A quick question: I used a Maquet Servo i vent to ventilate a patient and weaned her this morning. I wanted to use the Work of beathing index (W vent, W pt) to guide me in the process. Unfortunately, the W pt never posted anything else than 0, even with a pressure support under the Raw ext (the patient WAS indeed working hard).

As this happenned to anyone? What is the explination for this ?

Hey, Renton, we just got a new Servo i. Can you tell me about this WOB index. I can't find any information on it. What is normal? How do you use this info at your hosp.

It has been several months since I last used the Servo I. What a great little machine!

I was also curious about the WOBindex. I also found similar results to yourself.

Is you I equipped with NAVA. I can't imagine a more useful interface in theory, and without direct measurements of pressures I can't imagine in theory. I heard Dr. Christer Sidnerby present last year and I was excited to see it hit the market this fall.

Anyway these are useless ramblings and not really a response to your question.

The PAV function on 840 gives WOB indices as well and it offers a graphical representation of how much work the pt vs machine are doing. It is useful in weaning PAV but again not a direct measure of intrathoracic pressures.

The Avea also offers this data but with the use of Esophageal Pressure monitoring.

Like I said not really a response just ramblings

quote:

Originally posted by freadom:
Hey, Renton, we just got a new Servo i. Can you tell me about this WOB index. I can't find any information on it. What is normal? How do you use this info at your hosp.

From what I gathered, WOB indexes (vent and patient) could tell you about a combative patient, Raw or Cs changes or ever and unsuccessfull weaning. WOB vent over 2 would be problematic, and a WOB pt under 0.8 could indicate a successfull weaning (with appropriate settings of course).

1-I have been a RRT for a few years... I don't realy need a number to tell me that my patient is choking... And a unexperience RRT could rely to much on this value (which is kind of tricky to use);
2-With proper teaching this could be usefull in "undecisive" situation, in which a lot of theoricians failed to give us usefull evaluating tools (ie: P o.1 index, CROP, RSBI, and so on)

Still, I got no real answer from the community or sales rep. I will attend a seminar next week at Rosemont College (Montreal). A leader in WOB index will present. I will report the useful data...

quote:

Originally posted by FIN:
It has been several months since I last used the Servo I. What a great little machine!

I was also curious about the WOBindex. I also found similar results to yourself.

Is you I equipped with NAVA. I can't imagine a more useful interface in theory, and without direct measurements of pressures I can't imagine in theory. I heard Dr. Christer Sidnerby present last year and I was excited to see it hit the market this fall.

Anyway these are useless ramblings and not really a response to your question.

The PAV function on 840 gives WOB indices as well and it offers a graphical representation of how much work the pt vs machine are doing. It is useful in weaning PAV but again not a direct measure of intrathoracic pressures.

The Avea also offers this data but with the use of Esophageal Pressure monitoring.

Like I said not really a response just ramblings

To answer your question: no, it is not equiped with NAVA. I work in a community hospital, level 1 trauma, 4 ICU beds... we would have no real use for it. However, Sacré-Coeur hospital (level 3 trauma) should receive his in a few weeks (the first in the province to my knowledge). I supervise students there, and hopefully we will be able to test it on real patients.

I might be able to comment on the WOB index on the Servo I. I do not work with the Servo I very often but I used to sell 900C. The 900C had a lung mechanics calculater that measured WOB. I did not like to take the word of the engineers so I tested it at my old hospital to insure that it was accurate. True WOB is difficult because you have to get a constant flow and interrupt it to measure the pressure difference. We found the number to be quite accurate. We looked at the significance of this as it related to the ability to wean and found a nice correlation. All of this is anecdotal because there was no peer reviewed publication. It was submitted as an abstract. The problem lies in knowing normals and ranges. Hopefully, Maquet will do a better job of ecucation and enlighten us.

I finally got a good answer: Here's how to use W pt on a Maquet Servo i. The W pt is caculated only when a patient is on a spontaneous mode, and is calculated only at the begining of a cycle (start of inspiration). It also calculates P 0.1 at the same time. The W pt is only a reflection of how well your rise time and sensibility (trigger) is set. It does not reflect how well the patient tolerates weaning or is you have enough PS. So, if your trigger is to easy, you will get 0 W pt, if your trigger is at -17 (!), this value will go up. As I said before, the tolerated value is under 0.8 for W pt. Higher than that, you have to question yourself as of the pertinence of your setting of Rise Time and Trigger.

Now, I don't think that I really need a computer to tell me weather or not I installed a good trigger on a patient. However, for students (or inexperienced RRTs) that don't always grasp the subtilities of Rise time and sensibility, this could be of use.

Thanks to all who took the time to write or the read.

Thank you, Renton, for your reply. Your wisdom is appreciated.

Like you, we've gotten by just fine without knowing the wob pt., it's just nice to keep up on all this new data, at least I think so.

Thanks again.

quote:

It also calculates P 0.1 at the same time.

OK, a few more questions if you care to answer them.

What is P 0.1? What is the normal value? What does it tell me?

I'm also curious as to what the normal WOB vent is.

From my Hypoxic Drive Theory/CO2 retainer talk notes. Sorry for some redundancy.

P0.1 The Occlusion Pressure
Pressure drop first 1/10th sec. insp.
Before conscious perception or reaction can occur
Reliable measure of neural output.
Imagine what yours would be if you sprinted up two flights of stairs as fast as possible. Compare that with mild exertion or sitting on couch and watching TV (OK but not porn)

P0.1...index of neural drive, the pressure developed during an occlusion done during the first 10th of a second of inspiration. The P0.1 is the pressure measured in the first 1/10 of a second"”will call it the occlusion pressure for this talk.
The P0.1 in normal resting subjects is 0.75 cmH2O (Scon & Burki, 1990) and is highly correlated to the level of minute ventilation (Whitelaw, et al., 1975). In stable chronic lung disease the P100 ranges from 2.41-2.83 cmH2O (Scott & Burki, 1990). In patients recovering from acute respiratory failure P100 has been reported to range from 3.7 to 5.7 cmH2O (Montgomery, Holle, Neagley, Pierson & Schoene, 1987). Marini, J.J. (1988). Monitoring during mechanical ventilation. Clinics in Chest



Mouth occlusion pressure (P0.1)in acute respiratory failure. Herrera M Intensive Care Med. 1985;11(3):134-9P0.1 values over 4.2 associated with failure to become liberated from the ventilator.
78% of the time when "weaning" was successful"”P0.1 was 4.2 or less

P0.1/MIP relationship... fatigue setting in? For instance a ventilator patient on CPAP or T-tube for 2 hours...

Start of SBT P0.1 2.5 & MIP 68
End of SBT P0.1 5.6 & MIP 34

I recall when I worked with Drager Evita a few years back. The patient would be on supposedly support--but MD's tried to titrate ventilatory support ala sedation or paralysis---i.e. just above the failure threshold. SO they'd be on some pure PS setting. RR would be 28 and the patient just looked to me like they weren't getting enough support. I'd do the P0.1 measurement a few times and it' be from 4-5. I'd try to point this out to someone (ANYONE) and it'd be like shouting in an empty forest. So I'd either try to put the patient on CMV/Autoflow (akin to PRVC or VC+ on Servo and PB vents) and the patient would look markedly improved. But then, like a steady drumbeat, the mantra would pick up "why is he on CMV?!!" as if such a setting was a big step backwards on the Batann March ritual. Some nurses thought it was locking the patient out, as earlier Bear Vents the CMV mode locked out the patient. Soon the patient was returned to PS, or the docs never allowed me to even attempt the change. And inevitably the patient would just crash later.

If you have the P0.1 measurement you should use it, particularly during what is thought to be some full support mode---where actually just enough support is provided in bandaid fashion to mask the underlying fatigue.