Dual lumen cannulas

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Postby somnonaut » Wed Apr 18, 2012 7:59 am

The dial is a stupid dial on the top of the cylinder with precast liter flow markings. You dial in 1 LPM. No feedback mechanism. It is regulated flow of 1 LPM. Always struck me as odd that there is no feedback mechanism.
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Postby bduce » Wed Apr 18, 2012 8:02 am

Yeah had a look, it is similar to our resus trolley cylinder. Probably not appropriate for study titrations.
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Postby Rick » Thu Apr 19, 2012 8:15 pm

When using an oxygen source whose flowmeter is attached to a 50 psi supply, what the indicator show is what flows.
HOWEVER,that flow is what is coming out of the orifice of the flowmeter, if you connect a smaller bore tube, the flow will be more in that tubing, same amount of oxygen but the flow increases to get the volume through the smaller orifice available. If you increase flow to the point that the tubing cannot accept it, the flowmeter will not show an increase, stated differently, if you are at 10 lpm and the tubing cannot support more flow and you turn the flow up, the indicator will not move, most likely the tubing will pop off the flowmeter at that point.
I have tested small cannulas, with both prongs working and felt that a flow of four to five liters was literally painful, it was a pressure cannula, not an oxygen cannula.
Hope this made some sense, pain meds are kicking in, thankfully.
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Postby somnonaut » Thu Apr 19, 2012 10:12 pm

The flow ends up being venturi'd to the force of a sandblaster I figure. Right Rick?
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Postby munkyBeatz » Tue Apr 24, 2012 1:47 am

I agree with Rick on this one. I worked in home DME for a little before sleep, and nearly all O2 conservers use a dual lumen cannula to detect inspiration/expiration to allow for longer use of an M-tank or E-Tank. The Rx setting's do not change with those items, however I do remember when patients would use these same cannulas on continuous flow settings they would complain of irritation in one nostril. You can also physically feel the difference if you have a two running side-by-side [one dual cannula, and dual-lumen pushing from one]. You can feel the difference on your hand, even more so if your hand is wet.

I was looking for "actual" evidence, not just subjective and really couldn't find any online. However, I did come across this article that does help substantiate that the Rx is still the same from dual lumen cannulas. This artical talks about hooking up two different O2 sources to a single cannula, to double the intake of hypoxemic patients.

http://meeting.chestpubs.org/cgi/conten ... 0/4/245S-a

It's not really the 'smoking cannula' you were looking for, but it provides some evidence outside of the subjective realm.
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Postby munkyBeatz » Tue Apr 24, 2012 1:52 am

I forgot to get more to the point in my post.

In short, yes I believe that although O2 output is reduced to a single nostril/cannula that it still produces the same LPM value as when using two nostrils/cannulas. The difference is, the PSI rating that is elevated from using a single cannula to deliver the same LPM value. As Rick stated, the concentrators will compensate for tubing/resistance.
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Postby nowhere » Tue Apr 24, 2012 3:24 am

Ok this kinda gets "off-subject" but you're talking about those like, Salter cannulas that serve as a O2/ETcO2 monitor/delivery device?

And...... off topic, we have ResMed CPAP machines which, give you the precise amount of pressure that's going to the patient on the little screen techs have on the desktop while doing titrations; by the way, I was told to ignore any of those "extra" settings; it's not my business, they say(supervisors). But I'd sure like to know what you find out.
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Postby Rick » Tue Apr 24, 2012 7:59 pm

Original post:
When using the dual lumen cannulas to administer O2 WHILE recording ETCO2, do you take into account the lower flow out of the cannula (only one nostril) for the "prescribed" O2 flow level. Meaning, do you crank up the oxygen to a higher level to deliver the same end stream O2 concentration being that it is only coming out of one tube of the cannula?

ANSWERED!
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