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PRVC vs. Autoflow
Granted the two are similiar, but Autoflow is not a specific mode, but rather a mode enhancement. It can be used with all volume modes, and is effective during the inspiratory phase. Autoflow converts a volume mode to a volume targeted, pressure limited mode. The goal is to deliver the set tidal at the lowest possible pressure (plateau pressure) utilizing a decelerating gas flow pattern. Autoflow allows the exhalation valve to behave as a CPAP valve (threshold resistor) allowing the patient to alter their flow patterns, enhancing the ability to breathe spontaneously. When autoflow is activated, a test breath is delivered at a pressure of 5 cmH20 above PEEP. The second breath is delivered at 75% of the set tidal volume. The third breath will be the set tidal volume, provided the pressure is 3 to 5 cmH20 below the pressure limit. The microprocessor algorithm then calculates the minimal pressure capable of achieving the targeted tidal volume. Autoflow recalculates compliance with each breath, and the next breath reflects any change in compliance. As the patients lung compliance changes, the pressure will adjust up or down in increments of no more than 3 cmH20 per breath. The benefits of implementing autoflow is a immediate reduction in peak airway pressure as a result of changing gas flow from constant to decelerating, thus lowering resistive element of airway pressure. During the inspiratory period the patient is able to exhale, cough or sigh.

Autoflow is haeds and shoulders above PRVC!!!!
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I suggest you re-evaluate your biased opinion of Autoflow. Siemens released PRVC 11+ years ago on the 300 series. It has been enhanced on the new Servo-i.
It amazes me to hear all these ventilator and modality comparisons.
The informed, professional RT at the bedside is the best technology a patient can hope for. It is obvious that RT directed weaning is more effective than MD directed weaning. Why? Not because of some fancy new mode but rather, weaning is a dynamic process requiring frequent intervention and adjustments.
Where do you work?
All the best.
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I agree with 'tinsley' in that you can have a ventilator with all the bells and whistles, but without a knowing clinician at the bedside you are not much better off. Drager has done a great job of marketing Autoflow as the solution to all your problems. But if you look beyond the surface of the E4, it really isn't that impressive. First of all it's a microcontroller, not a microprocessor. The response time reflects this in an independent study by Kacmarek and Dean Hess (Pressure Support and Pressure Assist/Control: Are There Differences? An Evaluation of the Newest Intensive Care Unit Ventilators; Respiratory Care. Oct. 2000) This also limits it's life as far as upgradability goes. I consider myself a fairly informed clinician and if I had to buy more ventilators today they would have to be the 840 without a doubt. There is just a higher level of sophisticaton in a much stonger platform. The two microprocessors make it extremely fast and will support many upgrades in the future. Add this to the fact that I feel that I have more control with the use of Rise Time % and Exp. Sensetivity. VC+ will be released soon, and I'm sure it will have it's uses as well. Drager seems to put out any and every mode/adjunct whether or not there is evidence that it will make a difference. As long as it sells I guess.
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NPB seems to put out any and every mode/adjunct whether or not there is evidence that it will make a difference. As long as it sells I guess, they get Bileve, VC+, Tube compensation now following Siemens and Drager. PAV is coming soon although not much physicans understand it.
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Sounds like ALL the ventilator companies, not just NPB, are "putting out" any and every mode/adjunct whether or not there is evidence that they make a difference. By the way, Siemens does not have TC or Bi-level on the SV300A. However, the new Servoi may have Bi-level soon if not already. I guess it's your decision as to whether or not you want to purchase or employ these software options.
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The informed RT at the bedside is the best technology a patient can hope for; however my bias towards Autoflow is warranted. Autoflow allows the patient to spontaneous breath during the inspiratory phase of the ventilatory cycle. Activating it allows for an open breathing system and promotes sponataneous breathing and affords the patient some comfort in an otherwise horrible situation; being intubated. I hate to inform you but the Servo-i offers no such breathing system:( Remember how important the informed RT is?:)

I work at the University of Maryland/Shock Trauma. How about you?
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I am glad you agree...if only for a moment.
I too am a fan of technology but it is of little value without skilled clinicians.
Please describe the breathing sytem on the Servo-i.
I was led to believe it is a dynamic system which allows free breating at anypoint and in any mode.
Any light you can shed on the subject would be appreciated.
Lions Gate, Vanc. BC
thanks for asking
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<Any RT>
I find your perception (which is common) of Autoflow interesting. A mode enhancement? Lets face it, if you look at any one breath, it is delivered with a Pressure based breath strategy, exactly like PCV or PS . And like PRVC the pressure target can vary from breath to breath to achieve the targeted set Vt. But unlike PRVC, Drager has the huge advantage of an active exhalation valve. I believe the Servo i now has this, as does the 840 (with VC+ apparently on the horizon). Another thing I find interesting is how some RT's are impressed with the reduction in Peak Press. with the use of Autoflow. First of all, ofcourse there will be a reduction in Peak Press. since PCV type breath usualy utilize lower flows (decelerating). And it has been a long time since I worried much about my Peak pressures anyway. The Plat. Press. and Vt are what are important to me. Anyone else have any thoughts on this?
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PRVC is Autoflow and Autoflow is PRVC....almost...

Autoflow on the Drager, with one behind the scenes click, changes the traditional SIMV and CMV volume breaths into PCV breaths which have variable Pi's per VT goal. PRVC on Servo just does the same thing ala a separate mode and is only available in A/C form.

There is the difference of which measured VT is used for Pi adjustment--that going out the vent or that returning. Each has advantages and potential problems. Would be interesting if clinician could select.

Drager has the "free" breathing valve, so the time setting of the PCV breath (SIMV & CMV volume targer now time at pressure) is, as stated above, such that a patient can breathe spontaneously.

Servo has a valve which is a stern gatekeeper and not a gracious doorman. But switching to Volume Support theroetically allows the patient to take over the breath while still getting flow friendly volume guaranteed breaths.

Problem with the Drager is that a long time spent at that high pressure may be like a fish being free to flop on the ground. Problem with the Servo's VS (PS varies for a volume target) is that the 5% peak flow termination critiera can have the patient either air trapping and/or actively cycling off the breath.

I don't know about any of you..but do you notice that there seems to be this mad rush to get each and every patient---almost no matter how sick--to be ASAP on the very least amount of ventilatory support possible? I call it the "Judeo-Christian Wean Ethic". The "he's on minimal ventilator support" seems to be a goal. I like to see the technology move forward. But sometimes I shake my head and think that "if the only options were an MA-1 (pre torturous IMV add-ons) and a T-tube this wouldn't be going on!".

To the Tune of "Let It Be" by the Beatles...

When I find myself in times of weaning trouble
Doctor Tobin comes to me
Speaking words of wisdom, "don't use IMV"
And in the hour of darkness
The patient is not in ecstasy
Setting a mode of wisdom
A volume would guarantee
Shout words of wisdom, don't use IMV

And when the broken organ people
Vented in the world agree,
There will be an answer, meanwhile don't use IMV.
For though they may be vented there is
Still a chance that they will someday be free
There will be an answer, don't use IMV.
Let me breath, let me breathe. Yeah
There will be an answer, don't use IMV.

And when the night is cloudy with secretions,
There is still a tidal volume that shines on me,
Shine on until tomorrow, let it be.
I wake up to the sound of an extubation
Dr. Manthous comes to me
Speaking words of wisdom, we let it be.
Let it be, let it be.
When the patient recovers he will breathe
Meanwhile, let it be, let it be,
Whisper words of wisdom, let it be.
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<Ed Fossas>
If you pick a patient who's peak pressure is constantly alarming and they are uncomfortable with the set flow rate in conventional decel flow volume ventilation then PRVC/AutoFlow can quiet the vent and the patient may be more comfortable. BUT if you use it on a patient with a high VE and high spontaneous flow rate then PRVC/AutoFlow will just make that patient work harder and look worse.
Like anything, you have to use it on the right patient. Consider PRVC/AutoFlow/VC+ another tool in your box to pull out when the right situation comes along.
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