In response to <lung dog>

If you are purchasing the Avea and a Nico seperately you would be negating the consolidated engineering of other current ventilator products. You discuss the evita being 10K more than the Avea but, you just equaled that with an Avea and a seperate NICO cost combined. You now have two devices to monitor and maintain instead of one system. As far as Siemens to Maquet it has now been three years since the transition, I guess time flies when you don't keep up with the marketplace. By the way I believe the Servo I has built in ETCO2, VCO2, and VTCO2 with their End Tidal system, mmmmm a built in NICO that is "plug and play" and movable from vent to vent, what a concept. You really should look at the marketplace a little closer before discussing it.

I think that they are forgetting to say that the AVEA has esopahgeal pressure. The AVEA would not be a much more complete equipment? Avea have TUBE COMPENSATION, APRV, ACTIVE VALVE, APRV, PRVC, PRVC with FLOW TERMINATION, SENSOR PROXIMAL, SENSOR DISTAL, MANEUVER CURVE PxV, ETC.ETC.

brandx>
Posted May 09, 2005 02:04 PM
Jeff,

Good discussion. Let me ask you this; what happens to the Autoflow algorithm with the Evita when the expiraotry flow sensor is deactivated?

My guess would be the ventilator works the exact same way without measuring return volumes.

Marcus


An answer for Marcus and Jeff.
This scenario presented itself a couple of months ago in our ICU.
Sick patient on A/C Vt 300 RR 24 PEEP 14 with peak pres ~40; decent ABGs with these settings.
Flow sensor inop alarm drives nightshift batty so one RT truns the flow sensor OFF. Result: patient desats, ABG drawn, CO2 increases from 55 to 95, 2 RTs busy in trauma room, resident speaks to staff Doc-tells him he hears less air entry-lo and behold a chest tube is prepared.
One RT (not the same that shut the sensor off) arrives at the bedside and notices the peak pressures lower not higher (good old residents and their chest tubes) turns on flow snsor and everything gradually returns to the previous levels.
Next morning, I used our seimens/drager sc9000 monitor as an external flow/pres transducer and was able to replicate and print the delivered VT changes when the flowsensor is shut off; the vent won't compensate for tubing compliance. Our patient was receiving ~205 cc instead of the 300.
Now as to why did the RT shut the sensor off? She was wrong but our 10 Evita 4s have driven us nuts with the flow sensor inop alarms over the last 5-6 years; we do use the fp730 with dual heated wire and we have been in a clmate controlled ICU for 3 years now. The company persistently and vehemently denied that this was a general concern with their vents. To finish, we just had their new heated exhalation block/flowsensor assembly installed in our vents and it has made a world of difference.

Costa
Montreal

quote:

Originally posted by CdnRT:
brandx>
Posted May 09, 2005 02:04 PM
Jeff,

Good discussion. Let me ask you this; what happens to the Autoflow algorithm with the Evita when the expiraotry flow sensor is deactivated?

My guess would be the ventilator works the exact same way without measuring return volumes.

Marcus


An answer for Marcus and Jeff.
This scenario presented itself a couple of months ago in our ICU.
Sick patient on A/C Vt 300 RR 24 PEEP 14 with peak pres ~40; decent ABGs with these settings.
Flow sensor inop alarm drives nightshift batty so one RT truns the flow sensor OFF. Result: patient desats, ABG drawn, CO2 increases from 55 to 95, 2 RTs busy in trauma room, resident speaks to staff Doc-tells him he hears less air entry-lo and behold a chest tube is prepared.
One RT (not the same that shut the sensor off) arrives at the bedside and notices the peak pressures lower not higher (good old residents and their chest tubes) turns on flow snsor and everything gradually returns to the previous levels.
Next morning, I used our seimens/drager sc9000 monitor as an external flow/pres transducer and was able to replicate and print the delivered VT changes when the flowsensor is shut off; the vent won't compensate for tubing compliance. Our patient was receiving ~205 cc instead of the 300.
Now as to why did the RT shut the sensor off? She was wrong but our 10 Evita 4s have driven us nuts with the flow sensor inop alarms over the last 5-6 years; we do use the fp730 with dual heated wire and we have been in a clmate controlled ICU for 3 years now. The company persistently and vehemently denied that this was a general concern with their vents. To finish, we just had their new heated exhalation block/flowsensor assembly installed in our vents and it has made a world of difference.

Costa
Montreal

I find the above situation puzzling (as a former Draeger educator I might add). When the flow sensor is removed the machine should revert to regular mode it was in but without the advantages of the AutoFlow, i.e the pressure curve would end up looking like conventional VC rather than PRVC. The Evitas have an inspiratory flow sensor (TSI) that is built into the machine. The machine will the deliver the set volume. Of course if there is a leak in the circuit, past the cuff, into chest drain, etc etc, there will be no compensation.
I am glad to hear the problems with the flowsensors have been resoved in some facilities. Occasionally I used to (covertly) suggest to end-users to buy their sensors from Envitec: they appeared to last a lot longer and were cheaper. ( And let me get some sleep at nights!!!)

I used to work with the Drager Evita 4 (E4)a few years ago. And now I work with PB 840.

I don't want to engage in vent extollation or bashing, just want to make sure I understand how the vents operate.

Please correct anything wrong in what is below.

The E4's flow sensor measures the exhaled volumes. Inside the vent is another sensor that measures volume leaving the ventilator.

When Autoflow is turned on the vent then adjusts all volume targeted breaths using floating Pressure Control. It looks at the volume returning to the ventilator and makes the adjustment. Turning on Leak Compensation should then compensate for any untoward effects such as a chest tube leak. This also automatically takes care of volume lost to tubing compliance, as the adjustment is made via returned volumes.

So if you have someoone in a volume mode (SIMV, CMV, MMV) with Autoflow on, then walk up and take out the flow sensor.

Does not the vent then revert back to flow controlled volume delivery? If one turns on the Pmax feature one could mimic PC's decelerating flow (one sets a pressure and insp. time, plus flow rate---when flow "bonks it head" on the pressure flow ramps down until volume delivered and/or time ends).

But you will now lose tubing compensation. With the PB 840 the tubing compensation is automatically added on the insp side even in flow controlled volume ventilation.

Is this a reason to always document both VTi and VTe on the Drager when using Autoflow in volume modes? (Or at least some average disparity?). That way if one is acutely forced to go to flow controlled volume mode (ala flow sensor removed) one could just increase the VT to compensate for tubing leak.

A couple other angles. In ARDSnet study, in any of the centers did the VT get adjusted for tubing compensation? With such low VT's, and with pressures kept low, one could surmise in adults this wouldn't perhaps make or break anything.

Also, the use of PRVC/Autoflow/VC type modes (and APRV) has recenlty been criticized as providing insufficient support when using ARDSnet protocol----as flow decays when the patient periodically pulls in more. (study at bottom). The sudy showed that traditional flow controlled ventiltion did a better job. In such a situation would not using Pmax then perhaps provide a better compromise? (Or at least deal with the cosmetics of a high Pip?).

Study showing VC maybe better than PRVC or APRV in terms of patient WOB,

Critical Care Medicine: Volume 32(12) Supplement December 2004 p A106
THE EFFECTS OF VENTILATOR MODE ON WORK OF BREATHING (WOB) DURING LUNG PROTECTIVE VENTILATION (LPV) IN ACUTE RESPIRATORY DISTRESS SYNDROME (ARDS): 382
Kallet, Richard H; Campbell, Andre R; Dicker, Rochelle; Mackersie, Robert C

Anesthesia/Critical Care, University of California, San Francisco at San Francisco General Hospital, San Francisco, CA; (Kallet)

Surgery, University of California, San Francisco at San Francisco General Hospital, San Francisco, CA (Campbell, Dicker, Mackersie)

Introduction:
Volume-control ventilation (VCV) is recommended for LPV but asynchrony is common.

Hypothesis:
Pressure-control ventilation (PCV), pressure-regulated volume-control (PRVC) and airway-pressure release ventilation (APRV) may improve asynchrony because the variable peak flow-rate (PFR) may reduce WOB. We tested if PCV, PRVC or APRV reduces patient WOB better than VCV with a PFR of 75 L/min.

Methods:
14 ARDS patients underwent a random mode presentation at a target VT of 6-7 mL/kg. Rate was held constant. Inspiratory time was 0.6-0.75 sec during VCV, PCV and PRVC. Peak pressure (PIP) was titrated in PCV and APRV to transiently achieve the target VT. In APRV, time at low pressure was set by the expiratory flow curve and the remainder of cycle time was dedicated to high pressure. Trigger sensitivity was 3 L/min. WOB, pressure-time product (PTP), central respiratory drive (P0.1), were measured with a BICORE monitor. Multiple comparisons were made by Friedmans test and Dunns test. Alpha was set at 0.05.

Results:
Compared to APRV, WOB and PTP were lower during VCV and PCV. End-tidal CO2 (41-42 mm Hg) and intrinsic PEEP (1.6-3.7 cm H2O) were not different.

Conclusions:
Pressure-regulated modes do not reduce WOB during LPV compared to VCV with a high PFR. We attribute this to a lower PFR that results when PIP is reduced to constrain VT delivery during assisted ventilation.

Jeff and others...

What if i told you that Autoflow targets inspiratory tidal volume in adults and taking the flow sensor out of line will not affect volume delivery. Expiratory tidal volumes are targeted in neonates with the Autoflow being implemented.

Also, the article you cited:

Critical Care Medicine: Volume 32(12) Supplement December 2004 p A106
THE EFFECTS OF VENTILATOR MODE ON WORK OF BREATHING (WOB) DURING LUNG PROTECTIVE VENTILATION (LPV) IN ACUTE RESPIRATORY DISTRESS SYNDROME (ARDS): 382
Kallet, Richard H; Campbell, Andre R; Dicker, Rochelle; Mackersie, Robert C

is bunk!! "Peak pressure (PIP) was titrated in PCV and APRV to transiently achieve the target VT". APRV is NOT set to achieve a tidal volume. Release volumes in APRV do not equate to conventional tidal volumes. The primary difference is that the release volume is passive, secondary to the elastic recoil of the lung and thorax.

The size of the release volume reflects the degree of recruitment sustained during the P High period and may include a portion of the inspiratory reserve volume.

Marcus

All good and fine, but why complicate things? As I said before: pull out the flow sensor from Evita and the machine reverts to a (non PR)VC without leak compensation. This was told to me by the former Evita 4 product manager, i.e. the person who actually designed the machine and presided over its development for several years.

hey wreckin , quit being so snippy. Are you all that?

Of the options listed I would choose the 7200.

I am surprised that no one has commented on the size of ventilators as being a factor. I always thought that as technology improved things got smaller...has anyone taken a look at the size of the Drager XL vs Servo i. The XL looks huge and seems extremely top heavy.