FiO2 and O2 Concentrators

[Rionoir, ADN, RN]

So we had a patient coming onto hospice the other day that was on 100% FiO2 on a BiPap (16/10, 20). Our inpatient unit uses oxygen concentrators and does not have wall oxygen. I had been told previously that we can't do super high O2 concentrations with oxygen concentrators, even linking multiple concentrators together. Using the estimating equation one would use in the hospital of 1L = 24% FiO2, and 4% for each additional L, theoretically two 10L concentrators hooked together would be 100% FiO2 but like I said I've also been told we can't do that high of a FiO2 with them.

So I called the RT at our equipment supplier who told me the max FiO2 possible with our equipment was 50-55%.

Some senior staff at the unit still insisted that the two 10L concentrators will give close to 100% FiO2.

Does anyone have any insight on this?

[chare]

1 hour ago, Rionoir said:

[...]

So I called the RT at our equipment supplier who told me the max FiO2 possible with our equipment was 50-55%.

Some senior staff at the unit still insisted that the two 10L concentrators will give close to 100% FiO2.

Does anyone have any insight on this?

Your RT is correct, combining the output of two concentrators is not going to double the delivered oxygen concentration.  When you blend two, or more, gas sources with an together you are not adding them together, rather you are blending them together. 

In your scenario, when you blend two gas sources, each containing 50% oxygen and 50% inert gas, this is going to result in a blended source of 50% oxygen and 50% inert gas.

Blending two gas source with different concentrations would result in a mix that was an average of  the two.  For example, blending one source with 50% oxygen and 50% inert gas with another source of 25% oxygen and 75% inert gas would result in concentration of 37.5% oxygen and 62.5% inert gas.

Best wishes.

 

[MunoRN, RN]

The concentrator removes the nitrogen in air leaving the air in the chamber about 95% oxygen, but room air is required to then flush that oxygen out of the chamber and produce flow, which dilutes it significantly.

The bigger question is why are you using such high oxygen concentrations in a hospice patient, considering hypoxia doesn't contribute to air hunger (there is a popular misconception that it does, but the fact that hypoxia isn't really noticeable is what makes it normally so dangerous).  In some cases the BiPAP may bring more comfort than discomfort, but adding oxygen only helps the patient to be more acutely aware of their air hunger, rather than alleviating it.

 

[Rionoir, ADN, RN]

1 hour ago, MunoRN said:

The concentrator removes the nitrogen in air leaving the air in the chamber about 95% oxygen, but room air is required to then flush that oxygen out of the chamber and produce flow, which dilutes it significantly.

The bigger question is why are you using such high oxygen concentrations in a hospice patient, considering hypoxia doesn't contribute to air hunger (there is a popular misconception that it does, but the fact that hypoxia isn't really noticeable is what makes it normally so dangerous).  In some cases the BiPAP may bring more comfort than discomfort, but adding oxygen only helps the patient to be more acutely aware of their air hunger, rather than alleviating it.

 

Thank you that makes total sense.

Trust me, if it were up to us we wouldn't be using vents and bipaps and airvos. The facility I work at is an inpatient unit for GIP LOC hospice patients. Patients and families are not always willing to discontinue all their hospital interventions when they come to us. We get full codes, tube feeds, fluids, pressers, you name it. Patients can be aspirating from tube feedings and families aren't always willing to stop them because they don't want to hear the explanations being given to them. Just like in the hospital, we can't force them to make the "right" decision.

Air hunger is rarely an issue for long though with the dose ranges of narcotics these patients are ordered, given that the family will let us give the proper doses, which is another issue. ?