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CPAP with PS versus NIPPV

Discussion in 'Clinicians [ RN / NP / PA ]' started by Paseo Del Norte, Jun 4, 2011.

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  1. Paseo Del Norte

    Paseo Del Norte

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    Hello everybody, I have a question for you respiratory gurus.

    Where I work we have a new ventilator that can provide both CPAP and NIPPV (AKA BiPAP). Both modes can provide non-invasive therapy to spontaneously breathing patients. My question comes down to the following; is there any significant physiological difference between CPAP + PS and NIPPV?

    With CPAP + PS I have a pressure low, the underlying CPAP and a pressure high, the PS which is above the CPAP.

    With NIPPV I have a pressure low, the EPAP and a pressure high, the IPAP.

    As far as I can tell, these methods provide the same physiological action because you in fact have a pressure high and a pressure low with both modes.
  2. Instatewaiter

    Instatewaiter Octogenarian with a Cr of 3... send a troponin

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    Usually, Non-invasive positive pressure ventilation (NIPPV) is a term used to encompass ventilation without an endotracheal tube (ie both CPAP and Bipap).

    The term pressure support is really only used with an intubated patient. The term bipap is used if it is NIPPV. It is completely semantics but there are some minor differences.

    CPAP= PEEP for all intents and purposes

    Bipap ~ PS (except the way you talk about the numbers)

    In bipap 15/5 (ipap 15, epap 5) is the same as Pressure support of 10 with a PEEP of 5. So someone may say pressure support 10 and 5 and that is equivalent to bipap 15/5

    There is no difference between PS and bipap in terms of how most ventilators will deliver the PEEP + Pressure support (or in NIPPV, Ipap and epap). So to answer the question, there should be no major difference between your CPAP + PS (ie PS with PEEP) or bipap
  3. Paseo Del Norte

    Paseo Del Norte

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    That is what I intuitively think as well. There have been discussions regarding this where we work, basically on the lines of what to choose when a patient comes out of a hospital on BiPAP(tm). The ventilator is designed to provide both CPAP with PS and NIPPV (BiPAP tm) as non invasive modes (non-intubated). I see absolutely no physiological difference between the modes; however, it is strange that you would put two options out that are essentially analogues.

    I also see this in hospital ventilators such as the Servo-i. When I was in respiratory school, I was never able to get any good answers why we have two modes on a ventilator that are essentially the same? Now, I am not able to effectively explain to my fellow co-workers why this is apparently the case with our new ventilator. Basically, people are asking "why can't I just always use CPAP and just add PS if a patient comes out of the hospital on BiPAP?" I have no good answer at this point other than I see no problem with doing just that. The literature that comes with the ventilators essentially says that both modes do the same thing as well.

    I appreciate the response.
  4. Instatewaiter

    Instatewaiter Octogenarian with a Cr of 3... send a troponin

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    The only thing I could think of would be that the PEEP + PS setting has a backup rate and the bipap setting doesnt. But at least with the ventilators we use, you have to add the backup yourself.
  5. rrt

    rrt

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    Ok, When you have BiPap, you have 2 pressures working for you. IPAP and EPAP. You can have BiPap with a backup rate.

    When you use NIPPV, you have a Peep (EPAP), and Pressure Support (used during spontaneous breathing primarily) and a PIP or set inspiratory pressure. There is a difference between PS and PIP. During apnea, PS will not deliver a breath, PIP will. PS using a mask is misleading though. PS was developed to help overcome breathing through a ETT or TT.
  6. RT2MD

    RT2MD Wanna be Gas-passer

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    I'll throw out my opinion here, see if I can be of any assistance. Most of this was already covered in previous posts, but I figured I'd do my own take on it. My experience has been primarily with Draeger vents.

    CPAP + PS ---> This is a spontaneous, mostly weaning, mode for a patient with an artificial airway. When you are in this mode, the vent thinks you have an artificial airway in. If you use this mode in a non-invasive setting, you might have a very difficult time keeping your alarms from continuously going off.

    NIPPV ---> If you put the vent into NIPPV, you should be able to set your mode of ventilation anyway you could with an ETT or trach. The machine will be more forgiving of leaks, etc. You could set the vent up for PCV, with a set rate, or you could do CPAP+PS if you wanted to (or anything else, for that matter).

    Does that help address your question at all?
  7. Paseo Del Norte

    Paseo Del Norte

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    Thanks for the replies all. :thumbup: My question is more a matter of physiology. The thought experiment goes as follows:

    I have two patients that are exactly the same in all respects (impossible, I know).

    1) I put patient A into CPAP + PS at a setting of let's say PS +4 cmH2O above CPAP and CPAP of 4 cmH2O.

    2) I put patient B into NIPPV at a setting of IPAP 8 cmH2O and EPAP 4 cmH2O.

    All other settings (flow, etc) are the same.

    Then, I think to my self, will there be any physiological differences between these patients? In respiratory school, I was told yes; however, I cannot appreciate any difference assuming we set all the proper boundary conditions.
  8. RT2MD

    RT2MD Wanna be Gas-passer

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    Sorry, misunderstood the question. I think that clinically you would see no appreciable difference. The only theoretical change between the two would probably be dependent on the vent... Meaning that the flow patterns might be different... but I doubt there is any physiologic difference. The only difference is how the vent responds to leaks, etc.

    Also, I'm sure you already know this, but you probably need a mask without an exhalation port... since the bent has an exhalation valve.

    How were you told they differed in RT school?

    My $0.02...
  9. Paseo Del Norte

    Paseo Del Norte

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    Absolutely, "pure" ventilators unlike the Vision or the V60 are not particularly good about compensating for leaks. The physiological differences were not explained other than there is a difference. Sometimes, in school, it's best to simply let some things go... However, in practice, I like to appreciate some of these details.

    Thanks for the replies.
  10. RT2MD

    RT2MD Wanna be Gas-passer

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    I don't see any reason for there being any physiologic differences between the two scenarios that you described. If you really think about it, where would the difference come from? You stated that the pressures are the same, the flows are the same, both instances should be flow triggered/cycled and pressure limited. I think that you just didn't put enough faith in your initial evaluation!

    I hear you about the difference between school and clinical practice, though. I remember one time in RT school I was giving a case presentation to the underclassmen, who had just started and didn't know anything about vents yet - they had been introduced to CPAP, though. One of my slides had the ventilator settings on it, and I used it to walk through the terminology with the underclassmen... I said that PEEP was essentially the same thing as CPAP, just on a ventilator. One of my professors went off into this whole explanation of why that was wrong... I just let it go. :laugh:

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