Randomized Crossover Study of Neurally Adjusted Ventilatory Assist (NAVA) in Preterm Infants

Application of Neurally Adjusted Ventilatory Assist (NAVA) in Preterm Infants and Assessment of Its Benefits Compared to Synchronized Intermittent Mandatory Ventilation (SIMV) With Pressure Support (PS)

The purpose of this study is to test the hypothesis that neurally adjusted ventilatory assist (NAVA) will allow to lower the ventilator pressure at equivalent fractions of inspiratory oxygen (FiO2) and partial pressure of CO2 of capillary blood in preterm infants in comparison with currently used standard ventilation (synchronized intermittent mandatory ventilation with pressure-support ventilation, SIMV+PSV).

The investigators will apply crossover comparison in preterm infants who received a ventilatory support. In patient whose frequency of mandatory support is under 25, the two ventilatory modes (SIMV+PSV and NAVA) are delivered by the same ventilator (Servo-I; Maquet Critical Care AB, Solna, Sweden) and will set to maintain similar blood gas analysis results. Determination of the type of ventilatory mode used is performed using a cluster randomization. The randomized order of ventilatory mode will be used during total 9 hours; one mode for 4 hours and another mode for 5 hours. To rule out carry-over effects, a 1-hour interval for washout was guaranteed between modes. Recordings will be obtained over a total 8 hours.

Neurally adjusted ventilatory assist (NAVA) utilizes the electrical activity of the diaphragm (EAdi) to trigger and cycle-off breaths, and therefore presents a means of bypassing the ventilator circuit, and the inherent delays with pneumatic triggering. This is a processed signal, which is not artificially influenced by changes in muscle length, chest wall configuration, and/or lung volume. It represents the summation of muscle motor unit recruitment and/or firing rate, and correlates with phrenic nerve activity. In this mode, the amount of support pressure is coupled with the magnitude of the EAdi. The proportion of support pressure to EAdi (NAVA level) is adjustable.

Capillary blood pH checked immediately after the 4-hour respiratory support with each ventilator mode

Capillary blood pCO2 checked immediately after the 4-hour respiratory support with each ventilator mode

Capillary blood pO2 checked immediately after the 4-hour respiratory support with each ventilator mode

Capillary blood HCO3 checked immediately after the 4-hour respiratory support with each ventilator mode

Inclusion Criteria: preterm infants mechanically ventilated ventilatory set frequency is under 25 with informed consent of their parents Exclusion Criteria: major congenital anomalies patients without self respiratory effort use of sedative or anesthetic drugs grade III or IV intraventricular hemorrhage phrenic nerve palsy or insufficiency