Rapid respiratory transition at birth as evaluated by electrical activity of the diaphragm in very preterm infants supported by nasal CPAP

NIV-NAVA versus NCPAP immediately after birth in premature infants: A randomized controlled trial

OBJECTIVE

To evaluate whether noninvasive-neurally adjusted ventilatory assist (NIV-NAVA) decrease respiratory efforts compared to nasal continuous positive airway pressure (NCPAP) during the first hours of life.

METHODS

Twenty infants born between 28⁺⁰ and 31⁺⁶ weeks were randomized to NIV-NAVA or NCPAP. Positive end-expiratory pressure was constantly kept at 6 cmH₂O for both groups and the NAVA level was 1.0 cmH₂O/µV for NIV-NAVA group. The electrical activity of diaphragm (Edi) were recorded for the first two hours.

RESULTS

Peak and minimum Edi decreased similarly in both groups (P = 0.98 and P = 0.59, respectively). Leakages were higher in the NIV-NAVA group than in the NCPAP group (P < 0.001). The neural apnea defined as a flat Edi for ≥ 5 s were less frequent in NIV-NAVA group than in NCPAP group (P = 0.046).

CONCLUSIONS

Immediately applied NIV-NAVA in premature infants did not reduce breathing effort, measured as peak Edi. However, NIV-NAVA decreased neural apneic episodes compared to NCPAP.

Respiratory muscle function in the newborn: a narrative review

Our aim was to summarise the current evidence and methods used to assess respiratory muscle function in the newborn, focusing on current and future potential clinical applications. The respiratory muscles undertake the work of breathing and consist mainly of the diaphragm, which in the newborn is prone to dysfunction due to lower muscle mass, flattened shape and decreased content of fatigue-resistant muscle fibres. Premature infants are prone to diaphragmatic dysfunction due to limited reserves and limited capacity to generate force and avoid fatigue. Methods to assess the respiratory muscles in the newborn include electromyography, maximal respiratory pressures, assessment for thoraco-abdominal asynchrony and composite indices, such as the pressure-time product and the tension time index. Recently, there has been significant interest and a growing body of research in assessing respiratory muscle function using bedside ultrasonography. Neurally adjusted ventilator assist is a novel ventilation mode, where the level of the respiratory support is determined by the diaphragmatic electrical activity. Prolonged mechanical ventilation, hypercapnia and hypoxia, congenital anomalies and systemic or respiratory infection can negatively impact respiratory muscle function in the newborn, while caffeine and synchronised or volume-targeted ventilation have a positive effect on respiratory muscle function compared to conventional, non-triggered or pressure-limited ventilation, respectively. IMPACT: Respiratory muscle function is impaired in prematurely born neonates and infants with congenital anomalies, such as congenital diaphragmatic hernia. Respiratory muscle function is negatively affected by prolonged ventilation and infection and positively affected by caffeine and synchronised compared to non-synchronised ventilation modes. Point-of-care diaphragmatic ultrasound and neurally adjusted ventilator assist are recent diagnostic and therapeutic technological developments with significant clinical applicability.

Neurally Adjusted Ventilatory Assist in Newborns

Patient-ventilator asynchrony is very common in newborns. Achieving synchrony is quite challenging because of small tidal volumes, high respiratory rates, and the presence of leaks. Leaks also cause unreliable monitoring of respiratory metrics. In addition, ventilator adjustment must take into account that infants have strong vagal reflexes and demonstrate central apnea and periodic breathing, with a high variability in breathing pattern. Neurally adjusted ventilatory assist (NAVA) is a mode of ventilation whereby the timing and amount of ventilatory assist is controlled by the patient's own neural respiratory drive. As NAVA uses the diaphragm electrical activity (Edi) as the controller signal, it is possible to deliver synchronized assist, both invasively and noninvasively (NIV-NAVA), to follow the variability in breathing pattern, and to monitor patient respiratory drive, independent of leaks. This article provides an updated review of the physiology and the scientific literature pertaining to the use of NAVA in children (neonatal and pediatric age groups). Both the invasive NAVA and NIV-NAVA publications since 2016 are summarized, as well as the use of Edi monitoring. Overall, the use of NAVA and Edi monitoring is feasible and safe. Compared with conventional ventilation, NAVA improves patient-ventilator interaction, provides lower peak inspiratory pressure, and lowers oxygen requirements. Evidence from several studies suggests improved comfort, less sedation requirements, less apnea, and some trends toward reduced length of stay and more successful extubation.

Cardiorespiratory monitoring in the delivery room using transcutaneous electromyography

OBJECTIVE

To assess feasibility of transcutaneous electromyography of the diaphragm (dEMG) as a monitoring tool for vital signs and diaphragm activity in the delivery room (DR).

DESIGN

Prospective observational study.

SETTING

Delivery room.

PATIENTS

Newborn infants requiring respiratory stabilisation after birth.

INTERVENTIONS

In addition to pulse oximetry (PO) and ECG, dEMG was measured with skin electrodes for 30 min after birth.

OUTCOME MEASURES

We assessed signal quality of dEMG and ECG recording, agreement between heart rate (HR) measured by dEMG and ECG or PO, time between sensor application and first HR read-out and agreement between respiratory rate (RR) measured with dEMG and ECG, compared with airway flow. Furthermore, we analysed peak, tonic and amplitude diaphragmatic activity from the dEMG-based respiratory waveform.

RESULTS

Thirty-three infants (gestational age: 31.7±2.8 weeks, birth weight: 1525±661 g) were included.18%±14% and 22%±21% of dEMG and ECG data showed poor quality, respectively. Monitoring HR with dEMG was fast (median 10 (IQR 10-11) s) and accurate (intraclass correlation coefficient (ICC) 0.92 and 0.82 compared with ECG and PO, respectively). RR monitoring with dEMG showed moderate (ICC 0.49) and ECG low (ICC 0.25) agreement with airway flow. Diaphragm activity started high with a decreasing trend in the first 15 min and subsequent stabilisation.

CONCLUSION

Monitoring vital signs with dEMG in the DR is feasible and fast. Diaphragm activity can be detected and described with dEMG, making dEMG promising for future DR studies.

Effects of skin-to-skin care on electrical activity of the diaphragm in preterm infants during neurally adjusted ventilatory assist

BACKGROUND

Skin-to-skin care (SSC) reduces neonatal mortality and morbidity and is widely implemented in the neonatal intensive care unit. However, changes in respiratory effort during SSC in ventilated preterm infants remain unclear.

AIMS

To evaluate the effect of SSC on electrical activity of the diaphragm (Edi) and vital signs in premature infants who are intubated and under neurally adjusted ventilatory assist ventilation.

STUDY DESIGN

We performed an observational cross-over study. Data were measured in three periods: before (pre-SSC period), during (SSC period), and after (post-SSC period) SSC. Stable 30-min data in each period were extracted.

SUBJECTS

Thirty-four SSC procedures were performed in 14 preterm infants with a median gestational age of 25.3 weeks (interquartile range, 24, 26.4) and a birth weight of 659 g (566, 694). The median postnatal age was 41 days (31, 53) at the study with a median postmenstrual age of 31.3 weeks (30.4, 32.5).

OUTCOME MEASURES

Median values of Edi peak, Edi minimum, respiratory rate, SpO₂, and heart rate were measured in each condition. The Kruskal-Wallis test with Bonferroni multiple comparisons was used to compare each parameter in each period.

RESULTS

Median Edi peak and Edi minimum values were significantly lower during SSC compared with pre- and post-SSC, without any change in respiratory rate, SpO₂, or heart rate.

CONCLUSIONS

Respiratory efforts as evaluated by Edi are significantly reduced during SSC in ventilated preterm infants.

How to improve CPAP failure prediction in preterm infants with RDS: a pilot study

We aimed to test the diagnostic accuracy in predicting continuous positive airway pressure (CPAP) failure in premature infants with respiratory distress syndrome (RDS) by integrating oxygen saturation (SpO₂)/fraction of inspired oxygen (FiO₂) (SF ratio) with the measurement of peak velocity of the right diaphragmatic excursions (RD-PV), during the inspiration (I-Peak) and expiratory (E-Peak) phases, performed by pulsed-wave Tissue Doppler imaging. This is a prospective, observational pilot study conducted over a 2-year period. Neonates at ≤ 32 weeks gestation supported by early CPAP were eligible. Natural surfactant was delivered via a minimally invasive technique. We performed serial measurements of SF ratio and RD-PV during the early post-natal hours to test the accuracy in predicting surfactant administration as well as invasive ventilation support within 72 h from birth because of the RDS worsening. Of 56 preterm infants enrolled, 34 (61%) failed CPAP support. SF ratio showed a significant inverse relationship with both Silverman-Andersen score at birth (rho = - 0.417; P = .001) and RD-PV [E-Peak] (rho = - 0.361; P = .007). We achieved a high accuracy in predicting CPAP failure (AUC = 95%; 95% CI, 89-100%) by integrating gender, SF ratio, and RD-PV [E-Peak] at the restricted, multivariate analysis.Conclusions: SF ratio and RD-PV, as measured by pulsed-wave Tissue Doppler, may help physicians to improve their confidence in optimizing therapeutic options in preterm infants with RDS. What is Known: • Continuous positive airway pressure is the recommended first-line treatment for respiratory distress syndrome in preterm infants, but failure rates remain unacceptably high. • Choosing the optimal treatment in terms of non-invasive ventilation effectiveness and timeliness of surfactant administration for these patients is often challenging, also due to our inability to identify a worsening respiratory failure. What is New: • The integration of oxygen saturation, as measured by SpO₂/FiO₂, with right diaphragm peak motion velocities, as measured by pulsed-wave tissue Doppler, allows for high prediction accuracy of non-invasive ventilation support failure in premature infants at risk of respiratory distress syndrome. • These measurements may help physicians in providing optimal supportive therapy for these patients.

The Effect of Initial Oxygen Exposure on Diaphragm Activity in Preterm Infants at Birth

Background: The initial FiO2 that should be used for the stabilization of preterm infants in the delivery room (DR) is still a matter of debate as both hypoxia and hyperoxia should be prevented. A recent randomized controlled trial showed that preterm infants [gestational age (GA) < 30 weeks] stabilized with an initial high FiO2 (1.0) had a significantly higher breathing effort than infants stabilized with a low FiO2 (0.3). As the diaphragm is the main respiratory muscle in these infants, we aimed to describe the effects of the initial FiO2 on diaphragm activity. Methods: In a subgroup of infants from the original bi-center randomized controlled trial diaphragm activity was measured with transcutaneous electromyography of the diaphragm (dEMG), using three skin electrodes that were placed directly after birth. Diaphragm activity was compared in the first 5 min after birth. From the dEMG respiratory waveform several outcome measures were determined for comparison of the groups: average peak- and tonic inspiratory activity (dEMGpeak and dEMGton, respectively), inspiratory amplitude (dEMGamp), area under the curve (dEMGAUC) and the respiratory rate (RR). Results: Thirty-one infants were included in this subgroup, of which 29 could be analyzed [n = 15 (median GA 28.4 weeks) and n = 14 (median GA 27.9 weeks) for the 100 and 30% oxygen group, respectively]. Tonic diaphragm activity was significantly higher in the high FiO2-group (4.3 ± 2.1 μV vs. 2.9 ± 1.1 μV; p = 0.047). The other dEMG-parameters (dEMGpeak, dEMGamp, dEMGAUC) showed consistently higher values in the high FiO2 group, but did not reach statistical significance. Average RR showed similar values in both groups (34 ± 9 vs. 32 ± 10 breaths/min for the high and low oxygen group, respectively). Conclusion: Preterm infants stabilized with an initial high FiO2 showed significantly more tonic diaphragm activity and an overall trend toward a higher level of diaphragm activity than those stabilized with an initial low FiO2. These results confirm that a high initial FiO2 after birth stimulates breathing effort, which can be objectified with dEMG.