NAVA

Multi-disciplinary experience of NAVAat the University Hospital of Bordeaux

No. 22

2 | Critical Care News

Consistently ranked among the top three French reference medical centers, the Bordeaux University Hospital (Centre Hospitalíer Universitaíre de Bordeaux or CHU Bordeaux) is comprised of a cluster of three main hospital sites and admitted over 134,000 patients in 2009 to its 3100 hospital beds for medical and surgical treatments.

The institution was one of the very first in France to implement NAVA – Neurally Adjusted Ventilatory Assist in 2008, and is now utilizing this ventilation technology in multiple intensive care units. These intensive care departments also took initiative in arranging and sharing their experience with NAVA at the first French Annual NAVA Symposium earlier this year.

Multi-disciplinary experience of NAVA at the University Hospital of Bordeaux

Professor Olivier Brissaud and colleague examine NAVA and Edi settings on an infant patient in the NICU/PICU

Critical Care News | 3

“We have had experience of over 60 patients with NAVA in the past two years. In the beginning of our experience we used NAVA for 30 or 60 minute intervals, to observe and learn and to be familiar with it, but in time we have had some specific patients on NAVA for over a week or more.”

“We now consider NAVA to be a routine ventilation mode. Every week we have at least one or two patients on NAVA. However we are selective; we don’t place an Edi catheter on patients that are expected to be extubated within hours, but on the

“In terms of lung protective ventilation, you strive for as low pressures as possible in the pulmonary arteries. In the past, these patients were sedated and given muscle relaxants for many days, so it was a long recovery. Currently the trend is to put the patient on assisted modes as soon as possible to promote spontaneous breathing. So there was Pressure Support, but now with NAVA there seems to be a good strategy for a post-operative course with fast-tracking. Our objective is to try to wake up the patient as soon as possible to wean and extubate”.

Critical Care News met with staff members of the Cardiothoracic ICU, the Thoracic Surgery and Abdominal Surgery ICUs, the Neonatal and Pediatric ICU and the Medical ICU at the Bordeaux University Hospital to hear about their experiences with the clinical application of NAVA in specific patient categories, and heard about the plan for implementation of NAVA in the Neuro ICU in the near future. Members of various intensive care departments also discussed their plans for the use of non-invasive NAVA, and future research within the area of NAVA and Edi monitoring.

Dr Philippe Mauriat is chief of the Pediatric Cardiosurgical ICU from Department of Anesthesia and Critical Care 2 (Dr Alexandre Ouattara). Dr Mauriat was formerly chief of pediatric intensive care at a hospital in Paris, prior to joining the Bordeaux University Hospital in 2008. He describes the scope and size of the operations within his ICU:

“We treat neonates, infants, children and adults with congenital heart disease. Since the 70’s the surgeries have expanded in these indications and increased with excellent results. For the average patient population, it is necessary to perform repeat surgery, for example switching valves and pacemakers in growing children as well as older adults. The term is GUSH – Growing Up Heart disease. We now have a population of pediatrics and adults as well as neonates. So for me it was very interesting to try NAVA, for the neonates, children and adults”.

NAVA as protective ventilation in cardiac surgery patients

Dr Mauriat first heard of NAVA in 2004 from Jennifer Beck and Christer Sinderby, who were guest-lecturers in Paris. He describes the factors that led him to be interested in implementing NAVA in the cardiosurgical ICU: “In cardiac surgery patients, we are primarily interested in protective ventilation and less invasive and less aggressive therapies.”

Use of NAVA in Cardiosurgical ICU patients

Dr Philippe Mauriat took the first hospital initiative to use NAVA in the Cardiosurgical ICU, and has been using it since 2008


patients where we think there will be a more challenging recovery process.”

Edi monitoring of cardiosurgery patients – in conventional ventilation, in NAVA, and after extubation

Dr Mauriat describes Edi monitoring as a fascinating and a very interesting new aspect of treatment and diagnosis of cardiosurgical ICU patients: “For the first time we now have monitoring capabilities of the diaphragmatic activity. We have seen some patients just before extubation who have a very nice Edi signal, and once the endotracheal tube is removed their Edi signal is increasing, indicating that the patient is getting fatigued, and might need reintubation or another support. In patients where we see some edema in the larynx, for example, we can observe the change of the Edi waveform. If the patient is becoming fatigued, we try first to give support in the form of non-invasive

ventilation, and if that does not help enough, we reintubate. I am waiting for the new NIV NAVA. It is very promising and I hope to work with it”.

Monitoring sedation levels in postop cardiac surgery with the help of Edi signals

Dr Mauriat also believes that the Edi signal may be valuable to be able to detect the level of sedation, and to minimize the level of sedation: “We frequently cannot switch the patient to Pressure Support ventilation since he is still heavily sedated, and where we are unsure why switching is difficult and why the patient does not respond to Pressure Support. However, the Edi signal gives the opportunity to observe diaphragmatic activity and the return of the diaphragmatic signal for activity of breathing. If you look at the Edi signal and it is very low, you can try to reduce the level of

sedation to increase the Edi signal.”

“We are making a study with our nurses about the sedation level. In this study we will adapt the sedation by means of the Edi signal and the pain scale; they have a scale to see if the patient has pain, but don’t have a scale to see if the patient is too heavily sedated. But now we can monitor the sedation level and the return of spontaneous breathing with the Edi signal.”

“The idea is to titrate the sedation level according to the Edi signal. And when the patient has a strong Edi signal, then you can switch to NAVA.”

Comparing Edi signals in conventional mechanical ventilation to NAVA

Dr Mauriat regularly monitors Edi in conventional mechanical ventilation modes, such as Pressure Support, before switching over to NAVA. He shares his

Colleague of Dr Mauriat and Cardiosurgical ICU infant patient on NAVA


them work a lot from the beginning, you start out with a little work and you can check their work of breathing and load or unload the diaphragm with adjusting the NAVA level.”

“We find that NAVA is useful in some patients without any diaphragm muscles at all, so we must retrain the diaphragm and condition and recover the respiratory muscles. We all have a big interest in NAVA in our unit, but especially our physiotherapists, since they have been working for rehabilitation of the diaphragm for many years, but had no way of seeing the effect of what they were doing. Now you can see a bedside parameter with the help of Edi monitoring.”

Dr Mauriat has had several patient cases where Edi signals provided information that he was not expecting to see. He explains: “We have one case on video of a patient with low Edi signal, in contrast to other patients. This patient had diaphragmatic paralysis on one side; we used x-ray and echo to confirm the diagnosis, and performed a procedure to stretch the diaphragm and after that the Edi behavior was very different. The

experience: “Of course, we see when the Edi signal comes back in sedation washout; it is one of the most interesting aspects of any mode of ventilation. It is very interesting to see the change of the Edi signals. And with NAVA, it is interesting to see the Edi signal and that NAVA respond to the patient effort and demand. We think it is very important to compare the Edi signal in conventional ventilation and in NAVA – Edi monitoring is not only valuable for NAVA – and it is especially interesting to monitor Edi after extubation, to see the diaphragmatic activity of the patient. The patient’s Edi signal helps us in conventional modes, once we have strong Edi signals we switch to NAVA, since NAVA is better for the patient post-operatively.”

“Some of our patients have been on ECMO for two weeks, and have had muscle relaxants during this time with no diaphragmatic signal, and we lost the patient diaphragmatic activity and the diaphragm muscle. Also on these patients, as soon as we see a small Edi signal return, we switch to NAVA to force the patient to work, to train the diaphragm and for rehabilitation of the diaphragm. , You don’t make

cupola was very different, it was not moving before, and after surgery we had an Edi signal so we could extubate.”

Current experience with NAVA in France, and treatment opportunities for the future

Dr Mauriat was the primary initiative taker for the first French NAVA user symposium earlier this year, and explains why he identified the need for the activity: “I work with different national scientific societies, but sometimes it is necessary to push something new as an initiative. As many intensive care units within the Bordeaux University Hospital were gaining experience with NAVA, and as I had already lectured about NAVA at some national congresses, I saw an opportunity to bring together experiences of NAVA from many different intensive care units in France. Personally, I believe that NAVA is part of the future in intensive care”.

“We should start to define groups of patients in intensive care that might benefit most from NAVA. With the specific category of pediatric cardiac surgery patients, NAVA is very interesting since it is a protective form of ventilation; it protects the heart and gives faster weaning. In the future it might be interesting to put more types of patients on NAVA for weaning, as a standard procedure. From general experience in the surgical ICU, like cardiac surgery or after neuro surgery, there are very few indicators when you may safely extubate the patient and be comfortable that he will tolerate extubation. Edi signals provide a good indicator parameter to monitor and show that the patient is ready to wean, or to be extubated. It is important to make more clinical studies to define the groups of patients that might benefit the most.”

“Personally, I think that sedation levels and titration with NAVA and Edi monitoring is a main point of interest, from a physiological perspective. To me, NAVA and Edi monitoring are only the beginning of the story of a new physiological approach to mechanical ventilation.”

Dr Mauriat displays an infant NAVA patient case on video with ventilator screen values


Professor Olivier Brissaud is the chief of the pediatric and neonatal intensive care unit at the University Hospital of Bordeaux, and has been working in that capacity since 2005. He briefly describes the current situation in the department: “We have 18 beds, for mixed pediatric and neonatal care. We usually have 6 or 7 children and 11 or 12 neonates in the unit, and over the past year we had 550 patients in total, and it is 50/50 mix of pediatrics and neonates. It is very interesting to have this kind of unit, since we have a dynamic and challenging situation, but very rewarding. It can be difficult to treat contrasting patients, such as an 800 gram neonate to older children with other types of challenges, a big contrast but very interesting.”

“When we ventilate neonates it is always Pressure Control ventilation that we use, but it depends on the patient population and pathology too. Usually we use Pressure Control in neonates and Volume Control in older children, since they have different pathologies, especially bronchial pathologies. We used to use Volume Control in all the children but the ventilators are very adaptive now, and one thing we want to increase is spontaneous breathing. In my opinion, I think it will be a real benefit for children and neonates to use NAVA in invasive or non-invasive ventilation. It is a big challenge and this new kind of ventilation pushes us to learn and to do more. For earlier weaning, if we go directly to NAVA ventilation, it is a possibility for us to go faster and opens doors for us.”

Recent implementation of NAVA in the neonatal/pediatric ICU

Professor Brissaud first heard of NAVA about 3-4 years ago at a national ICU congress in France, at the pediatric session, but he just recently started using NAVA. He explains: “In pediatric and neonatal ICUs, we have a lot of technology associated with ventilation, monitoring, sepsis monitoring and we have to select carefully. I am one of

those doctors who always said that if you know Pressure Control and Volume Control and assisted ventilation very well, you can make it work in nearly 100% of children and neonates. But I think this was before NAVA”.

“We have had NAVA on five or six children in the past two months, and I can say that this is a very good experience so far.. It has been very easy to use, also easy to see the Edi signal. Our experience is small so far, the experience of Philippe Mauriat is different since he has been using NAVA for 1 or 2 years, and it is easier for a cardiologist to use new technologies since there is a higher homogeneity in that patient category.”

“For us it is different in this respect, we have neonates and children, from 500 grams to 80 kg, and we have to adapt ourselves all the time, But the first feeling I have is it is easy to use, and we have some benefits to using NAVA. For example, we can more closely observe the physiopathology of breathing in patients, which is very important for us. We can look at the patient to see if he is able to breathe or not, we can also look

at the assistance of the ventilation, to observe if we give too much or too little support. The first step of our experience with NAVA means that we are in the observation phase, and we can capture some new information in our practice”.

NAVA and Edi monitoring from a 950 gram neonate to pediatric patients The recent experience of NAVA for Professor Brissaud ranges from a neonatal patient to 2 year old patients. He describes the experience so far: “The smallest patient on NAVA was 950 gram, and NAVA worked well in this patient. Another benefit that we must always ask ourselves is if we are giving the right level of sedation, and Edi monitoring with NAVA can help us in this respect. When we look at the Edi curve and there is no signal, we must ask ourselves, if the sedation can be minimized in this particular baby. For this reason, it is interesting for our practice to look at the ability of children to have diaphragmatic contractions and activity. We have not observed Edi signals in patients that have been extubated yet, but this is also an interesting area to look at the Edi signals. We will be monitoring Edi signals after extubation in the future, maybe in the baby that has been on NAVA, so that we can see before and after. It can help us to observe if the baby is getting stronger or not, or to avoid intubation.”

Non-invasive ventilation and NAVA in neonates and pediatrics

Professor Brissaud states that non-invasive ventilation and NAVA is also a very interesting future direction, in his opinion, in neonates and in children. He looks forward to gaining experience with NIV NAVA, and explains why: “The real problem with non-invasive ventilation in my opinion is always in patients between 6 months old and 7 years old. After that it is easy to do NIV, since older children, can communicate more easily and can be managed better with masks, and so

Gaining experience with NAVA in the neonatal and pediatric ICU

Professor Olivier Brissaud


maybe NAVA is a good alternative or a way perhaps to use less sedation”

Learning about NAVA and Edi monitoring technology in the NICU/PICU

Professor Brissaud emphasizes that all the physicians on the unit have tried and experienced and are familiar with NAVA and Edi monitoring. “There is a parallel to EKG technology – it existed when a few users tried to do something new and different, and when it works well, it is difficult for others to go another way. It is important that more people experience the start of something new”, he says

“In terms of NAVA level, we look at the patient, and we look at Edi tracing first in conventional mode and in the NAVA preview screen. We try to adapt the NAVA level individually for each patient situation. For some babies it was a NAVA level of 2, for some 3.6, it depends on the condition. It is important to look at the Edi signal, and if we think that the assistance to the baby is too high when we observe the Edi signal, we have to try to make a decrease in assistance, and look at the signal and see how it is affected. For NAVA level, we look at the Edi signal in a conventional ventilation mode and make an adaptation thereafter. It seems to vary from baby to baby, but it is an individual physiological approach.”

on. Below 6 months it is easy, since we have technology for NIV in neonatology, there has been development in this area for a long time, and when we have a young baby, below 6 months it is easy to use NIV. Between the ages of 6 months and 7 years we have lots of problems with the interfaces, we use a lot of masks, different kinds, and they are not adapted, and the helmets are not very easy to use in small children, and one of our problems in addition to the interfaces is the ability of the children to be synchronized and it is a very big problem. The young children between 1-7 years are too young for adult modes in synchronization and spirometry, and too old to use what we use in neonatology, for example the spirometry sensor at the nose of the children, close to the tube, since it is a good way to reduce the time between the patient requirement and the ability of the machine to deliver the breath. So in neonatology it is quite common to insert this sensor at this place, but if we do it in older children, there is a lot of auto triggering, since children are too old for this position of the sensor, and it is difficult for us to use the flow as a trigger in this respect. We have to find something more physiological and in this way Edi monitoring can really help us in NIV. Our objective is really to develop non-invasive ventilation in this patient population between ages 1 and 7, and if NAVA can help us with this, it would be a great benefit.

“We have to try a new technology and, if we want progress with it, we have to choose a specific population of patients to develop our experience. We have to make choices. With children, it is difficult to wean and get them off the ventilator. Of course, if we have a better synchrony between patient and the ventilator, the tolerability will be better. But we need to gain experience in this in order to prove the theory, which is very seductive and interesting. We have to gain practice, and I think it will be a benefit to patients during weaning, since it may make a close adaptation between the ventilation and spontaneous breathing of the patient. For example, we observed a a young baby in Pressure Support ventilation, , and we saw that he was very uncomfortable and

agitated. Our first strategy was to make some adaptations in the ventilation and modification of the settings, but it did not help, the baby remained agitated, and we saw that the baby was not so synchronized to the ventilator. We decided to try NAVA and it was our first experience. We were very surprised to see that the baby suddenly became very calm and comfortable. We were very surprised in this first case, and we want to gain more experience to confirm these first surprising experiences. The third experience we had with NAVA was with a baby in the unit that was difficult to wean. The first answer to the problem during the night was to introduce sedation and it worked, the baby stopped spontaneous breathing, and for the doctor on call that night, I think that he went on the easier course, and said it was very difficult, and the baby was agitated, and modifications did not work, so I used Sufentanyl. This is a rather common situation, especially at night, but a loss of time for the baby and us in regard to the weaning process to spontaneous breathing. In this example we asked ourselves if NAVA was an alternative. I think that we should try NAVA as an alternative to sedation - a more physiological philosophy to treatment. Sedation is good in some specific circumstances, in patients with very difficult pathologies, to make ventilation and maybe in some patients, the solution is not to sedate or to sedate less, and

Professor Brissaud and staff members with infant patient on NAVA


Future potential for NAVA in neonates and pediatrics, in clinical and practical perspectives

Professor Brissaud sees several opportunities for potential benefits of NAVA in the ICU in future. “First of all, I think that this technology will help us to look at sedation. We must choose the most synchronized ventilation for the patient, and we must encourage spontaneous breathing of the patient. We have to ask ourselves about sedation and in this respect I think that NAVA may be very helpful to us. Secondly, I think in non-invasive ventilation in babies and small children, it will be very interesting to use NAVA, maybe even more so than invasive ventilation. The synchronization is very important in NIV, and to be synchronized early in the process is very interesting and to be non-invasively ventilated as early as possible. In general I think that we want to become more non-invasive practitioners; if we pull the tube earlier, or use NIV and avoid the tube altogether, or use NIV in very premature babies with artificial surfactant –all the practitioners would like to find solutions to make the installation of surfactant without intubation. Today I am aware of some units that use gastric tubes to insert to the lung and to administer surfactant, instead of a chest tube. We would like to make ventilation without chest tubes whenever possible. With NAVA in this respect, I think that we can push ourselves in this direction, and open the door.”

“We have a baby on the unit on NAVA today that was born at 36 weeks of gestation, with pneumothorax. The baby was born two days ago and he received artificial surfactant, and developed alex syndrome on the left side, we inserted a tube into the lung and last night the attending physician gave a high level of sedation to the patient, since he was agitated. This morning we decided to start NAVA to decrease the sedation, and to see the Edi signal for this baby and to see if it is possible to extubate earlier. After a few hours on NAVA he seems to be doing well. The other end of this reflection is if we can limit the hospital stay just one day, it is equal to 4,000 Euros in expense, so this is very important”, says Professor Brissaud.

Dr Boulard is head of the neurosurgical ICU of Bordeaux University Hospital, where he has worked 40 years. He briefly describes the department: “Actually they are 2 separate neurosurgical ICUs of 12 beds each which should merge into one unit of 24 in about 3-4 years. In our neuro-surgical unit we take care of patients from conventional neuro-surgery, such as tumors and hemorrhages, and the specific pathology which is severe meningeal hemorrhage.”

Dr Boulard has encountered earlier revolutions in neuro intensive care during his long career. He explains: “I have been working in this field all my life. I started here in 1973 in the children’s hospital, the same year I got my degree in anesthesiology and intensive care. At this time we were only few people, maybe 50. The first ICU for neuro-surgery was created here in 1968, and when I began in neuro-surgery a few years later, it was forbidden to give one gram of sodium to the patients. We were talking about acute hyponatremy and water intoxication which were killing patients and I didn’t understand anything. After some time, I asked why it was forbidden and colleague suggested me to read some books written by Bernard Weil but after reading I still didn’t understand. My colleagues and I thought that we were doing things the wrong way. I asked the head of the department and he gives me permission to administer sodium as a different therapy but with caution. So I began to give 1 gram of Sodium in 500 ml of glucose solution. Nothing happened. After some days I put 2 grams and nothing happened. After some weeks we saw our patients with normal sodium value in blood. Now in contrast the dogma is sodium, sodium, sodium,… we were pioneers and I would like my doctors to be a little more curious and creative today, not too much, but a little more.”

With the background of this pioneering spirit in neuro intensive care, Dr Boulard

is very excited about the opportunities that NAVA may provide, when it is implemented in the neuro ICU later this year. He explains: “NAVA seems to be very interesting because one of the difficulties after coma is respiratory concerns with the effects of a prolonged artificial ventilation and a weak diaphragmatic muscle. It’s like when you break a leg and put it in plaster. When you take out the plaster, the leg has lost 2 to 3 kg of muscle. It’s the same with the diaphragm. In addition it could also be another central problem on patient with acute brain pathology and often metabolic or functional disorders which can affect respiratory center and delay the respiration recovery. So we usually do weaning by switching from control to spontaneous ventilation, sometimes with non invasive ventilation, but we are always downhill from the problem which is more central. NAVA gives a solution because it works with the phrenic signal and gives a reflection of the recovering respiratory center. This is why it seems that neurologic post-coma patients can be good subjects for NAVA because it uses what the respiratory center can still deliver. We will observe this in the coming months”.

Preparing to implement NAVA in the Bordeaux University Hospital neurosurgical ICU

Dr Boulard


Professor Castaing is chief of the Medical ICU in Bordeaux University Hospital, and started working there in 1975. He was named Professor at the same institution in 1992. The medical ICU currently consists of 4 professors, 4 full time resident doctors, 4 senior intensivists, and 8 interns, and approximately 100 critical care nurses. They manage care for a total of 32 ICU beds and 20 sub-acute beds.

Before working in the ICU, his focus was on physiology, and later on physiopathology and mostly respiratory physiopathology. His focus has influenced other members of the ICU staff. He explains: “In 1982, I went to work for many months in the lab of Professor West in San Diego. This is why about 50 % of the staff in this unit work in respiratory physiopathology, like Gilles Hilbert and Frederic Vargas who continue what I began many years ago.”

The medical ICU had some similar challenges that were shared with other ICUs across the world last year. Professor Castaing says: “We were affected by the swine flu epidemic, even if we didn’t have to treat many patients; we had about 10 of which 2 needed ECMO. We had recently renovated part of our ICU, and 2 patient rooms are equipped with air locked infection controlled rooms for immunodepressed or contagious patients. With swine flu, patients in those rooms were put on negative pressure.” From his long base of experience, Professor Castaing also shares what he sees as the challenges of intensive care in the coming years and the need for more advances in technology, like NAVA: “I think we will have to define what we can do because we have more and older patients in the ICUs in Europe and administration is reducing number of beds which force us to make some choices. Our society will maybe have to accept that patients shouldn’t always die in ICU. French recent law of 2006 allows now staff in ICU to limit resuscitation procedures to

some patients with co-morbidities and there is no single day where we don’t discuss some cases which mean there is a problem that we will have to solve in the future. It’s a problem which is more acute today than when I begin to work in ICU. We spend much more time with family today to prepare them and to explain what and why we are doing in terms of providing care to patients.”

Conventional ventilation therapies and challenges with non-invasive ventilation in the medical ICU

Professor Gilles Hilbert of the medical ICU describes the conventional therapies used in the medical ICU:”The two main conventional modes we use today are Volume Control, and Volume Support, followed by Pressure Support. We do a lot of non-invasive ventilation in the ICU, so we optimize the settings in Pressure Support for non-invasive ventilation, which is a challenge for us.”

Professor Frédéric Vargas of the medical ICU describes the typical mix of patients and clinical situations in the medical ICU and the focus on non-invasive ventilation in the unit: “We

have all types of patients, but primarily acute respiratory failure, complex COPD patients, and hypoxemic respiratory failure in immunosuppressed patients. Our team has published on the topic of immunosuppressed patients and acute respiratory failure; it is one of the areas of research we are most interested in.

We have a challenge, in the prognosis of immunosuppressed patients who are hematological, as soon as the patients improve, we try to switch to non-invasive ventilation, but above all our main objective is to avoid intubation. The lower the rate of intubation, the higher the rate of survival is in these patients, and if we really must intubate, we try to extubate as soon as possible to avoid complications.”

Professor Gilles Hilbert outlines the patient categories that are of particular interest for non-invasive ventilation in the unit: “We use non-invasive ventilation in all types of acute respiratory failure, but above all in COPD patients, because the level of contamination is very high, but also in patients with pneumonia, or ARDS, if the level of the contamination is very low. As recently as 3 or 4 years ago, there was a French consensus on how

Experiences with NAVA in the Bordeaux University Hospital medical ICU

Professor Castaing


How NAVA came to be implemented in the Medical ICU

Professor Hilbert describes the events leading to the implementation of NAVA: “We worked with the staff of Laurent Brochard during one year, including an evaluation of how to test modes, how to obtain Edi signals, how to set the NAVA level, when it was brand new in France.” Dr Vargas adds: “In our team, we were the very first NAVA user in France. We work together in the respiratory team; I’ve tested it on myself. In the beginning we put the NAVA on less complex patients to see how to obtain Edi signals and to position the Edi catheter. The next step was to understand the treatment and how to understand the Edi signals of what diaphragmatic activity is indicating. In the first patient we wanted to understand how it worked, about the algorithm and how to optimize the settings. What is very interesting in NAVA is that you only have one setting, which is the NAVA level, compared to other modes with many settings.”

Experience with NAVA and interest for non-invasive NAVA

Professor Vargas describes how the unit is using NAVA and some of the scope of their experiences with it: “We saw that when we titrate the NAVA level from a low level to a high level, at certain times when you see a plateau in the Edi, pressure and volumes, we look at the patient, see how he is reacting to the setting modification, and with our objective in frequency and tidal volumes you usually obtain the correct settings where you do not over- nor underassist with NAVA.”

“We have treated between 50 and 100 patients in NAVA in invasive ventilation, but we do not have experience yet in non-invasive NAVA. The types of patients that we most commonly treated with NAVA are primarily stable patients with weaning problems, including COPD etc. In these patients, we also monitor Edi signals immediately after extubation as we want to prevent reintubation. We have recently heard about the possibility of monitoring Edi signals in levels of sedation, and we

after extubation who develop ARF after extubation, and the study by Esteban demonstrated a higher mort rate in the group of patients with NIV. Even if the skills of the team using NIV were not sufficient, many teams use NIV only for one year, and a high level of many years experience and skills is needed in using NIV in this patient category. This is an important point as the results were disappointing, as it was the first time that the use of NIV was associated with worse outcomes. The idea of our team was to start a randomized controlled study where Frédéric Vargas is the main investigator, to use NIV in patients with criteria of severity.”

Professor Vargas describes the study: “This includes patients older than 55, and cardiac pathology with respiratory disease. One of the specificities of management is NIV, the sequential mode used but not continuously, discontinued support as a mode to support COPD patients, and we apply this mode in all types of ARF. We have a protocol in a study published in 2001 in these types of immunosuppressed patients.”

to manage the patient on non-invasive ventilation and pneumonia and ARDS. The data today on hypoxemic respiratory failure, and three years ago I discussed this point in a debate with the master Laurent Brochard, indicates that different strategies depend on the different types of patients. For the immunosuppressed patient if you cannot improve ventilation after several hours, then you must see if you can do more, without intubation; once you intubate the patient there are at risk. For patients with hypoxemia without immunosuppression, there is not really an indication for non-invasive ventilation, but with well trained staff, like in this ICU, we try NIV but if the situation does not improve within 2-4 hours, we reconsider which strategy we will use.”

Professor Hilbert describes a particularly challenging situation in regard to non-invasive ventilation, and a randomized controlled study that is planned: “Non-invasive ventilation after extubation is really a challenge. Two large studies, by Keenan et al, and Esteban et al, demonstrated no advantage to using non-invasive ventilation in patients

Professor Frederic Vargas


are also interested in investigating this indication when we receive more data.”

General current opinions of NAVA in the Medical ICU

Professor Vargas shared that generally extubation occurs about 24 hours after placement of the Edi catheter and treatment with NAVA, and that the Edi catheter is usually kept in place for 48 hours post extubation, to monitor activity of the diaphragm. He stated that he and his colleagues are interested to compare the Edi activity under Pressure Support in the same routine and method. He says”We find NAVA to be very interesting, especially as we know now that conventional mechanical ventilation modes are not optimal for all patients, referring to the scientific literature, where it is reported that 25% of patients show asynchrony in Pressure Support or assist control ventilation. These asynchronies lead to an increase of duration of ventilation. In non-invasive

Professor Hilbert and Professor Vargas with staff members

ventilation, we know from the literature that 40% of patients have a high ratio of asynchrony.” Professor Hilbert concurs: “Asynchrony in NIV is one of the factors, but we know that interface and leakage, are other important factors. Now that we have NIV modes on ICU ventilators, it has improved the situation a lot, for care of the patient that is already in NIV. In terms of asynchrony, NAVA is interesting in the perspective of invasive and non-invasive ventilation. “

What is foreseen as the future for NAVA in the medical intensive care unit

Both Professor Vargas and Professor Hilbert see needs and opportunities with NAVA in the future. Professor Vargas shares: “We need to have clinical studies for NAVA in non-invasive and invasive ventilation. We are planning a multi-center study about NAVA in France, where Bordeaux will participate for invasive ventilation in weaning and NAVA, with a large group of patients, and we also need studies for non-invasive ventilation. Today we have performed a physiological study, and we hope to increase these studies to document the benefits of NAVA.”

Professor Hilbert believes that they will be treating more types of patients with NAVA and NIV NAVA in future: “Yes, at this time we will stick to clinical studies but in future there will probably be more patients treated. But for now we try to match clinical activity to clinical studies. There are certainly more types of patients who should benefit from NAVA. If we were asked the question, what could be improved on NAVA from a development perspective, we really could not answer that. Many years ago there was a lot of work and trials on EMG and spectral activity to indicate fatigue of the diaphragm. At that time, some people including L Brochard, were looking at those specific areas of the spectral signal, but it was invasive and needed data. Now we have the Edi catheter, so we can see the diaphragm of the patient more clearly, and have even more in depth monitoring opportunities in the future.”

Professor Gilles Hilbert


Dr Hadrien Rozé is working on the thoracic intensive care unit as well as the abdominal intensive care unit from Department of Anesthesia and Critical Care 2 at the Bordeaux university hospital, and became interested in using NAVA after seeing the experiences of his colleague Dr Philippe Mauriat in the cardio surgery ICU. He states that they used it very slowly to begin with, to see how to manage the settings and become familiar to find the right way to use NAVA. He describes the situation in which NAVA was implemented: “In the thoracic ICU we have 10 beds, and we also have a unit for patients with abdominal disease and surgery, so there are 12 beds there. We have 3 ventilators with NAVA, and everyone is familiar with the system throughout the department, since everyone is on call at least one night a week, they are familiar with it and do not change the settings. In the thoracic ICU, we have very specific patients: transplantation, very sick thoracic surgery, very sick COPD patients that have surgery, emphysema, surgery in the bronchus, for tumors and so on. In this situation the weaning is very difficult. It was nice to start NAVA in these patients, who frequently are very difficult to ventilate in Pressure Support with pneumatic triggering, there can be lots of failure. Pressure Support is our standard mode of conventional ventilation in the ICU” says Dr Rozé.

“My first experience with NAVA was about a year ago. First I had to see how I should use it, and then show it to the rest of the staff and the physiotherapists. During the night shift, if the physician is not used to NAVA he will change it to something he is familiar with. I didn’t really know in the beginning how to set the NAVA level, so I needed to study and think about this in the beginning. Lots of data, seeing what happened during procedures like thorascopies, or in other care situations with the patient. We wanted to see how NAVA was working in these different circumstances during the day”, explains Dr Rozé.

Determining the NAVA level – a method evaluated in over 40 patients

During his experiences with NAVA, Dr Rozé has developed a method to determine the NAVA level in his patients. He describes the background and procedure as such: “I was convinced that using the same pressures as the patient had in Pressure Support in the NAVA preview screen was not the right way to use it, since we don’t know if the level of pressure we use in Pressure Support is truly adaptive to the individual patient need. So we looked for another way to start with NAVA, at the right level that was truly adaptive to the individual patient. So we have evaluated over 40 patients right now, including a very severe ECMO patient over the course of last winter, who suffered from the swine flu influenza, so with very long periods of controlled ventilation, very weakened patients. We had 4 patients on ECMO devices, transplants and other reasons, very sick, with severe ARF, so we knew it would be hard to wean them from

mechanical ventilation, it was better to use a new system of ventilation with these very sick patients, since we can see by the Edi signals immediately if the ventilation is adaptive to them or not.”

“After 55 days of mechanical ventilation, you can imagine the atrophy and weakened state of the patient, sometimes it takes days to help them to strengthen their respiratory muscles. The same is valid for diaphragmatic paralysis patients, since we have to use another muscle. It may take weeks to wean from Pressure Support. What I like about NAVA is that we can use it as a way to adapt the pressure to the strength of the patient, and the Edi signal is a very good tool to show us where we are going, and which level of pressure to use according to the patient needs.”

Doctor Rozé states that the way he sets the NAVA level is not volumetric. He says: “With NAVA we just see how much electricity the patient is able to generate without Pressure Support, and

Working with NAVA in the intensive care units for thoracic surgery and abdominal surgery

Dr Hadrien Rozé


then we help him to be under this limit, to condition him. We check the patient every day for the maximum of Edi he is able to generate without Pressure Support, and then we adapt this NAVA level in order to be under this value. We want the patient to have support, but not too much, so it is a good way to adapt the pressure to the patient so he will use his diaphragmatic muscles properly.”

Monitoring the Edi signals in conventional modes, in NAVA and after weaning from prolonged periods of mechanical ventilation

Dr Rozé feels that there are multiple ways in which monitoring Edi signals are of value. He says, “In the beginning I used the screen on patients with Pressure Support and looked at intrinsic PEEP, in order to see the data between start of Edi signal and the start of the pneumatic trigger, and set the right level of PEEP to have synchronization between Pressure Support and the start of the signal. Even if we stay in Pressure Support, we use the Edi signal to improve the way we are using Pressure Support. With Edi monitoring,

we can see if there is a delay between the start of the Edi signal and the start of the pressure delivery. We trend the data for all of our patients, and most are able to breathe normally after weaning and extubation. One patient had to be reintubated, and in this patient we monitored and recorded the Edi signal. He had intermittent non-invasive Pressure Support, and we could see the variation of the Edi signal, in Pressure Support and non-invasive and in between, and when he had fatigue, we could see this on his Edi signal.”

“I can say that the Edi signal was decreasing before increase of respiratory frequency, or even acidosis so it was interesting that the signal was the first clinical sign of respiratory distress”, adds Dr Rozé.

Dr Rozé says that in general patients are on about 19 days of mechanical ventilation with Volume Control, and then are switched to Pressure Support for one hour, just to see how the patient is tolerating Pressure Support. Thereafter the patient is switched from Pressure Support to NAVA. They are typically on NAVA for 6 days for weaning, prior to extubation.

Edi monitoring can reveal patient information that the doctor would not otherwise be aware of

Dr Rozé has had a number of interesting patient cases, where Edi signals revealed more than he would have known otherwise. He explains: “I had one case of a patient with a lung that was surgically removed due to cancer. He had a brain stimulator for Parkinson’s disease, and we were not sure how it was affecting him, or if it was working. When I started NAVA, it did not work at all, since the stimulator was recording. So we could not use NAVA since the brain stimulator was active. We knew that the brain stimulator was working, and I tried NAVA during one night, we did not see how the muscle was contracting, but it was possible to use it without any trouble. The shape of the signal was almost the same as other patients; I thought there would be two waves, but for this patient that was not the case”.

“We also had thoracoplasty for a patient with very severe tuberculosis, we removed the ribs and tried to ventilate but there was decompression with just a part of the lung that was working. We did not have any problem with NAVA with this patient either. NAVA is nice to try out with these types of patients with very different respiratory physiology – one lung or two lungs, but the diaphragm seems to work naturally anyway”.

Patient case report with Cystic Fibrosis, lung transplant and NAVA, recently published in the British Journal of Anesthesia

Dr Rozé frequently encounters a situation probably familiar to most ICUs that treat cystic fibrosis patients: once they arrive in the ICU, they are ventilated with non-invasive Pressure Support and are very familiar with it and using it 23 hours a day, with maybe only one break a day when they are at end stage awaiting transplantation. He describes the situational risks: “When we absolutely have to intubate them, sometimes the patient can die within 15 minutes, since we simply have no way to ventilate them – pressures are difficult and it is too late, their lungs

Dr Rozé is researching and evaluating methods to establish NAVA level in thoracic patients


this patient, but I really wanted to show in this case how we are using the NAVA level. The way we use it is very simple and it is described in that case report.

We used NAVA and titrated the NAVA level in the same manner in another patient, who was very severely ill, and had undergone ECMO for 55 days. We had very good results of using NAVA in this patient, to slowly regain his diaphragmatic muscle strength and function again”.

Education of staff members from both ICU departments

As familiarity with NAVA has grown, and Dr Rozé has gained knowledge, he has been able to share it with staff members in both the thoracic surgery ICU and the abdominal surgery ICU departments. “Sometimes they call me to look and adjust levels, but I am not always there, and since the patients are here for a long time, everyone must be familiar with NAVA and use it. In the beginning, I would arrive in the morning and they would have switched from NAVA to Pressure Support during the night?, but after training with all of the staff, with Edi catheter placement and NAVA levels, now all 15 physicians are trained. They were all very interested to learn. We now even receive contacts

Developing research and awareness of NAVA for the future

Dr Roze has a number of ideas for use of NAVA in future situations. He outlines some of the areas he is most interested in: “We want to use NAVA non-invasively, for cystic fibrosis patients that are not intubated and have non-invasive ventilation all the time. They have nasogastric tubes since we need to feed them to supplement their nutrition, so for these patients, who are in physiotherapy, it will be a good start. The physiotherapists with these patients are very interested in NAVA, as a course of treatment prior to transplantation.”

“Most of our patients that need lung surgery have emphysema and COPD, and with the surgery and thoracotomy post-operatively, they have trouble to breathe. For non-invasive ventilation there are two studies showing it will reduce mortality in these patients, one is hematological and the other is in post-op thoracic surgery. Another way to introduce something other than Pressure Support after thoracic surgery for treatment of acute respiratory failure after thoracic surgery, using non-invasive ventilation will reduce mortality, so this is a very interesting area for us to examine the use of NAVA.”

“In the cystic fibrosis case published in the BJA, there was a challenge to ventilate

are too diseased. We do anything to avoid this situation – and if this happens and the situation improves, we wait for transplant; we have an emergency list for allocation of lung transplants. Even if a donor for transplant becomes available, we often must wait 4 or 5 days, and I try to stop mechanical ventilation with Volume Control ventilation since I don’t want to stay too long without using the diaphragmatic muscle. It is very difficult to use Pressure Support in these patients, once they have been intubated and mechanically ventilated on Volume Control.”

“The case in the British Journal of Anesthesia was the first case of cystic fibrosis we had on NAVA, but these patients are very difficult to ventilate, and this case was a good example of what we can do with NAVA when Pressure Support fails. I tried everything, as described in this case report, and since the patient was awake and very familiar with Pressure Support, we decided to use NAVA without protocol, and the patient was ventilated with NAVA the patient could say if she was comfortable or not. I was satisfied with her blood gases, intrinsic PEEP, everything was working but the first endpoint was the patient comfort, for her it was possible to stay on NAVA for 4 days until we had a suitable lung donor. After the transplant surgery, the Edi catheter was in place, so I used NAVA for a few hours to compare before and after, everything has changed after surgery – compliance and resistance and so on, with Edi monitoring. With this patient, the compliance was low and resistance was high with high intrinsic PEEP, it was easy to believe that the Edi synchronization would lead to a completely different situation, which was the case. It was interesting to note the maximum electricity the patient was able to deliver every day, which I tested with a Edi signal test with 7 cm H2O Pressure Support every morning to see the max Edi the patient was able to do. This max level was increasing every day, the endpoint was to have muscle strength and improve it, since she was intubated for 9 days. By successively increasing Edi peak every day, we could see when to decrease the NAVA level and strengthen the diaphragm.”

12 µV20 µV

Mechanical ventilation during NAVA ventilation before and after lung transplantation. From the top to the bottom, peak pressure (Ppeak) time curve, flow time curve, volume time curve, and Edi in microvolts. Note the different scales of each curve between pre- and post-transplantation as published in the British Journal of Anesthesia


References

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2) Jaber S, Petrof BJ, Jung B, Chanques G, Berthet JP, Rabuel C, Bouyabrine H, Courouble P, Koechlin C, Sebbane M, Similowski T, Scheuermann V, Mebazaa A, Capdevila X, Mornet D, Mercier J, Lecampagne A, Philips A, Matecki S. Rapidly Progessive Diaphragmatic Weakness and Injury During Mechanical Ventilation in Humans. Am J Respir Crit Care Med 2010; Sept 2: PMID 20813887

3) Rozé H, Janvier G, Quattara A. Cystic fribrosis patient awaiting lung transplantation ventilated with neurally adjusted ventilatory assist. Br J Anaesth. 2010; 105(1): 97-99

4) Coisei Y, Chanques G, Jung B, Constantin JM, Capdevila X, Matecki S, Grasso S, Jaber S. Neurally Adjusted Ventilatory Assist in Critically Ill Postoperative Patients: A Crossover Randomized Study. Anesthesiology 2010 (Sept 3) PMID 20823760.

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from other departments; maybe if they have a patient that fails Pressure Support or has respiratory distress, they call me sometimes to see if NAVA would be of use after weaning failure. Since most of our patients are typically on mechanical ventilation a very long time, and are complex, we start NAVA from the first day, but some of the patients in abdominal surgery may return to surgery, and when they ask me to use NAVA it is almost always

after failure of Pressure Support, not as a first-line ventilation therapy in these patients”, explains Dr Rozé.

Dr Roze summarizes the familiarity of the procedure with NAVA for both groups: “The staff members in thoracic ICU and abdominal ICU are trained and are using NAVA. When you start to use NAVA the second day with a single breath test, the patient may not tolerate that at all, just check the maximum of what they are

able to do. If you look at the trends, you can see before the single breath test and after, and after I want to see stepwise increases every day after the first single breath test. The physiotherapists are very important to the development of the patient, and they like NAVA very much, and are involved in the treatment. A small team, but everyone has a clinical task and we all work together. Everybody is a NAVA believer at bedside.”

http://www.ncbi.nlm.nih.gov/pubmed/10581089



















CRITICAL CARE NEWS is published by MAQUET Critical Care.MAQUET Critical Care AB171 54 Solna, SwedenPhone: +46 (0)8 730 73 00 www.maquet.com

©MAQUET Critical Care 2010. All rights reserved. Publisher: Martin LöfbomEditor-in-chief: Kris RydholmrÖverby is Rydholm ÖverbyOrder No. MX-0840Printed in Sweden

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