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Ahmad

NAVA mode of ventilation in Servo i

Have you heard about NAVA

Is a mode of ventilation that available on SERVO I ventilator, delivers assist in proportion to and in synchrony with the patient's effort as reflected by Edi signal (the electrical activity of the diaphragm)

since the diaphragm is the main respiratory muscle so they use the its electrical signal to trigger spontaneous breath from the ventilator, which lead to better synchrony between the patient and the ventilator, also decrease WOB.

NAVA using special feeding tube carrying 10 electrodes, this tube goes down to the stomach so it can be used for feeding also it picks the signal from the diaphragm and send it to the ventilator.

Potential benefits of NAVA:
Improve synchrony
Decrease WOB
Prevent over or under supporting of the patient (the patient will determine the amount of PS)
NAVA works independent of leakage (Neural triggering not flow or pressure) so it is excellent with neonate and small babies

Any body have experience with NAVA can share us his information ??

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AhmadPermalink Reply by Ahmad on May 6, 2009 at 4:15pm
Yes Alfonso,
Hiccups may trigger the ventilator and cause a short assist delivery. may trigger the ventilator and cause a short assist delivery.
Regarding seizure i have not enough information, i'll check again
Ahmed.I.FouadPermalink Reply by Ahmed.I.Fouad on May 21, 2009 at 10:05am
I do not understand the way the ventilator should be triggered by the patient on NAVA.

DO you have an answer for this?
AhmadPermalink Reply by Ahmad on May 22, 2009 at 4:49pm
AHMED

Thank you for your interest

As you know, the respiratory center in the brain sends signals through the phrenic nerve to the diaphragm (Edi signal), the diaphragm will contract causing -ve pressure in the chest which moves the air in,
in case of conventional ventilation all ventilators will respond to the patient's effort after it sens the -ve pressure or reverse in flow (bias flow) this means the response takes place after the diaphragmatic contraction, and that will lead to asynchrony.
in case of NAVA ventilation, the machine able to pick the signal which sent to the diaphragm (Edi signal) and start working at the same time with the patient's diaphragm, this means synchrony. they are working together

the ventilator will uses the magnitude of this Edi to determine the amount of PS to be delivered. so the patient will has the choice to increase/decrease the PS ---TV delivered by the machine by in increasing/decreasing his/her inspiratory effort, so patients will lead the machine and wean them selves



i already explained how servo i can get the signal, you can review it
HajiHPermalink Reply by HajiH on May 24, 2009 at 10:29pm
i wonder if the patient has hiccups, would that be a problem?
AhmadPermalink Reply by Ahmad on May 25, 2009 at 1:21pm
As hiccups are involuntary contraction of the diaphragm it might trigger the ventilator and cause a short assist delivery, but this not only in NAVA this also in all modes.

Hiccups one of the reasons that lead to auto triggering, but, in the other hand, NAVA solved another reason of auto triggering which is (leak), NAVA is working independent of leak
Howard McDonaldPermalink Reply by Howard McDonald on July 11, 2009 at 10:20pm
Nazir BurkiPermalink Reply by Nazir Burki on July 13, 2009 at 3:06pm
I had been in presentation on NAVA. It looks good. i dont know if it can be used in Apnea confirmation test?
Howard McDonaldPermalink Reply by Howard McDonald on July 29, 2009 at 4:34am
When the catheter is in place and no signal is shown from the brain it has been shown as a double check with EEG
Tanveer Abbas KhanPermalink Reply by Tanveer Abbas Khan on July 13, 2009 at 7:07pm
But how we will determine the driving pressures in this MODE?
AhmadPermalink Reply by Ahmad on July 13, 2009 at 8:14pm
I have no information about NAVA with Apnea test,, But regarding inspiratory pressure setting:

Mr. Khan, in NAVA you do not have to set a certain pressure. because your patient is going to determine the amount of PS that he/she needs. HOW??

In NAVA you set (NAVA LEVEL, cmH2O/micro volt) which is the amount of PS for each one micro volt comming from the brain.
or the amount of PS in proportion to the patient's effort.

If you set NAVA level of 1for example, and your patient wanted to take a sigh his/here brain will send a high signal lets say 18 micro volt then the ventilator will respond and give him/here PS of 18 cmH2O. in the next breath if your patient wanted to take a small breath then his/here brain will send a small signal lets say 5 micro volt, then the ventilator will give him/here PS of 5 cmH2O.
Marwan A AlhazmiPermalink Reply by Marwan A Alhazmi on July 21, 2009 at 4:59am
I was introduced to the NAVA concept during my course as a theory. I once met with a representative from Maquet few months ago during the Society of Respiratory Care in idaho. There are a lot of question marks that Maquet representative couldn't clear up, I don't know if it was due to his lack of knowledge about the mechanism or the insufficiencies of the mode itself. One of the major questions he couldn't clarify was whether if the brain signal is standalone effective measure to determine the force of diaphragmatic contraction, as the contraction of the muscle occurs with the calcium influx and the activation of sodium-potassium pump in order to generate ATP. He couldn't clarify exactly if the changes happen to the Tidal Volume and WOB during difference Dz states is neurological or physiological, in other words is it all represented in the Action Potential or not ?
Also another claim that it can over-come sedation and muscular blockade agents... It is true (theoretically) in both pre and post-synaptic muscular blockade agents. But how can it overcome sedation that actually cause a Respiratory Center Depression at the Medulla level such as opioids and sedatives (isn't the whole signal is going to get affected,depressed or at least confused?? !! )

I really like the way it sounds, I just hope it is not one of those new corporate tricks to improve sales ! I really wish an RCT or at least a pilot will be done on this to compare it with a controlled group and see how it really works in the real world, not Alice Land.

Thanx Ahmed for the great topic :)
AntonioPermalink Reply by Antonio on August 3, 2009 at 8:57pm
Hello All,

I have had some experiences with NAVA that I would like to share. First Marwan is correct regarding the chain of events that occur when the action potential is occurring for the diaphragm. What NAVA mode capitalizes on is the EMG of the diaphragm and the specialized ng picks up the sodium-potassium pump changes during the depolarization of the muscle and sends the timing and magnitude of the signal to the ventilator at the same time. The interesting thing about this technology is that there are no claims with regard to overcoming sedation but rather a lot of discussion about how sedation and pain management during mechanical ventilation can be assisted to provide better utilization of the medications and maintain spontaneous breathing.

The signal that is captured from the ng to the ventilator is called the EDI signal and for the researchers in the world they label it Eadi. It stands for electrical activity of the diaphragm. The rationale for the edi helping clinicians understand loading of the muscle is actually quite simple. When variables cause elastic or resistive forces to increase it becomes more difficult to inflate the lungs. Remember that the lungs do not inflate themselves so the signal is a great indicator for changes in lung elasticity, compliance and resistive properties. So when a patient is developing atelectasis gradually over time or the have fluid in the lungs they will show a gradual increase in the edi signal. The human body is the world's best ICU in my opinion. Yes we have to help it from time to time but it has it's own ventilator (diaphragm and accessory muscles) its own blood gas machine that makes changes to tidal volume, rate, HCO3 levels based on metabolic needs and disease state.

No one knows whether NAVA will be the end all be all but it does provide us the opportunity to optimize the things that we have evidence to increasing time on mechanical ventilation. Asynchrony, over support (VILI), undersupport (atelectrauma), sedative effect all have a negative effects on patients.

The most interesting thing about NAVA is the Edi signal in my opinion because its addictive. There are too many things to try to explain in one blurb but the one that won me over was a patient that was triggering effectively and seemed to be weaning but would never tolerate sbt. Upon placement of the edi catheter we saw that the patient was triggering with accessory muscles but no diaphragm activity. This was compelling because typically this patient would get a trach and end up long term on mechanical ventilation. We set the support level to get the diaphragm to be activated and weaned the patient more effectively because we had an objective measure of the workload of the patient throughout various phases of their weaning.

Paralytics - no good for Edi or NAVA. I agree that manufacturer's have done a lot in the past to promote a technology but in essence they are trying to create something better that hopefully will show benefit and improve sales.

I don't beat them up like I used to but I do beat them up on over selling. I think that this takes pulmonary to another level and I believe this edi signal and eventually nava is here to stay. Physiology and mechanical ventilation working as one, who would have imagined.

Be well.

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