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Monday, June 16, 2008

The basics of oxygen therapy: Part 1

To view rest of series, click here.

As I've written before, I think I've spent more time debunking oxygen myths and educating about oxygen than anything else I have to teach regarding respiratory therapy stuff. And I'm not talking patients.

Don't get me wrong, I don't have a problem with this, nor am I implying that nurses are stupid. I think one of the big differences in RN school and RT school is that RN school covers a little about a lot, and RT school teaches a lot about a little.

Sure, oxygen therapy is covered in RN school, but only briefly. Which explains why we RTs have to explain the basics from time to time.

Respiratory Therapy Driven has good post today about some RT basics. A non-rebreather, for instance, is ideally supposed to deliver 100% FiO2, but because of the slim chance the oxygen gets shut off, the masks come with one one-way valve instead of two. Thus, the FiO2 obtained is only 75%. But try explaining that 100 times.

"Yep, chart 100% if you want," is what I usually tell them now. This gets to be a tricky thing to explain at three o-clock in the morning.

We have one old school doctor who orders a bubbler with every nasal cannula order, but our protocol states that one is not needed unless the flow is 4LPM or greater.

And like Djanvk wrote, all our post op patients are ordered up on 2-3LPM times 24 hours. What's the deal with that?

We estimate adult nasal cannula FiO2s based on the following formula:
  1. 2LPM = 28%

  2. 3LPM = 32%

  3. 4LPM = 36%

  4. 5LPM = 40%

  5. 6LPM = 44%

However, don't dare put a nasal cannula on a three week old baby at 6LPM. That would be the equivalent of an adult sticking his head out the window while traveling 60MPH down the highway

We have a special flowmeter now that maxes out at 3LPM to prevent someone from accidentally (or purposefully) turning up the flow too high. Then we start at low as 1/4 LPM. Obviously, increasing to maintain a specified SpO2 (in my opinion 92%, but most of your docs like 94%.)

The reason I bring this up, and actually the reason for this blog post, is I'm curious to know what the estimated FiO2s would be for neonates and smaller children. It can't possibly be the same as for adults.

I have never found the answer on the Internet nor in any RT literature. I asked the question on once, and no one there knew the answer either.

Maybe nobody cares but me

My guess is it would be something like this:
  • 0.5LPM = 28%

  • 1 LPM = 32%

  • 1.5LPM = 36%

  • 2 LPM = 40%

  • 2.5LPM = 44%

Of course I'm just making these neo numbers up. Technically speaking it really doesn't matter what the FiO2 is, so long as you're maintaining a sat, but I'm still curious.


KokomoCRT said...

I love it when the RN charts a venti mask or aerosol in liter flow- now whats that gonna tell us?

Wendy said...

Very interesting post. I haven't been around for a while - and look what I've missed!
Being a nurse myself, you make an excellent point - we learn a little about a lot. So, I did not know about the humidifier (bubbler) at less than 4LMP. Nor about the 75% 02 and the one-way-valve mask. I used to chart 100% too!
And, I've seen my co-workers adjust somebody's 02 rate without checking with respiratory therapy. In the hospital where I used to work, you always had to check with the Dr. or the Resp tech. Simply because they knew their stuff.
There was a time when nurses did not draw blood. We had lab techs. for that. We could only monitor oxygen therapy - never give treatments. Now we are expected to do almost everything. I certainly don't mind learning new skills, but I must say that the techs are better at it than we are.
Thanks for this post. I will stay tuned.....

Intubate Em!!! said...

Calculating a baby's fio2 is much more complicated.

This what we use at my hospital.

Mind Body Shop said...

My ideal relaxation is working on breathing exercise. I spend hours in junk shops buying furniture. I do all the upholstery work myself, and it's like therapy.

Amy said...

Here's what I'm curious about---and it's not about pets and asthma this time!---what's the average RT's take on fun oxygen "masks" for kids? I ask b/c in a hospital stay when my kid was younger, the ped. staff used a blow-by nose and mouth cartoon mask, as they figured the cannula might freak her out too much.

Which was a nice thought, only she didn't get enough oxygen out of the thing and it set her recovery back a couple of days---and ended up on the cannula, anyway. (Which yes, totally freaked her out, as I'm sure you know.)

I don't believe it was an RT who put the mask on her, although I wasn't there during her admission. Just wondering about your take b/c it seemed completely counter-productive to me!

Freadom said...

Intubate em: Thanks for the formula.

Amy: I've rarely had a problem putting a nc on a kid. And I think they'd tolerate a nc far more than a mask - in most cases. However, with kids you kind of go with the flow.

Sometimes we do use blowby oxygen if they absolutely can't tolerate the nc. Does this answer your question?