's rantings with awe.

After all, I have been on a rampage myself on my own RT Cave blog about bronchodilator reform. I think doctor's and nurses have been inculcated with the idea that bronchodilators are indicated for everything pulmonary, when they are really only indicated for COPD and asthma.

So, I can hear Whitnack's frustration.

He writes, "When I bring up my arguments against the hypoxic drive, often I feel as if I am arguing religion and not science."

I feel the same way when I argue for bronchodilator reform. I often feel as though I'm blowing into the wind, and will never win. However, I cannot stop trying.

There is a reason I wanted to make this one last post about the hypoxic drive, and it has to do with this quote from Whitnack's RRT Page: "I have asked local RT instructors their opinion. One said, 'I don't believe in it (CO2 retainer/hypoxic drive theory), but I've got to teach it.'"

I discussed my opinion about the hypoxic drive theory being a fallacy with one of my RT students a few weeks ago. After I brought it up with her I wished I had not, because I decided I shouldn't confuse her, considering she would be taught the hypoxic drive theory in school, as I was by her same teachers.

However, she came back the next week, and she reported that she told her teachers about what I said.

She told me her teacher said this: "There is a lot of evidence against the hypoxic drive theory, and we are actually thinking about not teaching it anymore."

That is definite progress.

However, I would have one thing to say to this teacher, which may surprise you guys:

I would not stop teaching the hypoxic drive theory.

Are you shocked that I'm saying that?

Well, actually, you wouldn't be if you read my other blog. Because I believe that all theories should be taught in school, and that the students should be allowed to decide for themselves which is real and which is fallacy.

Because, after all, these are just theories. And, either way, there will still be doctors for years to come who are "brainwashed" into the idea that the CO2 retainer/ hypoxic drive theory is as real as the screen you are reading this on.

For no other reason, the hypoxic drive theory must be taught so new RTs aren't befuddled by a doctor's insistence that low oxygen levels are okay.

Overall, as per this slide show: (source unknown) "Health care providers need a clear understanding of the risk factors associated with oxygen induced hypercapnia... This knowledge needs to be applied in clinical practice to select patients to be identified at risk for oxygen induced hypercapnia instead of withholding treatment to all patients with the diagnosis of COPD"

Anyway, I hope my posts, coupled with Whitnacks, and other sources floating around or available for free on the Internet, will help make other RTs, RNs and doctors, and -- probably more important -- teachers aware that the hypoxic drive theory has been "debunked," and replaced with a greater concern, which is oxygen induced hypercapnia.

Wait!! There is one more thing that is more important than what we RT thinkers think: the patients. If we can show that it is okay to have a COPD patient on more than 2 LPM, then the person who benefits is the COPD patient.

I lied about one thing. I WILL definitely bring up this hypoxic drive theory again, as I have just recently been contacted by a COPD patient who personally does not believe in the theory. As soon as she gives me permission, I will write more. Her story is very inspirational.

Thus, more coming... (to view all articles on hypoxic drive, click here)

Further reading:  The Hypoxic Drive Theory:  A Hystory of the Myth


gutterpup said...

Put a retainer on a nonrebreather, watch him stop breathing and then see how much you care WHAT they call it.

Anonymous said...

The examples you have given were clearly not good examples nor representations of the general COPD population. Of course, in medicine and biology almost anything can happen, if you have seen anything other than respiratory cases. That's why it becomes important to conduct studies instead of giving anecdotal evidence such as yours. In fact, while COPD patients are classically taught to be retainers, only a minority are. You have merely quoted a single non-retainer for this article. Reason 1: V/Q mismatching -> Let's see now. If we increase surface area by which to eliminate CO2 how does that cause a rise in PaCO2? Traditionally it's been taught that a high V/Q ratio gives a lower CO2. I believe this reason is not a good one. Also you said patients die on hypoxia rather than hypercarbia, which is fair enough. But, you quoted a patient who survived 4 days on high flow O2. Now, did you quote the patient if he survived on low flow O2? Maybe he would have survived just as long. You don't have a valid comparison for that statement. Furthermore, a good outcome is also dependent on morbidity not just mortality. Did the patient get more acidotic and drowsy on high flow O2? You don't know that. So please next time back up any examples with a good control if you want to use them as evidence. Personally I have no objection with high flow O2 on COPD patients, but if they deteriorate it may be better to keep a low flow. I do believe that the hypoxic drive theory exists but not to the extent most doctors believe it does. Also, correct me if I'm wrong, but it also seems you are merely trying to sound controversial in this article.