Vol. 19 • Issue 2 • Page 28
Neurally adjusted ventilatory assist is an exciting, new, progressive technology available to health care professionals who provide ventilator management to the neonatal population. Although it is a Food and Drug Administration-approved therapy, practical experience and data in this area are lacking. Therefore, a carefully prepared and organized plan is essential so that implementation is successful.
Two Ohio hospitals recently collaborated to bring NAVA ventilation into their neonatal intensive care units. Toledo Children’s Hospital began using NAVA in May 2008, soon after it became available. Akron Children’s Hospital followed suit approximately a year later.
This article shares our combined experiences in initiating NAVA in our NICUs and presents the best of both processes in an effort to benefit other NICUs.
Clinicians must consider many issues when bringing a new modality such as NAVA into a NICU. Many items promote the success of NAVA’s introduction, including physician support and understanding, possible observation of a NICU with established NAVA use, and expert support at the bedside for the preliminary initiation of the mode. Additional items such as education, patient selection, appropriate physician orders, and bedside charting are other key points to emphasize.
Learning from others
NAVA is currently a novel concept to most users. Attendance at a NAVA symposium may be beneficial for NAVA proponents before initiating the technology in the NICU. These symposia are located throughout the country and may be sponsored by the manufacturer, hosted by respiratory therapy societies, or presented by hospital education departments. The content of these symposia includes the basics of NAVA and the current clinical literature.
A limited number of NICUs are utilizing NAVA on a consistent basis. Most of these departments welcome visiting staff to observe and learn about a patient on NAVA. These visits allow the opportunity to speak directly to the physicians, respiratory therapists, and nurses who have hands-on experience with NAVA.
Pre-implementation education
“Key trainers” or “super users” are essential in assisting with the education process. These personnel should be educators or informal leaders in the NICU. A packet of educational materials should be organized for each key trainer to provide consistent information for staff training.
Suggested items to include in this packet are articles describing the theory of NAVA, excerpts from the operating manual, setup guide, clinical management tips, charting procedures (See Table 1), and pre/post tests.1,2After preparing key trainers, the process for educating the staff can occur in conjunction with clinical representatives from the company. This should be done within a brief timeframe so the actual initiation of NAVA can take place readily after education is completed. New terminology may need to be reviewed multiple times.2(See Table 2.)
When ready to place the first patient on NAVA in the NICU, it is advantageous to have experienced NICU NAVA “users” available at the bedside. Although clinical application specialists from the company are usually available and recommended, the presence of a NICU health care provider (neonatologist, neonatal nurse practitioner, or RT) who has used NAVA in the clinical setting is optimal. This health care provider can guide patient selection, application suggestions, and continuing education throughout the day.
As Toledo Children’s Hospital was one of the earliest users, access to a clinical expert was not possible, and the first few patients ventilated on NAVA caused some stressful situations for the staff. However, the experience at Akron Children’s Hospital included an expert at the bedside for the initial application on a patient. The experience that expert brought to the bedside was reassuring for all staff members and helped to decrease anxiety levels.
Selecting the first patients
It is suggested that patients initially placed on NAVA are those with the highest likelihood of success. Infants > 30 weeks with respiratory distress syndrome who have a good respiratory drive and minimal apnea are ideal candidates. These infants have ample reserve and will do well regardless of the mode of ventilation. Starting with these infants will allow the new user to develop a level of comfort with NAVA and minimize any perceived risk to the infant.
As long as NAVA is used in the FDA-approved manner, Institutional Review Board (IRB) approval should not be required for its use in the NICU. Of our two institutions, one facility chose to go through the IRB process in order to follow the infants and collect data. The other chose not to do this as data were not being collected. Either way is acceptable.
In both NICUs, we spent time talking to the parents of infants selected to be on NAVA. We explained that NAVA is a new mode of ventilation that gives control to the infant and that the ventilator functions only augment the infant’s spontaneous respiratory drive.
Initial physician orders
One of the initial challenges faced when first using NAVA in the NICU is helping the physicians understand and use the new terminology in a consistent manner. We found that preprinted orders guided and prompted the physicians to settings that need to be considered and ordered to place a patient on NAVA. Orders should be modified as needed for use in specific NICUs.
It is also suggested to have reference materials for quick guidance. A setup guide could be located near the patient’s bedside or in charting materials for easy access during initial setup. Operating manuals can be accessed for further information. Visit www.advanceweb.com/respiratory to see a preprinted order sheet and setup guide.
Charting
Charting procedures will need to be addressed with both respiratory and nursing personnel. Because the mode has new terminology and different measured values from other modes, new areas will need to be created for documenting. The variability in Edi signal results in a significant breath-to-breath variation in both pressures and rate so charting an isolated number, as is currently done with conventional ventilation, has little value.
To obtain meaningful data, it is important to look at the trend graphs for the past hour and report either an average value or range for each parameter. Table 1 shows an example of the new parameters that need to be recorded in the chart.
Clinical management tips
Our combined experience with the use of NAVA in the NICU over the past 18 months with more than 120 patients has made us aware of a number of clinical tips, some of which are in the manufacturer’s pocket guide, which may be useful for the novice user:22. The Edi signal in the neonate is variable.There can be significant breath-to-breath variability in peak pressures and respiratory rate. Although the user manual shows uniform Edi tracings with predictable responses to interventions, the neonate’s response is more erratic in the short term. Use the trend monitor to look for changes over time and do not depend on breath-to-breath responses.
2. During placement of the Edi catheter, the most important component is the EKG progression. It is essential to see the largest p-waves and QRS complex in the upper lead and the absence of the p-wave and a small QRS complex in the lower leads. At times, the superimposed blue color of the Edi signal will drift from the middle two leads to the upper or lower leads. If the EKG progression is appropriate, this color drift does not seem to impact NAVA’s effectiveness.
3. A large p-wave or QRS complex in the upper and lower leads but a smaller EKG signal in the middle two leads suggests that the Edi catheter has most likely coiled in the esophagus and should be removed and reinserted.
4. When choosing the NAVA level, the company recommends matching the pressure estimate curve to the pressure curve as close and as often as possible. After numerous applications, we learned the starting NAVA level can vary because the neonate will adjust the Edi signal intensity to deliver the required pressure. If the Edi peak is consistently high
(> 15-20 microvolts), increase the NAVA level to “unload” the neonate and allow the ventilator to do more of the work of breathing. Conversely, if the Edi peak is consistently low, decrease the NAVA level to reduce the contribution of the ventilator and allow the neonate to do more of the work of breathing. We recommend using increments of 0.5 to adjust the NAVA level.
5. Apnea is typically defined as no respiratory effort for 20 seconds. But if the apnea alarm is set at 20 seconds, backup ventilation will not start until 20 seconds has passed. Some neonates become hemodynamically unstable if backup ventilation is delayed for that long. The patient may be more stable clinically if the alarm is set at 15 seconds.
6. We recommend observing the Edi signal of the infant for one to two hours before initiating NAVA to ensure the infant has a consistent respiratory drive. The most common patient failure is due to apnea. Excess sedation or analgesia can suppress the respiratory drive and contribute to patient failure on NAVA. Most premature infants need caffeine prior to the use of NAVA. Consider additional boluses and higher doses if apnea persists. Caffeine levels should be followed per your institution’s policy.
7. Weaning a patient from NAVA is different than weaning a patient from conventional ventilation. In the NAVA mode, it is not possible to wean the rate or pressure as these are determined by the patient. The only parameter that can be weaned is the NAVA level. As the NAVA level is lowered, work of breathing is shifted from the ventilator to the patient. It is recommended the NAVA level be lowered in increments of 0.5 while following the Edi peak. If the Edi peak increases significantly, then the patient may not be ready for weaning. It is also important to follow the peak inspiratory pressure trend. When this pressure has decreased to sufficiently low levels, it may be time to extubate.
NAVA challenges
Anea, which is a normal and frequent occurrence in the neonate, has been the biggest barrier to the use of NAVA in the NICU. When using the NAVA mode of ventilation, recurrent apnea results in frequent alarms and the ventilator switching to the backup mode of ventilation. In this mode, the rate is preset at 30 breaths per minute (bpm) with the pressure control above positive end-expiratory pressure set by the clinician.
The rate can be adjusted once the patient is in backup mode but defaults to 30 bpm each time the patient switches to backup mode. The clinician then needs to return the neonate to the NAVA mode of ventilation manually when the Edi signal returns.2 2his results in “alarm fatigue” and excess time at the bedside by the staff. It is essential the manufacturer upgrades the software to make the following modifications: alter the alarms when the neonate goes into backup ventilation, let the clinician preset the rate in backup ventilation, and allow the neonate to return to NAVA automatically when the Edi signal returns.
References
1. Sinderby C. NAVA – a new generation in respiratory therapy. Neonatal Intensive Care. 2006;19(4):32-4.
2. Maquet Critical Care AB. NAVA Pocket Guide. 2009.
Howard Stein, MD, FAAP, is a neonatologist at Toledo Children’s Hospital, in Toledo, Ohio. Contact him at howardstein@bex.net. Kimberly S. Firestone, BS, RRT, is neonatal outreach educator, Akron Children’s Hospital, Akron, Ohio. Diane Dunn, RRT, is education coordinator in the respiratory care department at Akron Children’s Hospital. Diane Howard, BEd, RRT, is respiratory education coordinator in the respiratory care department at Toledo Children’s Hospital.
What Is NAVA?
NAVA is a mode of ventilation which allows a patient to synchronize spontaneous respiratory effort with mechanical ventilation. Electrodes embedded within a nasogastric catheter detect the electrical activity of the diaphragm and transmit this information to the ventilator. The ventilator breath is triggered and terminated by changes in this electrical activity. The ventilator determines the inspiratory pressure in proportion to this electrical signal. Therefore, the patient determines respiratory rate, tidal volume, peak inspiratory pressure, mean airway pressure, and inspiratory and expiratory times.
