Interest of monitoring diaphragmatic electrical activity in the pediatric intensive care unit

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.

A narrative review of diaphragmatic ultrasound in pediatric critical care

The use of point of care ultrasound (POCUS) at the bedside has increased dramatically within emergency medicine and in critical care. Applications of POCUS have spread to include diaphragmatic assessments in both adults and children. Diaphragm POCUS can be used to assess for diaphragm dysfunction (DD) and atrophy or to guide ventilator titration and weaning. Quantitative, semi-quantitative and qualitative measurements of diaphragm thickness, diaphragm excursion, and diaphragm thickening fraction provide objective data related to DD and atrophy. The potential for quick, noninvasive, and repeatable bedside diaphragm assessments has led to a growing amount of literature on diaphragm POCUS. To date, there are no reviews of the current state of diaphragm POCUS in pediatric critical care. The aims of this narrative review are to summarize the current literature regarding techniques, reference values, applications, and future innovations of diaphragm POCUS in critically ill children. A summary of current practice and future directions will be discussed.

Neurally-Adjusted Ventilatory Assist (NAVA) versus Pneumatically Synchronized Ventilation Modes in Children Admitted to PICU

Traditionally, invasively ventilated children in the paediatric intensive care unit (PICU) are weaned using pneumatically-triggered ventilation modes with a fixed level of assist. The best weaning mode is currently not known. Neurally adjusted ventilatory assist (NAVA), a newer weaning mode, uses the electrical activity of the diaphragm (Edi) to synchronise ventilator support proportionally to the patient’s respiratory drive. We aimed to perform a systematic literature review to assess the effect of NAVA on clinical outcomes in invasively ventilated children with non-neonatal lung disease. Three studies (n = 285) were included for analysis. One randomised controlled trial (RCT) of all comers showed a significant reduction in PICU length of stay and sedative use. A cohort study of acute respiratory distress syndrome (ARDS) patients (n = 30) showed a significantly shorter duration of ventilation and improved sedation with the use of NAVA. A cohort study of children recovering from cardiac surgery (n = 75) showed significantly higher extubation success, shorter duration of ventilation and PICU length of stay, and a reduction in sedative use. Our systematic review presents weak evidence that NAVA may shorten the duration of ventilation and PICU length of stay, and reduce the requirement of sedatives. However, further RCTs are required to more fully assess the effect of NAVA on clinical outcomes and treatment costs in ventilated children.

Evolution of inspiratory muscle function in children during mechanical ventilation

BACKGROUND

There is no universally accepted method to assess the pressure-generating capacity of inspiratory muscles in children on mechanical ventilation (MV), and no study describing its evolution over time in this population.

METHODS

In this prospective observational study, we have assessed the function of the inspiratory muscles in children on various modes of MV. During brief airway occlusion maneuvers, we simultaneously recorded airway pressure depression at the endotracheal tube (ΔPaw, force generation) and electrical activity of the diaphragm (EAdi, central respiratory drive) over five consecutive inspiratory efforts. The neuro-mechanical efficiency ratio (NME, ΔPaw/EAdimax) was also computed. The evolution over time of these indices in a group of children in the pediatric intensive care unit (PICU) was primarily described. As a secondary objective, we compared these values to those measured in a group of children in the operating room (OR).

RESULTS

In the PICU group, although median NMEoccl decreased over time during MV (regression coefficient - 0.016, p = 0.03), maximum ΔPawmax remained unchanged (regression coefficient 0.109, p = 0.50). Median NMEoccl at the first measurement in the PICU group (after 21 h of MV) was significantly lower than at the only measurement in the OR group (1.8 cmH2O/µV, Q1-Q3 1.3-2.4 vs. 3.7 cmH2O/µV, Q1-Q3 3.5-4.2; p = 0.015). Maximum ΔPawmax in the PICU group was, however, not significantly different from the OR group (35.1 cmH2O, Q1-Q3 21-58 vs. 31.3 cmH2O, Q1-Q3 28.5-35.5; p = 0.982).

CONCLUSIONS

The function of inspiratory muscles can be monitored at the bedside of children on MV using brief airway occlusions. Inspiratory muscle efficiency was significantly lower in critically ill children than in children undergoing elective surgery, and it decreased over time during MV in critically ill children. This suggests that both critical illness and MV may have an impact on inspiratory muscle efficiency.

Utilization of Neurally Adjusted Ventilatory Assist (NAVA) Mode in Infants and Children Undergoing Congenital Heart Surgery: A Retrospective Review

We assessed the feasibility and the impact of NAVA compared to conventional modes of mechanical ventilation in ventilatory and gas exchange parameters in post-operative children with congenital heart disease. Infants and children (age < 18 years) that underwent congenital heart surgery were enrolled. Patients were ventilated with conventional synchronized intermittent mechanical ventilation (SIMV) and subsequently transitioned to NAVA during their cardiovascular intensive care unit (CVICU) stay. The ventilatory and gas exchange parameters for the 24 h pre- and post-transition to NAVA were compared. Additional parameters assessed included pain scores and sedation requirements. Eighty-one patients met inclusion criteria with a median age of 21 days (interquartile range 13 days-2 months). The majority of patients enrolled (75.3%) had complex congenital heart disease with high surgical severity scores. The transition to NAVA was tolerated by all patients without complications. The mean peak inspiratory pressure (PIP) was 1.8 cm H₂O lower (p < 0.001) and mean airway pressure (P_aw) was 0.5 cm H₂O lower (p = 0.009) on NAVA compared to conventional modes of mechanical ventilation. There was no significant difference in patients' respiratory rate, tidal volume, arterial pH, pCO₂, and lactate levels between the two modes of ventilation. There was a decreased sedation requirement during the time of NAVA ventilation. Comfort scores did not differ significantly with ventilator mode change. We concluded that NAVA is safe and well-tolerated mode of mechanical ventilation for our cohort of patients after congenital heart surgery. Compared to conventional ventilation there was a statistically significant decrease in PIP and P_aw on NAVA.

Patient-ventilator asynchrony during conventional mechanical ventilation in children

Background

We aimed (1) to describe the characteristics of patient–ventilator asynchrony in a population of critically ill children, (2) to describe the risk factors associated with patient–ventilator asynchrony, and (3) to evaluate the association between patient–ventilator asynchrony and ventilator-free days at day 28.

Methods

In this single-center prospective study, consecutive children admitted to the PICU and mechanically ventilated for at least 24 h were included. Patient–ventilator asynchrony was analyzed by comparing the ventilator pressure curve and the electrical activity of the diaphragm (Edi) signal with (1) a manual analysis and (2) using a standardized fully automated method.

Results

Fifty-two patients (median age 6 months) were included in the analysis. Eighteen patients had a very low ventilatory drive (i.e., peak Edi < 2 µV on average), which prevented the calculation of patient–ventilator asynchrony. Children spent 27% (interquartile 22–39%) of the time in conflict with the ventilator. Cycling-off errors and trigger delays contributed to most of this asynchronous time. The automatic algorithm provided a NeuroSync index of 45%, confirming the high prevalence of asynchrony. No association between the severity of asynchrony and ventilator-free days at day 28 or any other clinical secondary outcomes was observed, but the proportion of children with good synchrony was very low.

Conclusion

Patient–ventilator interaction is poor in children supported by conventional ventilation, with a high frequency of depressed ventilatory drive and a large proportion of time spent in asynchrony. The clinical benefit of strategies to improve patient–ventilator interactions should be evaluated in pediatric critical care.

Recent Advances in Pediatric Ventilatory Assistance

In this review on respiratory assistance, we aim to discuss the following recent advances: the optimization and customization of mechanical ventilation, the use of high-frequency oscillatory ventilation, and the role of noninvasive ventilation. The prevention of ventilator-induced lung injury and diaphragmatic dysfunction is now a key aspect in the management of mechanical ventilation, since these complications may lead to higher mortality and prolonged length of stay in intensive care units. Different physiological measurements, such as esophageal pressure, electrical activity of the diaphragm, and volumetric capnography, may be useful objective tools to help guide ventilator assistance. Companies that design medical devices including ventilators and respiratory monitoring platforms play a key role in knowledge application. The creation of a ventilation consortium that includes companies, clinicians, researchers, and stakeholders could be a solution to promote much-needed device development and knowledge implementation.

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.

Neurally adjusted ventilator assist (NAVA) reduces asynchrony during non-invasive ventilation for severe bronchiolitis

BACKGROUND

To determine the prevalence of main inspiratory asynchrony events during non-invasive intermittent positive-pressure ventilation (NIV) for severe bronchiolitis. Ventilator response time and asynchrony were compared in neurally adjusted ventilator assist (NAVA) and in pressure assist/control (PAC) modes.

METHODS

This prospective physiological study was performed in a university hospital's paediatric intensive care unit and included 11 children (aged 35.2 ± 23 days) with respiratory syncytial virus bronchiolitis with failure of nCPAP. Patients received NIV for 2 hr in PAC mode followed by 2 hr in NAVA mode. Electrical activity of the diaphragm and pressure curves were recorded for 10 min. Trigger delay, main asynchronies (auto-triggering, double triggering, or non-triggered breaths) were analyzed, and the asynchrony index was calculated for each period.

RESULTS

The asynchrony index was lower during NAVA than during PAC (3 ± 3% vs. 38 ± 21%, P < 0.0001), and the trigger delay was shorter (43.9 ± 7.2 vs. 116.0 ± 38.9 ms, P < 0.0001). Ineffective efforts were significantly less frequent in NAVA mode (0.54 ± 1.5 vs. 21.8 ± 16.5 events/min, P = 0.01). Patient respiratory rates were similar, but the ventilator rate was higher in NAVA than in PAC mode (59.5 ± 17.9 vs. 49.8 ± 8.5/min, P = 0.03). The TcPCO2 baselines values (64 ± 12 mmHg vs. 62 ± 9 mmHg during NAVA, P = 0.30) were the same and their evolution over the 2 hr study period (-6 ± 10 mmHg vs. -12 ± 17 mmHg during NAVA, P = 0.36) did not differ.

CONCLUSION

Patient-ventilator inspiratory asynchronies and trigger delay were dramatically lower in NAVA mode than in PAC mode during NIV in infants with severe bronchiolitis.

Assessing the Response to Inhaled Albuterol by Monitoring Patient Effort-Related Trends With a Servo-I Ventilator in Neurally Adjusted Ventilatory Assist Mode: A Case Presentation

BACKGROUND

Infants with chronic lung disease tend to be difficult to care for due to the heterogeneous nature of both their disease and the treatments required. Multiple types of medications, treatments, and nursing interventions are often needed to attain clinical success, and it is frequently difficult to discern which are effective versus the ones that offer no benefit. This article presents a case study that chronicles the care of an infant with chronic lung disease treated with albuterol. An innovative form of ventilation with monitoring of the electrical activity of the diaphragm with a special sensor-embedded catheter is used to assess the effectiveness of albuterol administration.

PURPOSE

This case study presents the monitoring of the effectiveness of albuterol in an infant with chronic lung disease measuring the electrical activity of the diaphragm catheter (Edi) and the various monitoring systems on the Servo-i ventilator in Neurally Adjusted Ventilatory Assist (NAVA) Mode.

CASE FINDINGS/RESULTS

The clinicians followed various respiratory trends monitored by the Servo-i ventilator after albuterol dosing to document the clinical utility of using albuterol in this infant. The monitoring provided by NAVA showed an improvement in both lung mechanics and clinical condition immediately after albuterol administration.

IMPLICATIONS FOR PRACTICE

The infant had a positive response to albuterol dosing that subsequently led to reduced length of stay, reduced costs, and reduced family anxiety. This type of monitoring could help nurses and clinicians discern whether a given treatment or medication was effective.

IMPLICATIONS FOR RESEARCH

This method of clinical monitoring could provide a means to assess clinical utility of respiratory medications, treatments, and nursing interventions in certain populations of neonates and infants. The impact of objective monitoring on required sedation, weight gain, ventilator days, length of hospitalization, and overall hospital costs are other possible areas for future research.

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.

Impact of ventilatory modes on the breathing variability in mechanically ventilated infants

OBJECTIVES

Reduction of breathing variability is associated with adverse outcome. During mechanical ventilation, the variability of ventilatory pressure is dependent on the ventilatory mode. During neurally adjusted ventilatory assist (NAVA), the support is proportional to electrical activity of the diaphragm (EAdi), which reflects the respiratory center output. The variability of EAdi is, therefore, translated into a similar variability in pressures. Contrastingly, conventional ventilatory modes deliver less variable pressures. The impact of the mode on the patient's own respiratory drive is less clear. This study aims to compare the impact of NAVA, pressure-controlled ventilation (PCV), and pressure support ventilation (PSV) on the respiratory drive patterns in infants. We hypothesized that on NAVA, EAdi variability resembles most of the endogenous respiratory drive pattern seen in a control group.

METHODS

Electrical activity of the diaphragm was continuously recorded in 10 infants ventilated successively on NAVA (5 h), PCV (30 min), and PSV (30 min). During the last 10 min of each period, the EAdi variability pattern was assessed using non-rhythmic to rhythmic (NRR) index. These variability profiles were compared to the pattern of a control group of 11 spontaneously breathing and non-intubated infants.

RESULTS

In control infants, NRR was higher as compared to mechanically ventilated infants (p < 0.001), and NRR pattern was relatively stable over time. While the temporal stability of NRR was similar in NAVA and controls, the NRR profile was less stable during PCV. PSV exhibited an intermediary pattern.

PERSPECTIVES

Mechanical ventilation impacts the breathing variability in infants. NAVA produces EAdi pattern resembling most that of control infants. NRR can be used to characterize respiratory variability in infants. Larger prospective studies are necessary to understand the differential impact of the ventilatory modes on the cardio-respiratory variability and to study their impact on clinical outcomes.