To RT Kid-

If you think ATC does not add unknown pressure support to the circuit then how do you explain the higher PIP than your set PS and PEEP? If you will read your owners manual it will tell you that you will see a higher than set PIP due to the ATC being turned on. This extra pressure has to come from somewhere. That somewhere is your hidden PS from ATC. Don't just take what some sales rep tells you. Do your own experiments and start thinking outside the box.

That isn't the question. The question is how does the extra pressure measured by the ventilator translate when utilizing ATC?

The increase in pressure at the circuit Y is not pressure seen by the trachea or lungs. Much different than Pressure Support!!

In other words, an increase in the measured airway pressure is a normal consequence of ATC activation. The pressure increase is proximal to the artificial airway and is not pressure experienced by the lungs.

The increase in PIP you speak of is during mandatory breathes, new software by Draeger has the option for spontaneous breathes only thus negating this pressure that has been misunderstood.

With Pressure Support, if a patient generates a higher flow with a greater inspiratory effort, the pressure difference across the tube can be considerably greater than the set pressure support. Therefore, artificial airway resistance will not be fully compensated. If a smaller ETT is used, the pressure difference will beeven greater!! As patient's spontaneous efforts vary, pressure support cannot provide the adjustments needed for adequate and dynamic artifical airway compensation. ATC provides automatic pressure adjustments breath to breath in response to varying patient effort (flow). ATC adjusts the pressure proximal to the endotracheal tube in proportion to the flow, thus negating the pressure drop at the distal end of the artificial airway.

At least that is what we found in our lab!!!

And how does PS deal with expiratory resistance?

You still have not addressed the fact that even the owners manuel states you will see higher pressures and increased volumes when ATC is turned on.

Wow,
Just got on but it seems to me like someone is a Drager Rep???? Bashing the Servo-i? WOW. We are currently running 23 Servo-i's at our facility and are using them with great success in the adault and neo modes.
Poor neo performance? The Servo-i DOES NOT REQUIRE a proximal flow sensor (When we first looked at vents, we did a clinical trial with the drager and the flow sensor was a major problem - affected by secretions, etc..)
Insp and exp volumes are always wrong?
Servo is the only ventilator on the market that MEASURES inspiratory and expiratory volumes- not calculated. If anything, they are the most accurate.
ATC???? You have to be kidding... how much pressure support are you giving your babies when you "compensate" for their ET tube?? Tube compensation is built in to the Servo on a breath by breath basis, they just do not call it anything special.-well, they call it a good ventilator.
No room to breath during BiVent??? You can set PS at both High and Low pressure levels. We have had great success using bivent on Neo's (especially after recruiting the lung with Servo-i's Open Lung Tool.)
The Expiratory Cassette is expensive???? We have been running the Servo i now for 3 years and have yet to have to replace one (each of our vents came with 2) Lets not even get in to the price of your Drager flow sensor and how often you have to replace it. You think that delivering PS above the set pressure is dangerous? Wow. How long have you used the servo's bivent on an actual patient?
I love our Sero-i's and are thankful we went them.
By the way queen, where you aware that the hospital that Dr Habashi works at got rid of their Dragers and purchased Servo-i's???
Its good to do your homework.

btrdaddy,
looks like someone else needs to do their homework. If you review the discussions on this website or for that matter contact Dr. Habashi yourself you will find out that the Shock Trauma unit that Habashi heads up still has their Dragers. From what I gather it was a politacal battle at the hospital, but Habashi still has the Drager vents.

I would like to mention that I am NOT a Drager Rep, infact I Have experience with both The Drager and the Servoi and feel that both of them are great vents.

As far as the Drager vs. Servoi in the Neonatal world, I ask you this with such low flow rates and volumes where would it be best to monitor flow, at the wye or all the back at the vent? The Neonatal units that I know of that have the I's are not that happy with them in their units, due to this fact, but their adult counter parts love them. We have been using the Drager XL's in our neonatal units and have not had any problem with secretions in the sensor, sounds like you need to be monitoring them closer if a Neo is able to produce that much secretions befor you suction them. Also Stating that the Sevoi does not need the Flow sensor is kind of funny to me, because when you turn off the flow sensor on the Drager it looks at flow JUST like the Servoi, so when it is in, it is just that much better.

As far as the PS vs ATC on APRV. My personal opinion is that if the PS is set low enough that it is only overcoming the resistance of the ETT and not causing over infaltion of the alveoli at Phigh, then I don't see a real difference between the two. ATC is really just movable PS to overcome the resistance of the ETT. As flow increases or decreases the ATC will increase or decrease Pressures to match the RAW of the ETT. The one problem with setting a set PS level is that on some breaths the the PS will be to much and on others it will not be enough.

On the question of how much pressure support are you giving with ATC. You can't tell very easly when in a A/C mode due to the fact that the ETT is absorbing the pressure and it does not show up on your graphics the exact amount. The Hump on the pressure waveform caused by ATC is not being seen by the patient due to the ETT absorbing it. You can visualize it if you think about it. In conventional Square pressure breaths (PC, PRVC, APRV) the lungs are not seeing a true Square pressure wave form due to the fact that the first part of the pressure rise is being absorbed by the ETT. so the patient is actuallly seeing a accelerating pressure waveform when you take into account the RAW of the ETT. With ATC the vent increases the pressures at the WYE so that the patient is seeing a true Square wave form and does not experience the increased WOB associate with the ETT RAW.

As far as the Tube compensation being built into the Servoi itself is SALES TALK. Show me where on the pressure tacing the vent is compensating for Tube RAW!! How is it compensating for tube resistance when it does not know what size ETT is in place???? The vent compensates on a breath by breath basis for volume when in PRVC and that is it, FOR VOLUME changes not ETT RAW. Don't be taken in by sales talk ask for them to show you! I had a salesman try to tell me this too, but he could not tell me how it did it or prove it on the vent it self, SO IS IT TRUE?

Once again I would like to state that I personally feel that either vent is a fine vent and I like both, but lets not get into lies or misunderstandings on what one vent can or can not do.

This message has been edited. Last edited by: light,

quote:

The increase in pressure at the circuit Y is not pressure seen by the trachea or lungs. Much different than Pressure Support!!

In other words, an increase in the measured airway pressure is a normal consequence of ATC activation. The pressure increase is proximal to the artificial airway and is not pressure experienced by the lungs.

RT Kid, "the increse in pressure.... measured at your proximal airway sensor... is not pressure experienced by the lung"?
I was just curious about this (pretty interesting actually)
If the pressure proximal to the airway is say 30cm/H2O... and you say the pressure in the lung is different.... say 25cm/H2O... I was just wondering how this works.. doesn't pressure equillibrate? If your airway sensor is reading 30 then what exactly is the pressure in the lung? Isn't this important?
I am honestly just curious. Like I said earlier, we are a happy Servo-i house and have never had issue with tube compensation. (what happens when the internal diameter decreases inside of the ET tube over time due to secretion build up? Does ATC automatically adjust for this change in resistance???)
Queen, I would like to say that I did not want to come across harsh I just do not like that you had a "list" of things you did not like about Servo... sounds like you work for Drager and that you are not an actual consumer. (sounds like oldtimer is a servo rep by the way)
The original question was asked by some one who wanted to know which vent was the best.. everyone has their opinions. My sugestion is to get the vents in your facility and do a clinical trial on each of them (kick the tires). Look for ease of use, pre-use check, down time between patients, patient interaction. Get your biomed department involved (let them open the vents up and look at the technology). Have the nursing staff give their opinions... Its not really what WE like, its what YOU like and what would work best at your facility. (Word on the street about Habachi's hospital by the way.. just thought that was interesting that hospital that the main physician for Drager works at has changed their fleet to Servo)?????
You work for Ddrager Queen, is this true?

Light, very well put. You have to be careful about what sales people tell you and what the vent can actually due. We went Servo (and again, I am glad that we did) not because of what the rep told us, but because we did our own personal trial. I did come accross an article by the way that showed trigger sensitivity and volume measurements to be more acurate with the servo compared to vents that require flow sensors. I can send it to you if you would like to provide me your email address. It was an interesting read... so I agree, you have to go with facts, not what the rep says. I am not here to bash Drager (we were using the Evita 2 for a long time in our Open Heart Unit) Anyway, thanks for your unbiased input in this matter. They may end up loving the Drager or Loving the Servo.. again, kick the tires

btrdaddy,
IF you just post where I can find the article (Journal, date, name of article ect) I would like to look at it. We tested in our lab with a seperate monitor and compared its readings of flow at volume and the drager was right on.
Your question of proximal airway pressures and lung pressures can be answered this way. If you were in VC and your PIP was 30 and your Ppl was 20 you would deduce that the RAW is causing the pressure difference. RAW formula = (PIP- Ppl)/flow in L/sec. When you are in PC and flow is maximized (decelerating to baseline) your PIP and Ppl should be relatively the same. What you do not see on the waveform (because it is looking at what is being delivered, not what is actually happening in the lungs)is that the pressure at the end of the ETT for the first part of the breath is lower than the pressure at the top of the ETT. You can see this by placing and pressure monitor on the end of a ETT between the wye and the test lung. I know that this is a crude example, but it proves a point. We have also placed a tube in a Pig lung in the segmental bronchi and hooked the tube to a pressure monitor to look at the pressures seen their compared to the PIP and the Ppl. The pressure actually decreases more and more as the the airways become smaller and smaller.
The Ppl is the pressure seen at the end of the ETT and the PIP is pressure seen at the top of the ETT, but in PC we do not see this pressure difference on the monitor, but it is still there due to the RAW of the ETT.

Hi Light,
Pediatric Critical Care Med 2000 Vol. 1, No. 2
This was pre servo i but comapred the SV300 to the Babylog (WOBp. Like I said, just an interesting read.

PS: Articale name
"Comparison of work of breath between two neonal ventilators utilizing a neonatal pig model"
Mark J. Heulitt, MD; Ronald Sanders, MD; Shirley J. Holt RRT, Stacy M. Rodes, BS; Tracy L. Thurman, BS.

Hope this helps.. please let me know what you think.