Nasal high-flow therapy decreased electrical activity of the diaphragm in preterm infants during the weaning phase

Diaphragmatic electromyography in infants: an overview of possible clinical applications

Preterm infants often experience breathing instability and a hampered lung function. Therefore, these infants receive cardiorespiratory monitoring and respiratory support. However, the current respiratory monitoring technique may be unreliable for especially obstructive apnea detection and classification and it does not provide insight in breathing effort. The latter makes the selection of the adequate mode and level of respiratory support difficult. Electromyography of the diaphragm (dEMG) has the potential of monitoring heart rate (HR) and respiratory rate (RR), and it provides additional information on breathing effort. This review summarizes the available evidence on the clinical potential of dEMG to provide cardiorespiratory monitoring, to synchronize patient-ventilator interaction, and to optimize the mode and level of respiratory support in the individual newborn infant. We also try to identify gaps in knowledge and future developments needed to ensure widespread implementation in clinical practice. IMPACT: Preterm infants require cardiorespiratory monitoring and respiratory support due to breathing instability and a hampered lung function. The current respiratory monitoring technique may provide unreliable measurements and does not provide insight in breathing effort, which makes the selection of the optimal respiratory support settings difficult. Measuring diaphragm activity could improve cardiorespiratory monitoring by providing insight in breathing effort and could potentially have an important role in individualizing respiratory support in newborn infants.

Positive pressure ventilation in the weaning of preterm newborns

BACKGROUND

Weaning from invasive mechanical ventilation (IMV) of preterm newborns (PTNB) is one of the critical stages of life support in the Neonatal Intensive Care Unit (NICU). Noninvasive positive pressure ventilation (NPPV) has been used to facilitate weaning from IMV and includes continuous positive airway pressure (CPAP) without or with inspiratory pressure support (bilevel NPPV). Nevertheless, there is little information about their adherence and success rate during weaning process.

METHODS

In this retrospective cohort study, weaning data from patients admitted to a NICU from the northeast region of Brazil were analyzed. Sample was composed of PTNB submitted to IMV and divided in two groups according to the weaning strategy adopted: bilevel NPPV or NCPAP. Weaning failure was defined as returning to IMV within less than 48 h after extubation.

RESULTS

Fifty-seven PTNB were included. Majority were females, had caesarean delivery, very low weight upon birth (760-1480 g) and neonatal hypoxemia scores (Apgar) <7 in the first minute. Respiratory distress syndrome occurred in 56.7% of PTNB whilst respiratory infections occurred in 35.1% of patients. Bilevel NPPV was the most chosen modality of weaning. No difference in success rate was found between bilevel NPPV and NCPAP (P=0.17).

CONCLUSIONS

In this study, the application of noninvasive ventilation in preterm newborns for weaning from IMV was similar success rate between bilevel NPPV and NCPAP.

Diaphragm electrical activity during weaning of nasal high-flow therapy in preterm infants

OBJECTIVE

To determine whether electrical activity of the diaphragm (Edi) changes with weaning nasal high-flow (HF) therapy in preterm infants according to a standardised protocol.

DESIGN

Prospective observational cohort study.

SETTING

Neonatal intensive care unit.

PATIENTS

Preterm infants born at <32 weeks gestation, receiving nasal HF as part of routine clinical care.

INTERVENTIONS

Infants recruited to the study had their HF weaned according to set clinical criteria. Edi was measured using a modified gastric feeding tube serially from baseline (pre-wean) to 24-hours post-wean.

MAIN OUTCOME MEASURES

Change in Edi from baseline was measured at four time points up to 24 hours after weaning. Minimum Edi during expiration, maximum Edi during inspiration and amplitude of the Edi signal (Edi_delta) were measured. Clinical parameters (heart rate, respiratory rate and fraction of inspired oxygen) were also recorded.

RESULTS

Forty preterm infants were recruited at a mean corrected gestational age of 31.6 (±2.7) weeks. Data from 156 weaning steps were analysed, 91% of which were successful. Edi did not change significantly from baseline during flow reduction steps, but a significant increase in diaphragm activity was observed when discontinuing HF (median increase in Edi_delta immediately post-discontinuation 1.7 µV (95% CI: 0.6 to 3.0)) and at 24 hours 1.9 µV (95% CI: 0.7 to 3.8)). No significant difference in diaphragm activity was observed between successful and unsuccessful weaning steps.

CONCLUSIONS

A protocolised approach to weaning has a high probability of success. Edi does not change with reducing HF rate, but significantly increases with discontinuation of HF from 2 L/min.

Diaphragmatic electromyography during a spontaneous breathing trial to predict extubation failure in preterm infants

BACKGROUND

Premature attempts at extubation and prolonged episodes of ventilatory support in preterm infants have adverse outcomes. The aim of this study was to determine whether measuring the electrical activity of the diaphragm during a spontaneous breathing trial (SBT) could predict extubation failure in preterm infants.

METHODS

When infants were ready for extubation, the electrical activity of the diaphragm was measured by transcutaneous electromyography (EMG) before and during a SBT when the infants were on endotracheal continuous positive airway pressure.

RESULTS

Forty-eight infants were recruited (median (IQR) gestational age of 27.2 (25.6-30.4) weeks). Three infants did not pass the SBT and 13 failed extubation. The amplitude of the EMG increased during the SBT [2.3 (1.5-4.2) versus 3.5 (2.1-5.3) µV; p < 0.001]. In the whole cohort, postmenstrual age (PMA) was the strongest predictor for extubation failure (area under the curve (AUC) 0.77). In infants of gestational age <29 weeks, the percentage change of the EMG predicted extubation failure with an AUC of 0.74 while PMA was not associated with the outcome of extubation.

CONCLUSIONS

In all preterm infants, PMA was the strongest predictor of extubation failure; in those born <29 weeks of gestation, diaphragmatic electromyography during an SBT was the best predictor of extubation failure.

IMPACT

Composite assessments of readiness for extubation may be beneficial in the preterm population. Diaphragmatic electromyography measured by surface electrodes is a non-invasive technique to assess the electrical activity of the diaphragm. Postmenstrual age was the strongest predictor of extubation outcome in preterm infants. The change in diaphragmatic activity during a spontaneous breathing trial in extremely prematurely born infants can predict subsequent extubation failure with moderate sensitivity and specificity.

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.

Electrical activity of the diaphragm following a loading dose of caffeine citrate in ventilated preterm infants

BACKGROUND

Administration of caffeine citrate can facilitate extubation. Our aim was to determine whether a loading dose of caffeine citrate given to ventilated, preterm infants affected the diaphragm electrical activity.

METHODS

Infants <34 weeks of gestational age were recruited if requiring mechanical ventilation and prescribed a loading dose of caffeine citrate. Surface electrodes recorded the electrical activity of the diaphragm (dEMG) before and after administration of intravenous caffeine citrate. The mean amplitude of the EMG (dEMG) trace and the mean area under the EMG curve (aEMGc) were calculated.

RESULTS

Thirty-two infants were assessed with a median gestational age of 29 (27-31) weeks. The dEMG amplitude increased, peaking at 25 min post administration (p = 0.006), and the increase in aEMGc (p = 0.004) peaked at 30 min; the differences were not significant after 60 min. At 20 min, there was an increase in minute volume (p = 0.034) and a reduction in the peak inspiratory pressure (p = 0.049).

CONCLUSIONS

We have demonstrated a transient increase in both electrical activity of the diaphragm and respiratory function following an intravenous loading dose of caffeine citrate.

Diaphragm electromyography results at different high flow nasal cannula flow rates

Heated, humidified, high-flow nasal cannula (HHHFNC) is increasingly being used, but there is a paucity of evidence as to the optimum flow rates in prematurely born infants. We have determined the impact of three flow rates on the work of breathing (WOB) assessed by transcutaneous diaphragm electromyography (EMG) amplitude in infants with respiratory distress or bronchopulmonary dysplasia (BPD). Flow rates of 4, 6 and 8 L/min were delivered in random order. The mean amplitude of the EMG trace and mean area under the EMG curve (AEMGC) were calculated and the occurrence of bradycardias and desaturations recorded. Eighteen infants were studied with a median gestational age of 27.8 (range 23.9-33.5) weeks and postnatal age of 54 (range 3-122) days. The median flow rate prior to the study was 5 (range 3-8) L/min and the fraction of inspired oxygen (FiO₂) was 0.29 (range 0.21-0.50). There were no significant differences between the mean amplitude of the diaphragm EMG and the AEGMC and the number of bradycardias or desaturations between the three flow rates.Conclusions: In infants with respiratory distress or BPD, there was no advantage of using high (8 L/min) compared with lower flow rates (4 or 6 L/min) during support by HHHFNC. What is known: • Humidified high flow nasal cannulae (HHHFNC) is increasingly being used as a non-invasive form of respiratory support for prematurely born infants. • There is a paucity of evidence regarding the optimum flow rate with 1 to 8 L/min being used. What is new: • We have assessed the work of breathing using the amplitude of the electromyogram of the diaphragm at three HHHFNC flow rates in infants with respiratory distress or BPD. • No significant differences were found in the EMG amplitude results or the numbers of bradycardias or desaturations at 4, 6 and 8 L/min.