Abstract
Background:
Neurally-adjusted ventilatory assist (NAVA) provides proportional ventilatory support based on the patient's respiratory drive using a specialized catheter to measure the electrical activity of the diaphragm (EAdi). Respiratory variability and apnea are challenges when treating the premature infant. With NAVA, if the neonate has a respiratory pause lasting more than a predetermined time (apnea time), back up pressure control ventilation is provided until an EAdi is detected and NAVA ventilation resumes. In theory, this allows the clinician to set a minimum spontaneous respiratory rate. Short apnea times provide backup ventilation during periods of normal physiologic respiratory variability potentially resulting in over ventilation and suppression of spontaneous respiratory drive. Longer apnea times may allow more spontaneous ventilation but potentially result in clinical deterioration from insufficient respiratory support because of longer periods without ventilation. The objective of this study is to determine the effect of changing the apnea time in neonates on noninvasive NAVA (NIV-NAVA).
Methods:
Two center, prospective, one-factorial, interventional study of neonates on NIV-NAVA. Apnea time was randomly set at either 2 or 5 s for 2 hours and then interchanged. Clinically significant events (CSE), EAdi peak/min, and switches/min to backup (switches/min) and %/minute in backup (%/min) were collected. Statistics were paired t-tests. IRB approval obtained.
Results:
Fifteen neonates 26+1.6 weeks gestational age weighing 893+202 grams at birth were studied at 15+16 days. Diagnoses included respiratory distress syndrome, apnea of prematurity. All neonates received caffeine. At 2-s versus 5-s apnea time, switches into backup decreased from 2.5 to 0.5 switches/min (p < 0.000003) and time spent in back up decreased from 9 to 2%/min (p < 0.00002). There was an increase from 2 to 7 CSE/hour (p < 0.0003). EAdi peak and min were unchanged.
Conclusions:
Neonates on NIV NAVA have fewer CSE while on a shorter apnea time, although they spend slightly more time in back up ventilation. Over 90% of ventilation was spontaneous in NAVA for both groups. EAdi peak and min remained similar despite changes in apnea time; therefore, neonates were not over supported during periods of normal respiratory variability. This suggests short apnea times should be utilized for patients ventilated with NIV NAVA to promote clinical stability and decrease CSE.
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