Application of neurally adjusted ventilatory assist in ventilator weaning of infants ventilator weaning

Abstract Background To analyze the application of neurally adjusted ventilatory assist in ventilator weaning of infants. Methods A total of 25 infants (15 boys and 10 girls) who were mechanically ventilated by PICU in Hubei Maternal and Child Health Hospital were selected as the study subjects. After the improvement of the basic disease, regular spontaneous breathing, and the withdrawal of the ventilator, all the children obtained the electrical activity of the diaphragm (EAdi) signal. Then, each child was given CPAP and NAVA mode mechanical ventilation 1 h before the withdrawal of the ventilator. Each detection index was recorded 30 min after each mode of ventilation. Results Two of the 25 children were tracheotomized because of respiratory muscle weakness and could not be converted to NAVA mode without the EAdi signal. Hemodynamic indexes were not statistically different between the two groups of CPAP and NAVA. PaCO2 is not significantly different in the two modes, and both were at normal levels. The PIP in NAVA mode is lower than that in CPAP mode (p < .05), and its EAdi signal was correspondingly low. There were significant differences in the peak pressure (Ppeak), mean pressure (Pmean), and compliance and mean arterial pressure (p < .01) between the CPAP and NAVA model ventilation in 23 patients. Conclusion NAVA can significantly improve the coordination of patients. The therapeutic effect of NAVA was better, which was beneficial to the prognosis of patients and had positive application value in the withdrawal of ventilators in patients.


BACKGROUND
Mechanical ventilation can improve patient oxygenation, correct carbon dioxide storage, and provide time guarantee for the treatment of primary disease. However, when the underlying disease is controlled, how to assess whether patients have ventilator weaning conditions has become a difficult problem for clinicians. Available data indicate that about 60%-65% of patients admitted to intensive care unit (ICU) for mechanical ventilation survive, about 85% of mechanically ventilated patients are successfully extubated. In comparison 15% or more patients require re-intubation within approximately 48 h (Mac-Intyr, 2012). Due to the prolonged duration of mechanical ventilation, it can increase complications such as ventilator-related lung injury (VILI), ventilator atrophy, ventilator-mediated diaphragmatic dysfunction (VIDD) (Laghi & Shaikh, 2014), and reduce the quality of life of patients and prolong hospital stay. At present, many parameters and tests are used to determine preparation for offline and extubation, including breathing rate, minute ventilation (MV), shallow fast breathing index, primary breathing test(SBT), T-tube test, and balloon leak test. A series of retrospective studies have shown that these indicators cannot alone predict successful withdrawal. However, there are certain limitations and re-intubation rates, and the above methods are challenging to apply in infants. At the same time, most traditional ventilation modes are triggered by pressure or flow. However, these triggering methods will be caused by air leakage (Moerer et al., 2008), improper trigger sensitivity setting (Sinderby et al., 1999), the need to overcome endogenous positive end-expiratory pressure (PEEP) (Esquinas, 2013), and other problems, leading to delayed triggering and/or false triggering, increasing the work of the respiratory muscles of the patient, causing fatigue of the respiratory muscles, and adversely affecting the patient's prognosis (Purro et al., 2000).
Therefore, it is critical to assess whether children with ICU mechanical ventilation have ventilator weaning conditions. We urgently need a new ventilation mode to change this situation. Studies found that (Beck et al., 2000(Beck et al., , 2006Finucane et al., 2005)  that changes according to the respiratory frequency and intensity sig-nals emitted by the patient's central nervous system and keeps synchronization in real time (Ouattara, 2012).
Previous studies have shown that the NAVA model can be used in neonates and premature infants, and it is safe, effective and well tolerated (Stein & Firestone, 2014). However, compared with the current traditional mechanical ventilation model (CPAP), its safety, effectiveness, and prognosis of patients are low. At present, there are only small sample surveys at home and abroad. We need further research to provide a theoretical basis for later clinical treatment. In this experiment, we will compare the differences between Nava mode mechanical ventilation and traditional ventilation mode (CPAP) after regular spontaneous breathing in 25 children with PICU mechanical ventilation and explore the application of neurally adjusted ventilatory assist in infant ventilator weaning.

Patients
This study included 25 infants with mechanical ventilation in PICU.

Statistics analysis
The data were analyzed with SPSS ll.5 (Chicago, IL, USA) for medical statistics. Count data were expressed as mean ±SD. Parameter statistics used paired t test and independent t test. Statistical significance was set at p < .05 level.

RESULT
Two of the 25 children were unable to switch to NAVA mode due to weakness in the respiratory muscles and no EAdi signal. There was one child with glycogenosis type II, one child with myasthenia gravis that caused weaning failure, and tracheotomy was performed.
Re-tracheal intubation after ventilator withdrawal and re-weaning after mechanical ventilation were successful in five children, including Guillain-Barre syndrome, purulent meningitis, ICU-acquired myasthenia, acute respiratory distress syndrome (ARDS), and myasthenia gravis. Analysis of the peak EAdi signal before NAVA ventilation and the peak EAdi signal after the second intubation in five children with failed intubation and secondary intubation were 11.14-3.

Comparison of indicators of CPAP and NAVA models
The comparison of various indicators of CPAP and NAVA modes in 23 patients is shown in Table 3. Hemodynamic indexes, including CVP, were not statistically different between the two groups of CPAP and NAVA. PCO 2 is not significantly different in the two modes, both were at normal levels, the peak inspiratory pressure (PIP) in NAVA mode is lower than that in CPAP mode (p < .05), and its EAdi signal was correspondingly low, which were (8.24-2.6) 1.1 V and (7.04-1.6) 1.1 V (p < .05). In addition, as far as the asynchronous index (AI) is concerned, the NAVA mode is also significantly lower than the CPAP mode (p < .01). There were statistically significant differences in ventilator peak inspiratory pressure (Ppeak), mean inspiratory pressure (Pmean), and compliance and mean arterial pressure (p < .01). The application time of NAVA mode is 24-240 h, with an average of 43.84-28.7 h.

DISCUSSION
For patients with a critical illness, successful ventilator weaning may be a stressful process experienced by the body. Its success depends on the relationship between multiple organ function stability and dysfunction. It appears that ventilator weaning failures are often the result of the multi-layered dysfunction of lung, muscle, nerve, heart, and brain.
Other factors such as metabolic disorders, malnutrition, and uncontrolled infections are equally important (Tang et al., 2013).
Mechanical ventilation is a supportive method for children with PICU respiratory failure. Basic lung injury and man-machine counteraction, improper use of ventilator, and ventilator-related lung injury further aggravate respiratory failure, prolong hospital stay, and increase mortality. It is extremely important to synchrony of patientventilator, reduce ventilator-related lung injury, and select ventilator mode when working with patients. Premature or delayed weaning, mechanical ventilation-induced lung injury will seriously affect patients' prognosis (Chen et al., 2016). Patients with CPAP ventilation would significantly increase their breathing frequency and the work of respiratory muscles when their thoracic compliance changed (Bersten et al., 1989;Branson et al., 1994). Moreover, it was found that the incidence rate of the asynchronous index (AI) in the PSV mode was 36%, which was significantly higher than that in the NAVA mode. These problems will reduce the comfort of mechanical ventilation and increase dependence on sedatives (Bonacina et al., 2019). The results showed that the asynchronous index of Nava model was significantly lower than that of CPAP mode. Abbreviations: CI, cardiac index; HR, heart rate; CVP, central venous pressure; MAP, mean arterial pressure. *Indicates a significant correlation between before and after treatment (CPAP vs. NAVA). Our results also show that patients with NAVA require significantly lower PIP than CPAP, indicating that NAVA has a greater potential to reduce lung injury than CPAP. Twenty-three children with successful weaning used CPAP and NAVA modes. There were statistically significant differences in ventilator peak pressure (Ppeak), mean pressure (Pmean), and compliance, suggesting that NAVA ventilation mode is more suitable for patients' physiology and lower airway pressure. It can reduce ventilator-related barotrauma, and there is a statistical difference in the mean arterial pressure, which corresponds to the mean pressure lower than the NAVA ventilation phase, which indicates that the NAVA ventilation chest pressure is lower and the hemodynamic effect is smaller. NAVA is Conducive to the recovery of heart and lung function in children (Sinderby et al., 2007). Beck et al. (2009) sequentially applied conventional mechanical ventilation and NAVA to seven low birth weight infants before and after extubation and compared the coordination between EAdi and pressure support level in these two ventilation modes. The results showed that NAVA relied on EAdi signal to perceive the drive of respiratory center of infants, which improved the synchrony of human and machine more than traditional ventilation mode, and was consistent with the results of this study. Breatnach et al. (2010) reported that in 16 children aged between two days and four years who needed mechanical ventilation, the peak airway pressure decreased by 28% after 30 min of NAVA ventilation and 32% after 3 h.

TA B L E 3 Comparison of Edi peak value and Edi low value
In patients with acute respiratory failure, there was a significant negative correlation between EAdi and stress support which means as pressure support increases, EAdi decreases proportionally. It is indicated that the strength of EAdi is an indicator of the respiratory load.
Since the acquisition of EAdi signals plays a crucial role in NAVA, it can be used for neuromuscular diseases to evaluate whether the muscle function is restored and choose a more appropriate offline time.
In this trial, the peak Edi of children who failed to withdraw was sig-

CONFLICT OF INTEREST
The authors declare no conflict of interest.

DATA AVAILABILITY STATEMENT
The datasets generated and analyzed during the current study are available from the corresponding author on reasonable request.