Feasibility and physiological effects of noninvasive neurally adjusted ventilatory assist in preterm infants

Abstract

BackgroundNoninvasive neurally adjusted ventilator assist (NIV-NAVA) was introduced to our clinical practice via a pilot and a randomized observational study to assess its safety, feasibility, and short-term physiological effects.MethodsThe pilot protocol applied NIV-NAVA to 11 infants on nasal CPAP, high-flow nasal cannula, or nasal intermittent mandatory ventilation (NIMV), in multiple 2- to 4-h periods of NIV-NAVA for comparison. This provided the necessary data to design a randomized, controlled observational crossover study in eight additional infants to compare the physiological effects of NIV-NAVA with NIMV during 2-h steady-state conditions. We recorded the peak inspiratory pressure (PIP), FiO₂, Edi, oxygen saturations (histogram analysis), transcutaneous PCO₂, and movement with an Acoustic Respiratory Movement Sensor.ResultsThe NAVA catheter was used for 81 patient days without complications. NIV-NAVA produced significant reductions (as a percentage of measurements on NIMV) in the following: PIP, 13%; FiO₂, 13%; frequency of desaturations, 42%; length of desaturations, 32%; and phasic Edi, 19%. Infant movement and caretaker movement were reduced by 42% and 27%, respectively. Neural inspiratory time was increased by 39 ms on NIV-NAVA, possibly due to Head's paradoxical reflex.ConclusionNIV-NAVA was a safe, alternative mode of noninvasive support that produced beneficial short-term physiological effects, especially compared with NIMV.

Figure 1

The randomized crossover design of the observational study. All infants were on NIMV at the start and finish of the protocol. After set up, NIV-NAVA was applied for up to 30 min to determine optimum parameters, followed by at least 30 min of NIMV. Infants were then randomized to either continue NIMV or NIV-NAVA for 3 h after nursing care and then crossed over to the alternate mode until after the next nursing care. A 2-h recording period was performed after a 1-h washout period following the nursing care. Infants were not handled during the recording unless care was necessary.

Figure 2

Timing relationships between the Edi, airway flow, and airway pressure (Paw) are shown during NIV-NAVA (a) and the Edi and Paw during NIMV (b). Shown are time points at the start of neural inspiration (A), the start of the ventilator breath (B), the end of neural inspiration (C), the start of pneumatic expiration (D), and the end of neural expiration (E). An unassisted breath is indicated by a star that was chosen for possible comparison, which was not affected by the random NIMV breaths. Time points A, C, and E were defined similarly for the unassisted breaths in b.

Figure 3

Differences for each measurement while on NIV-NAVA expressed as a percentage of those while on NIMV. There were significant reductions in the peak inspiratory pressure and FiO₂ with no difference in the distribution of saturations or the PtcCO₂. There were significant reductions in the frequency and depth of desaturations, the phasic Edi, and in the amount of infant and caretaker movement. There were no differences in the mean airway pressures between modes of support. Significance, starred bars = P<0.01.