Feasibility Study Over the NAVA Mode in Noninvasive Ventilation After Cardiac Surgery in Infants.

Feasibility Study Over the Neurally Adjusted Ventilatory Assist (NAVA) Mode in Noninvasive Ventilation After Cardiac Surgery in Infants.

Neonates who underwent cardiac surgery with cardiopulmonary bypass almost always require non-invasive respiratory support (NIV) in relay to conventional ventilation. Current nasal interfaces do not generally allow synchronised bilevel ventilation. NIV-NAVA mode allows, through an oesophageal catheter, to record the electrical activity of the diaphragm and thereby synchronize breaths from the ventilator on the inspiratory efforts of the child. Moreover, the pressure support delivered by the ventilator may be proportional to the diaphragmatic effort developed by the child. This mode, associated with the interface Miniflow®, could increase the comfort of the child by allowing a more efficient synchronization and reducing its respiratory work. To our knowledge, this ventilation mode with this interface has not been evaluated in the postoperative period of cardiac surgery in the newborns. The purpose of this study is to evaluate the feasibility of this ventilatory mode and evaluate its influence on ventilatory parameters of this category of infants.

Study Design:

Single centre prospective crossover study

Study Objectives:

Main objectives:

• Assessment of the feasibility of non invasive ventilation in NIV-NAVA mode via Miniflow® interface in infants of less than 3.5 kg after cardiac surgery with cardiopulmonary bypass.

• Evaluation of the following parameters:

  • Implementation of the interface
  • Air leaks
  • Placement and contention of oesophageal probe
  • Quality of synchronization
  • Obstruction of the probe
  • Risk of nasal wounds

Secondary objectives:

• Comparison of ventilation parameters between nasal Continuous Positive Airway Pressure (nCPAP) mode and NIV-NAVA mode

• Evaluation of the following parameters:

  • Breathing rhythm
  • Tidal volume
  • PEEP
  • Inspiratory pressure
  • FiO2
  • PaO2
  • PaCO2
  • pH

• Evolution of EAdi min and EAdi max parameters in NIV-NAVA mode (EAdi : diaphragmatic electric activity)

Conduct of the study:

First phase: placement of EADI catheter and extubation

When extubation criteria are met, the oesophageal EADI catheter is placed according to the manufacturer's instructions. The ventilation mode is then switched to Pressure Support Mode with the same Peep as in the previous mode and a pressure support of 10 cmH2O.

During 30 minutes, trends in respiratory rate, tidal volume, PEEP, inspiratory pressure, FiO2, EADI min, EADi max are recorded.

After 30 minutes, an arterial blood gas analysis is performed to determine the values of PaCO2, PaO2 and pH before randomization.

The child is extubated according to the procedures of the service and the non-invasive ventilation relay is introduced through the Miniflow® interface with nasal prongs adapted to the morphology of the child. An adrenaline nebulisation can be given before starting NIV in case of respiratory distress due to laryngeal oedema.

Second phase: nCPAP or NIV-NAVA

Following randomisation, the child is included in the "nCPAP first" arm or "NIV-NAVA first" arm and is ventilated in the designated mode for 30 minutes. During the first 15 minutes, the ventilation parameters are adapted according to the procedures below:

nCPAP parameters adaptation:

• PEEP and FiO2 as previously set in invasive ventilation;
• FiO2 according to target SpO2 values of the child and/or 10% higher than FiO2 in invasive ventilation mode;
• PEEP between 4-6 cmH2O in order to minimize respiratory efforts.

NIV-NAVA parameters adaptation:

• PEEP and FiO2 as previously set in invasive ventilation;
• Adaptation of the NIV-NAVA level to reach a EADi level equal to the mean EADi level over the last 5 minutes of the invasive mode. Inspiratory pressure and tidal volume are limited respectively to 30 cmH2O and 8 ml/kg.
• FiO2 according to target SpO2 values of the child and/or 10% higher than FiO2 in invasive ventilation mode ;
• PEEP between 4-6 cmH2O in order to minimize respiratory efforts.

Over the last 15 minutes of this ventilation mode, trends in respiratory rate, tidal volume, PEEP, inspiratory pressure, FiO2, EADI min, EADi max are recorded.

On Minutes M16, M21 and M29 in NIV-NAVA mode, synchronisation data are recorded : auto-triggering, double triggering, inspiration beginning and ending.

After 30 minutes, an arterial blood gas analysis is performed to determine the evolution of the values of PaCO2, PaO2 and pH.

At any time, if the re-intubation criteria are met, the child is re-intubated and returned to conventional ventilation. He is then excluded of the study.

Third phase: nCPAP or NIV-NAVA

The ventilation mode is changed from nCPAP to NIV-NAVA or from NIV-NAVA to nCPAP. The adaptation protocol and the recorded parameters are the same as in the second phase.

After 30 minutes, an arterial blood gas analysis is performed to determine the evolution of the values of PaCO2, PaO2 and pH.

At any time, if the re-intubation criteria are met, the child is re-intubated and returned to conventional ventilation. He is then excluded of the study.

Fourth phase: end of the study

The study concludes at the end of the third phase. The child is left in the better tolerated ventilation mode, as judged by the clinician.

Inclusion Criteria:

• Weight ≤ 5 kg
• Postoperative period of cardiac surgery with cardiopulmonary bypass (max 10 days after surgery)
• Conventional ventilation
• Agreement with the extubation criteria
• Arterial line

Exclusion Criteria:

• High frequency oscillation ventilation
• Extubation criteria not fulfilled
• Proven or suspected sepsis
• Absence of arterial line
• Oesophageal pathology (Excepted gastro-oesophageal reflux)