Electrical activity of the diaphragm (Edi) values and Edi catheter placement in non-ventilated preterm neonates

Novel forms of ventilation in neonates: Neurally adjusted ventilatory assist and proportional assist ventilation

Patient-triggered modes of ventilation are currently the standard of practice in the care of term and preterm infants. Maintaining spontaneous breathing during mechanical ventilation promotes earlier weaning and possibly reduces ventilator-induced diaphragmatic dysfunction. A further development of assisted ventilation provides support in proportion to the respiratory effort and enables the patient to have full control of their ventilatory cycle. In this paper we will review the literature on two of these modes of ventilation: neurally adjusted ventilatory assist (NAVA) and proportional assist ventilation (PAV), propose future studies and suggest clinical applications of these modes.

Case Report: Neurally adjusted ventilatory assist as an effective rescue treatment for pulmonary interstitial emphysema in extremely low birth weight infants

Pulmonary interstitial emphysema (PIE) is a complication observed in extremely low birth weight (ELBW) infants on mechanical ventilation. Despite various proposed therapeutic interventions, the success rates have shown inconsistency. Neurally adjusted ventilatory assist (NAVA) stands out as a novel respiratory support mode, offering lower pressure and tidal volume in comparison to conventional ventilation methods. In this case report, we present five ELBW infants with refractory PIE who were transitioned to NAVA ventilation. Following the switch to NAVA, all cases of PIE gradually resolved. In contrast to traditional modes, NAVA provided respiratory support with significantly lower fraction of inspired oxygen, reduced peak inspiratory pressure, diminished mean airway pressure, and decreased tidal volume within 7 days of NAVA utilization (p = 0.042, 0.043, 0.043, and 0.042, respectively). Consequently, we propose that NAVA could serve as a valuable rescue treatment for ELBW infants with PIE.

Evaluation of NAVA-PAP in premature neonates with apnea of prematurity: minimal backup ventilation and clinically significant events

Background

Neonates with apnea of prematurity (AOP) clinically deteriorate because continuous positive airway pressure (CPAP) provides inadequate support during apnea. Neurally adjusted ventilatory assist (NAVA) provides proportional ventilator support from the electrical activity of the diaphragm. When the NAVA level is 0 cmH2O/mcV (NAVA-PAP), patients receive CPAP when breathing and backup ventilation when apneic. This study evaluates NAVA-PAP and time spent in backup ventilation.

Methods

This was a prospective, two-center, observational study of preterm neonates on NAVA-PAP for AOP. Ventilator data were downloaded after 24 h. The number of clinically significant events (CSEs) was collected. A paired t-test was used to perform statistical analysis.

Results

The study was conducted on 28 patients with a gestational age of 25 ± 1.8 weeks and a study age of 28 ± 23 days. The number of CSEs was 4 ± 4.39/24 h. The patients were on NAVA-PAP for approximately 90%/min, switched to backup mode 2.5 ± 1.1 times/min, and spent 10.6 ± 7.2% in backup.

Conclusion

Preterm neonates on NAVA-PAP had few CSEs with minimal time in backup ventilation.

Inter-rater reliability of the Silverman and Andersen index-a measure of respiratory distress in preterm infants

BACKGROUND

There are various methods of respiratory support available to optimize respiratory function in preterm infants. Respiratory scoring tools might provide information on which method to choose and the level and duration of support needed. Before implementing a respiratory scoring tool in our clinical practice, we aimed to test the inter- and intra-rater reliability of the Silverman and Andersen index (SA index) among neonatologists and nurses when applied to preterm infants on respiratory support. We also examined the association between the SA index and the electrical activity of the diaphragm (Edi signals).

METHODS

This was a multicenter study including three newborn intensive care units in Norway. Four neonatologists and 10 nurses applied the SA index when assessing 80 videos of 44 preterm infants on High Flow Nasal Cannula, Continuous Positive Airway Pressure and Neurally Adjusted Ventilatory Assist. The inter- and intra-rater reliability for the sum scores were measured by the intra-class correlation coefficient (ICC), and Kendall's W was used to assess the degree of agreement for each item. We quantified the association between the Edi signals and the SA index scores by the Spearman's correlation coefficient.

RESULTS

We found poor inter-rater reliability with an ICC for absolute agreement of 0.34 (95% CI: 0.20 to 0.53). There was fair agreement measuring each item separately for upper chest movements (Kendall's W 0.30), and moderate for lower chest movements (0.43) and xiphoid retractions (0.44). Expiratory grunting showed substantial agreement (0.67). The intra-rater reliability was good (ICC for absolute agreement 0.77; 95% CI: 0.68 to 0.84). We found a moderate positive correlation (r = 0.468, p = 0.028) between the maximum inspiratory diaphragm activity (Edi peak) and the mean inspiratory SA index scores.

CONCLUSION

Our study showed poor inter-rater and good intra-rater reliability of the SA index when nurses and neonatologists assessed videos of preterm infants on various types of respiratory support. Edi peak and SA index had a moderate positive correlation. Formal training might be essential to improve the inter-rater reliability.

TRIAL REGISTRATION

Registered 26th June 2017, ClinicalTrials.gov Identifier: NCT03199898.

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.

Reference values for diaphragm electrical activity (Edi) in newborn infants

Background

Neurally adjusted ventilatory assist is an emerging mode of respiratory support that uses the electrical activity of the diaphragm (Edi) to provide synchronised inspiratory pressure support, proportional to an infant’s changing inspiratory effort. Data on Edi reference values for neonates are limited. The objective of this study was to establish reference Edi values for preterm and term neonates who are not receiving respiratory support.

Methods

This was a prospective observational study of newborn infants breathing spontaneously in room air. The Edi waveform was monitored by a specialised naso/orogastric feeding tube with embedded electrodes positioned at the level of the diaphragm. Edi minimums and peaks were recorded continuously for 4 h without changes to routine clinical handling.

Results

Twenty-four newborn infants (16 preterm [< 37 weeks’ gestation]; 8 term) were studied. All infants were breathing comfortably in room air at the time of study. Edi data were successfully captured in all infants. The mean (±SD) Edi minimum was 3.02 (±0.94) μV and the mean Edi peak was 10.13 (±3.50) μV. In preterm infants the mean (±SD) Edi minimum was 3.05 (±0.91) μV and the mean Edi peak was 9.36 (±2.13) μV. In term infants the mean (±SD) Edi minimum was 2.97 (±1.05) μV and the mean Edi peak was 11.66 (±5.14) μV.

Conclusion

Reference Edi values were established for both preterm and term neonates. These values can be used as a guide when monitoring breathing support and when using diaphragm-triggered modes of respiratory support in newborn infants

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03619-1.

Cardiorespiratory measures shortly after extubation and extubation outcomes in extremely preterm infants

BACKGROUND

Nasal continuous positive airway pressure, nasal intermittent positive pressure ventilation, and non-invasive neurally adjusted ventilatory assist are modes of non-invasive respiratory support. The objective was to investigate if cardiorespiratory measures performed shortly after extubation are associated with extubation outcomes and predictors of extubation success.

METHODS

Randomized crossover trial of infants with birth weight (BW) ≤ 1250 g undergoing their first extubation. Shortly after extubation, electrocardiogram and electrical activity of the diaphragm (Edi) were recorded during 40 min on each mode. Measures of heart rate variability (HRV), diaphragmatic activity (Edi area, breath area and amplitude), and respiratory variability (RV) were computed on each mode and compared between infants with extubation success or failure (reintubation ≤ 7 days).

RESULTS

Twenty-three extremely preterm infants with median [IQR] gestational age 25.9 weeks [25.2-26.4] and BW 760 g [595-900] were included: 14 success and 9 failures. There were significant differences for HRV (very low-frequency power and sample entropy) and RV parameters (breath areas, amplitudes and expiratory times) between groups, with moderate strength (0.75-0.80 areas under ROC curves) in predicting success. Diaphragmatic activity measures were similar between groups.

CONCLUSIONS

In extremely preterm infants receiving non-invasive respiratory support shortly after extubation, several cardiorespiratory variability parameters were associated with successful extubation with moderate predictive accuracy.

IMPACT

Measures of cardiorespiratory variability, performed in extremely preterm infants while receiving NCPAP, NIPPV, and NIV-NAVA shortly after extubation, were significantly different between patients that succeeded or failed extubation. Cardiorespiratory variability measures had a moderate predictive accuracy for extubation success and can be potentially used as biomarkers, in recently extubated infants. Future investigations in this population may also consider including cardiorespiratory variability measures when assessing types of post-extubation respiratory support and promote individualized care.

Noninvasive Neurally Adjusted Ventilation in Postextubation Stabilization of Preterm Infants: A Randomized Controlled Study

OBJECTIVE

To compare the effects of noninvasive neurally adjusted ventilatory assist (NIV-NAVA) to nasal continuous positive airway pressure (NCPAP) in achieving successful extubation in preterm infants.

STUDY DESIGN

This prospective, single-center, randomized controlled trial enrolled preterm infants born at <30 weeks of gestation who received invasive ventilation. Participants were assigned at random to either NIV-NAVA or NCPAP after their first extubation from invasive ventilation. The primary outcome of the study was extubation failure within 72 hours of extubation. Electrical activity of the diaphragm (Edi) values were collected before extubation and at 1, 4, 12, and 24 hours after extubation.

RESULTS

A total of 78 infants were enrolled, including 35 infants in the NIV-NAVA group and 35 infants in the NCPAP group. Extubation failure within 72 hours of extubation was higher in the NCPAP group than in the NIV-NAVA group (28.6% vs 8.6%; P = .031). The duration of respiratory support and incidence of severe bronchopulmonary dysplasia were similar in the 2 groups. Peak and swing Edi values were comparable before and at 1 hour after extubation, but values at 4, 12, and 24 hours after extubation were lower in the NIV-NAVA group compared with the NCPAP group.

CONCLUSIONS

In the present trial, NIV-NAVA was more effective than NCPAP in preventing extubation failure in preterm infants.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02590757.

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 effects of NIV-NAVA, NIPPV, and NCPAP shortly after extubation in extremely preterm infants: A randomized crossover trial

OBJECTIVE

Investigate the cardiorespiratory effects of noninvasive neurally adjusted ventilatory assist (NIV-NAVA), nonsynchronized nasal intermittent positive pressure ventilation (NIPPV), and nasal continuous positive airway pressure (NCPAP) shortly after extubation.

HYPOTHESIS

Types of noninvasive pressure support and the presence of synchronization may affect cardiorespiratory parameters.

STUDY DESIGN

Randomized crossover trial.

PATIENT-SUBJECT SELECTION

Infants with birth weight (BW) 1250 g or under, undergoing their first planned extubation were randomly assigned to all three modes using a computer-generated sequence.

METHODOLOGY

Electrocardiogram and electrical activity of the diaphragm (Edi) were recorded for 30 min on each mode. Analysis of heart rate variability (HRV), diaphragmatic activity (Edi area, breath area, amplitude, inspiratory and expiratory times), and respiratory variability were compared between modes.

RESULTS

Twenty-three infants had full data recordings and analysis: Median (IQR) gestational age = 25.9 weeks (25.2-26.4), BW = 760 g (595-900), and postnatal age 7 (4-19) days. There were no differences in HRV between modes. A significantly reduced Edi area and breath amplitude, and increased coefficient of variation (CV) of breath amplitude were observed during NIV-NAVA and NIPPV compared to NCPAP. A higher proportion of assisted breaths (99% vs. 51%; p < .001) provided a higher mean airway pressure (MAP; 9.4 vs. 8.2 cmH₂ O; p = .002) with lower peak inflation pressures (PIPs; 14 vs. 16 cmH₂ O; p < .001) during NIV-NAVA compared to NIPPV.

CONCLUSIONS

NIV-NAVA and NIPPV applied shortly after extubation were associated with lower respiratory efforts and higher respiratory variability. These effects were more evident for NIV-NAVA where optimal patient-ventilator synchronization provided a higher MAP with lower PIPs.

Effects of heliox and non-invasive neurally adjusted ventilatory assist (NIV-NAVA) in preterm infants

Due to its unique properties, helium–oxygen (heliox) mixtures may provide benefits during non-invasive ventilation, however, knowledge regarding the effects of such therapy in premature infants is limited. This is the first report of heliox non-invasive neurally adjusted ventilatory assist (NIV-NAVA) ventilation applied in neonates born ≤ 32 weeks gestational age. After baseline NIV-NAVA ventilation with a standard mixture of air and oxygen, heliox was introduced for 3 h, followed by 3 h of air-oxygen. Heart rate, peripheral capillary oxygen saturation, cerebral oxygenation, electrical activity of the diaphragm (Edi) and selected ventilatory parameters (e.g., respiratory rate, peak inspiratory pressure) were continuously monitored. We found that application of heliox NIV-NAVA in preterm infants was feasible and associated with a prompt and significant decrease of Edi suggesting reduced respiratory effort, while all other parameters were stable throughout the study, and had similar values during heliox and air-oxygen ventilation. This therapy may potentially enhance the efficacy of non-invasive respiratory support in preterm neonates and reduce the number of infants progressing to ventilatory failure.

Proportional assist and neurally adjusted ventilation: Clinical knowledge and future trials in newborn infants

Different types of patient triggered ventilator modes have become the mainstay of ventilation in term and preterm newborn infants. Maintaining spontaneous breathing has allowed for earlier weaning and the additive effects of respiratory efforts combined with pre-set mechanical inflations have reduced mean airway pressures, both of which are important components in trying to avoid lung injury and promote normal lung development. New sophisticated modes of assisted ventilation have been developed during the last decades where the control of ventilator support is turned over to the patient. The ventilator detects the respiratory effort and adjusts ventilatory assistance proportionally to each phase of the respiratory cycle, thus enabling the patient to have full control of the start, the duration and the amount of ventilatory assistance. In this paper we will review the literature on the ventilatory modes of proportional assist ventilation and neurally adjusted ventilatory assistance, examine the different ways the signals are analyzed, propose future studies, and suggest ways to apply these modes in the clinical environment.

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.

Diaphragmatic activity and neural breathing variability during a 5-min endotracheal continuous positive airway pressure trial in extremely preterm infants

BACKGROUND

Extremely preterm infants are often exposed to endotracheal tube continuous positive airway pressure (ETT-CPAP) trials to assess extubation readiness. The effects of ETT-CPAP trial on their diaphragmatic activity (Edi) and breathing variability is unknown.

METHODS

Prospective observational study enrolling infants with birth weight ≤1250 g undergoing their first extubation attempt. Diaphragmatic activity, expressed as the absolute minimum (Edi min) and maximum values (Edi max), area under the Edi signal, and breath-by-breath analyses for breath areas, amplitudes, widths, and neural inspiratory and expiratory times, were analyzed during mechanical ventilation (MV) and ETT-CPAP. Neural breathing variability of each of these parameters was also calculated and compared between MV and ETT-CPAP.

RESULTS

Thirteen infants with median (interquartile range) birth weight of 800 g [610-920] and gestational age of 25.4 weeks [24.4-26.3] were included. Diaphragmatic activity significantly increased during ETT-CPAP when compared to MV:Edi max (44.2 vs. 38.1 μV), breath area (449 vs. 312 μV·s), and amplitude (10.12 vs. 7.46 μV). Neural breathing variability during ETT-CPAP was characterized by increased variability for amplitude and area under the breath, and decreased for breath time and width.

CONCLUSIONS

A 5-min ETT-CPAP in extremely preterm infants undergoing extubation imposed significant respiratory load with changes in respiratory variability.

IMPACT

ETT-CPAP trials are often used to assess extubation readiness in extremely preterm infants, but its effects upon their respiratory system are not well known. Diaphragmatic activity analysis demonstrated that these infants are able to mount an important response to a short trial. A 5-min trial imposed a significant respiratory load evidenced by increased diaphragmatic activity and changes in breathing variability. Differences in breathing variability were observed between successful and failed extubations, which should be explored further in extubation readiness investigations. This type of trial cannot be recommended for preterm infants in clinical practice until clear standards and accuracy are established.

Changes in pulmonary oxygen content are detectable with laser absorption spectroscopy: proof of concept in newborn piglets

BACKGROUND

Using an optical method based on tunable diode laser absorption spectroscopy, we previously assessed oxygen (O₂) and water vapor (H₂O) content in a tissue phantom of the preterm infant lung. Here we applied this method on newborn piglets with induced lung complications.

METHODS

Five mechanically ventilated piglets were subjected to stepwise increased and decreased fraction of inspired oxygen (FiO₂), to atelectasis using a balloon catheter in the right bronchus, and to pneumothorax by injecting air in the pleural cavity. Two diode lasers (764 nm for O₂ gas absorption and 820 nm for H₂O absorption) were combined in a probe delivering light either externally, on the skin, or internally, through the esophagus. The detector probe was placed dermally.

RESULTS

Calculated O₂ concentrations increased from 20% (IQR 17-23%) when ventilated with room air to 97% (88-108%) at FiO₂ 1.0. H₂O was only detectable with the internal light source. Specific light absorption and transmission patterns were identified in response to atelectasis and pneumothorax, respectively.

CONCLUSIONS

The optical method detected FiO₂ variations and discriminated the two induced lung pathologies, providing a rationale for further development into a minimally invasive device for real-time monitoring gas changes in the lungs of sick newborn infants.

IMPACT

Optical spectroscopy can detect pulmonary complications in an animal model. Oxygen concentrations can be evaluated in the lungs. Presents a novel minimally invasive method to detect lung oxygenation and complications. Potential to be developed into a lung monitoring method in newborn infants. Potential for bed-side detection of pulmonary complications in newborn infants.

Postnatal physiological changes in electrical activity of the diaphragm in extremely preterm infants

OBJECTIVES

This study aimed to describe postnatal physiological changes in maximum values of peak electrical activity of the diaphragm (Edi) in extremely preterm infants during the preterm period.

WORKING HYPOTHESIS

The amplitude and frequency of neural sigh are different at each postmenstrual age in extremely preterm infants.

STUDY DESIGN

A retrospective, observational study.

PATIENT-SUBJECT SELECTION

Edi values were evaluated in 14 extremely preterm infants with neurally-adjusted ventilatory assist.

METHODOLOGY

Data of Edi peak and Edi minimum were collected from a ventilator. Edi-sigh was defined as the Edi peak value that was more than twice as large as the median Edi peak at each postmenstrual week in each patient. The frequency of Edi-sigh, and median values of Edi-sigh, Edi peak, and Edi minimum were evaluated at each postmenstrual week. The Jonckheere-Terpstra test was used to analyze the trend between postmenstrual weeks and Edi values.

RESULTS

From 26 to 35 postmenstrual weeks, the number of Edi-sighs per hour significantly increased as postmenstrual weeks increased (P < .001). Furthermore, the median values of Edi-sigh significantly increased as postmenstrual weeks increased (16.9 µV at 26 weeks to 25.4 µV at 35 weeks, P < .001). There were no significant changes in the median values of Edi peak and Edi minimum at each week.

CONCLUSIONS

The amplitude and frequency of neural sigh in extremely preterm infants increase with the number of postmenstrual weeks.

A randomised cross-over study showed no difference in diaphragm activity during weaning from respiratory support

AIM

We measured electrical activity of the diaphragm (Edi) to compare the breathing effort in preterm infants during weaning from respiratory support with high-flow nasal cannulae (HFNC) or nasal continuous positive airway pressure (nCPAP).

METHODS

This randomised cross-over study was carried out at St Olav's University Hospital, Trondheim, Norway, from December 2013 to June 2015. We gave 21 preterm infants weighing at least 1000 g HFNC 6 L/minute for four hours and nCPAP 3 cmH₂ O for four hours with a one-hour wash-out period. Measurements included diaphragmatic load, Edi, vital signs and a modified Silverman-Andersen Retraction Score.

RESULTS

We found no differences in HFNC and nCPAP in the median Edi peak (8.0 μV versus 7.8 μV, p = 0.095), median Edi min (1.1 μV versus 1.2 μV in, p = 0.958) or mean heart rate (157 versus 159, p = 0.300) in the 21 infants who took part. The mean respiratory rate was significantly lower during HFNC than nCPAP (47 versus 52, p = 0.012). The modified Silverman-Andersen Retraction Score showed no significant differences.

CONCLUSION

This study of preterm infants found no difference in the breathing effort measured by Edi between HFNC 6 L/minute and nCPAP 3 cmH₂ O. HFNC could replace nCPAP when preterm infants are ready for weaning.

Neurally Adjusted Ventilatory Assist for Noninvasive Support in Neonates

Noninvasive ventilation (NIV) is frequently used in the NICU to avoid intubation or as postextubation support for spontaneously breathing infants experiencing respiratory distress. Neurally adjusted ventilatory assist (NAVA) is used as a mode of noninvasive support in which both the timing and degree of ventilatory assist are controlled by the patient. NIV-NAVA has been successfully used clinically in neonates as a mode of ventilation to prevent intubation, allow early extubation, and as a novel way to deliver nasal continuous positive airway pressure.

Impact of feeding method on diaphragm electrical activity and central apnea in preterm infants (FEAdi study)

BACKGROUND

In preterm infants, it is unknown whether feeding affects neural breathing pattern.

OBJECTIVES

By measuring the diaphragm electrical activity (Edi) waveform, we evaluated the effect of enteral feeding and compared the effects of feeding methods on neural breathing pattern and central apnea in very low birth weight preterm infants.

METHODS

In a prospective, randomized, crossover study, ten non-ventilated preterm infants with birth weights<1250g and tolerating full feeds were randomized to either bolus feeding (BF) or slow infusion feeding (SF) over 90min, followed by crossover to the other method at the next feed. Edi was continuously measured by a feeding catheter with miniaturized sensors. Five 15-min epochs were chosen [Baseline (BL), first 15min and 90min after BF/SF started] for breath-by-breath analyses of neural breathing pattern, including Edi peak, Edi min (end-expiratory), neural inspiratory and expiratory times, neural respiratory rate, and central apnea. Primary outcome was change in Edi min with feed. Secondary outcomes include change in Edi peak, frequency and duration of central apnea with feeding.

RESULTS

Although intrasubject coefficient of variation was not significantly different, individual responses to feeding and feeding method were variable. No significant difference in Edi timing, Edi min, Edi peak, or apnea was observed for the different epochs.

CONCLUSIONS

In this study cohort, neural breathing pattern does not appear to be consistently affected by enteral feeding or the feeding method. Compared with BF, SF does not appear to reduce the number or duration of apneas.

Non-invasive ventilation with neurally adjusted ventilatory assist in newborns

Neurally adjusted ventilatory assist (NAVA) is a mode of ventilation in which both the timing and degree of ventilatory assist are controlled by the patient. Since NAVA uses the diaphragm electrical activity (Edi) as the controller signal, it is possible to deliver synchronized non-invasive NAVA (NIV-NAVA) regardless of leaks and to monitor continuously patient respiratory pattern and drive. Advantages of NIV-NAVA over conventional modes include improved patient-ventilator interaction, reliable respiratory monitoring and self-regulation of respiratory support. In theory, these characteristics make NIV-NAVA an ideal mode to provide effective, appropriate non-invasive support to newborns with respiratory insufficiency. NIV-NAVA has been successfully used clinically in neonates as a mode of ventilation to prevent intubation, to allow early extubation, and as a novel way to deliver nasal continuous positive airway pressure. The use of NAVA in neonates is described with an emphasis on studies and clinical experience with NIV-NAVA.

High-flow nasal cannulae are associated with increased diaphragm activation compared with nasal continuous positive airway pressure in preterm infants

AIM

High-flow nasal cannulae (HFNC) are increasingly used for respiratory management of preterm infants. However, their ability to provide support compared to nasal continuous positive airway pressure (CPAP) has been questioned. We compared the effect of HFNC versus nasal CPAP on diaphragm electrical activity (EAdi) in preterm infants.

METHODS

Preterm infants ≤1500 g were randomised in a crossover design to receive 2 hours of either Infant Flow(®) CPAP (IF-CPAP) at 5-6 cmH2 O or HFNC with the flow rate adjusted to achieve an equivalent pharyngeal pressure. A feeding catheter with miniaturised sensors was inserted for continuous EAdi measurement.

RESULTS

The study comprised ten infants. Physiologic parameters and oxygen requirements were not different between the two modes. However, seven infants demonstrated a higher EAdi peak and six showed a higher EAdi tonic on HFNC, even though the mean group data showed no difference between HFNC and IF-CPAP. Neural inspiratory time was significantly longer with HFNC than IF-CPAP (0.55 ± 0.11 versus 0.48 ± 0.06 seconds, p = 0.018).

CONCLUSION

In this cohort of preterm infants, the majority exhibited greater diaphragm activation, as assessed by neural breathing patterns, when supported with HFNC than IF-CPAP, suggesting that nasal CPAP may provide more effective respiratory support.

Evolution of inspiratory diaphragm activity in children over the course of the PICU stay

PURPOSE

Diaphragm function should be monitored in critically ill patients, as full ventilatory support rapidly induces diaphragm atrophy. Monitoring the electrical activity of the diaphragm (EAdi) may help assess the level of diaphragm activity, but such monitoring results are difficult to interpret because reference values are lacking. The aim of this study was to describe EAdi values in critically ill children during a stay in the pediatric intensive care unit (PICU), from the acute to recovery phases, and to assess the impact of ventilatory support on EAdi.

METHODS

This was a prospective longitudinal observational study of children requiring mechanical ventilation for ≥24 h. EAdi was recorded using a validated method in the acute phase, before extubation, after extubation, and before PICU discharge.

RESULTS

Fifty-five critically ill children were enrolled in the study. Median maximum inspiratory EAdi (EAdimax) during mechanical ventilation was 3.6 [interquartile range (IQR) 1.2-7.6] μV in the acute phase and 4.8 (IQR 2.0-10.7) μV in the pre-extubation phase. Periods of diaphragm inactivity (with no detectable inspiratory EAdi) were frequent during conventional ventilation, even with a low level of support. EAdimax in spontaneous ventilation was 15.4 (IQR 7.4-20.7) μV shortly after extubation and 12.6 (IQR 8.1-21.3) μV before PICU discharge. The difference in EAdimax between mechanical ventilation and post-extubation periods was significant (p < 0.001). Patients intubated mainly because of a lung pathology exhibited higher EAdi (p < 0.01), with a similar temporal increase.

CONCLUSIONS

This is the first systematic description of EAdi evolution in children during their stay in the PICU. In our patient cohort, diaphragm activity was frequently low in conventional ventilation, suggesting that overassistance or oversedation is common in clinical practice. EAdi monitoring appears to be a helpful tool to detect such situations.

Application of neurally adjusted ventilatory assist in neonates

Neurally adjusted ventilatory assist (NAVA) uses the electrical activity of the diaphragm (Edi) as a neural trigger to synchronize mechanical ventilatory breaths with the patient's neural respiratory drive. Using this signal enables the ventilator to proportionally support the patient's instantaneous drive on a breath-by-breath basis. Synchrony can be achieved even in the presence of significant air leaks, which make this an attractive choice for invasive and non-invasive ventilation of the neonate. This paper describes the Edi signal, neuroventilatory coupling, and patient-ventilator synchrony including the functional concept of NAVA. Safety features, NAVA terminology, and clinical application of NAVA to unload respiratory musculature are presented. The use of the Edi signal as a respiratory vital sign for conventional ventilation is discussed. The results of animal and adult studies are briefly summarized and detailed descriptions of all NAVA-related research in pediatric and neonatal patients are provided. Further studies are needed to determine whether NAVA will have significant impact on the overall outcomes of neonates.