Guillaume Emeriaud

Prolonged neural expiratory time induced by mechanical ventilation in infants.

Mechanical ventilation may interfere with the spontaneous breathing pattern in infants because they have strong reflexes that play a large role in the control of breathing. This study aimed to answer the following questions: does a ventilator-assisted breath 1) reduce neural inspiratory time, 2) reduce the amplitude of the diaphragm electrical activity, and 3) prolong neural expiration, within the delivered breath? In 14 infants recovering from acute respiratory failure (mean age and weight were 2.3 ± 1.3 mo and 3.95 ± 0.82 kg, respectively), we measured 1) the electrical activity of the diaphragm with a multiple-array esophageal electrode, and 2) airway opening pressure, while patients breathed on synchronized intermittent mandatory ventilation (mean rate, 11.2 ± 6.5 breaths/min). We compared neural inspiratory and expiratory times for the mandatory breaths and for the spontaneous breaths immediately preceding and following the mandatory breath. Although neural inspiratory time was not different between mandatory and spontaneous breaths, neural expiratory time was significantly increased (p < 0.001) for the mandatory breaths (953 ± 449 ms) compared with the premandatory and postmandatory spontaneous breaths (607 ± 268 ms and 560 ± 227 ms, respectively). Delivery of the mandatory breath resulted in a reduction in neural respiratory frequency by 28.6 ± 6.4% from the spontaneous premandatory frequency. The magnitude of inspiratory electrical activity of the diaphragm was similar for all three breath conditions. For the mandatory breaths, ventilatory assist persisted for 507 ± 169 ms after the end of neural inspiratory time. Infant–ventilator asynchrony (both inspiratory and expiratory asynchrony) was present in every mandatory breath and constituted 53.4 ± 26.2% of the total breath duration.

Diaphragm Electrical Activity During Expiration in Mechanically Ventilated Infants

The presence of diaphragm electrical activity (EAdi) during expiration is believed to be involved in the maintenance of end-expiratory lung volume (EELV) and has never been studied in intubated and mechanically ventilated infants. The aim of this study was to quantify the amplitude of diaphragm electrical activity present during expiration in mechanically ventilated infants and to measure the impact of removing positive end-expiratory pressure (PEEP) on this activity. We studied the EAdi in 16 ready-to-be weaned intubated infants who were breathing on their prescribed ventilator and PEEP settings. In all 16 patients, 5 min of data were collected on the prescribed ventilator settings. In a subset of eight patients, the PEEP was briefly reduced to zero PEEP (ZEEP). EAdi was recorded with miniaturized sensors placed on a conventional nasogastric feeding tube. Airway pressure (Paw) was also measured. For each spontaneous breath, we identified the neural inspiration and neural expiration. Neural expiration was divided into quartiles (Q1, Q2, Q3, and Q4), and the amplitude of EAdi calculated for each Q1–Q4 represented 95 ± 29%, 31 ± 15%, 15 ± 8%, and 12 ± 7%, respectively, of the inspiratory EAdi amplitude. EAdi for Q3–Q4 significantly increased during ZEEP, and decreased after reapplication of PEEP. These findings confirm that the diaphragm remains partially active during expiration in intubated and mechanically ventilated infants and that removal of PEEP affects this tonic activity. This could have potential implications on the management of PEEP in intubated infants.

Fetal lung volume in congenital diaphragmatic hernia

In a retrospective study of 22 neonates with congenital diaphragmatic hernia, fetal lung volume (FLV) measured by magnetic resonance imaging was associated with survival; the best FLV ratio cut-off to predict mortality was 30% of expected FLV. This study supports a correlation between FLV and the chances of survival.

Neurally adjusted ventilatory assist improves patient–ventilator interaction in infants as compared with conventional ventilation

Background:Neurally adjusted ventilatory assist (NAVA) is a mode of ventilation controlled by the electrical activity of the diaphragm (Edi). The aim was to evaluate patient–ventilator interaction in infants during NAVA as compared with conventional ventilation.Methods:Infants were successively ventilated with NAVA, pressure control ventilation (PCV), and pressure support ventilation (PSV). Edi and ventilator pressure (Pvent) waveforms were compared and their variability was assessed by coefficients of variation.Results:Ten patients (mean age 4.3 ± 2.4 mo and weight 5.9 ± 2.2 kg) were studied. In PCV and PSV, 4 ± 4.6% and 6.5 ± 7.7% of the neural efforts failed to trigger the ventilator. This did not occur during NAVA. Trigger delays were shorter with NAVA as compared with PCV and PSV (93 ± 20 ms vs. 193 ± 87 ms and 135 ± 29 ms). During PCV and PSV, the ventilator cycled off before the end of neural inspiration in 12 ± 13% and 21 ± 19% of the breaths (0 ± 0% during NAVA). During PCV and PSV, 24 ± 11% and 25 ± 9% of the neural breath cycle was asynchronous with the ventilator as compared with 11 ± 3% with NAVA. A large variability was observed for Edi in all modes, which was transmitted into Pvent during NAVA (coefficient of variation: 24 ± 8%) and not in PCV (coefficient of variation 2 ± 1%) or PSV (2 ± 2%).Conclusion:NAVA improves patient–ventilator interaction and delivers adequate ventilation with variable pressure in infants.

Site-level variance for adverse tracheal intubation-associated events across 15 North American PICUs: a report from the national emergency airway registry for children*.

Objective: Tracheal intubation in PICUs is associated with adverse tracheal intubation–associated events. Patient, provider, and practice factors have been associated with tracheal intubation–associated events; however, site-level variance and the association of site-level characteristics on tracheal intubation–associated event outcomes are unknown. We hypothesize that site-level variance exists in the prevalence of tracheal intubation–associated events and that site characteristics may affect outcomes. Design: Prospective observational cohort study. Setting: Fifteen PICUs in North America. Subjects: Critically ill pediatric patients requiring tracheal intubation. Interventions: None. Measurement and Main Results: Tracheal intubation quality improvement data were collected in 15 PICUs from July 2010 to December 2011 using a National Emergency Airway Registry for Children with robust site-specific compliance. Tracheal intubation–associated events and severe tracheal intubation–associated events were explicitly defined a priori. We analyzed the association of site-level variance with tracheal intubation–associated events using univariate analysis and adjusted for previously identified patient- and provider-level risk factors. Analysis of 1,720 consecutive intubations revealed an overall prevalence of 20% tracheal intubation–associated events and 6.5% severe tracheal intubation–associated events, with considerable site variability ranging from 0% to 44% tracheal intubation–associated events and from 0% to 20% severe tracheal intubation–associated events. Larger PICU size (> 26 beds) was associated with fewer tracheal intubation–associated events (18% vs 23%, p = 0.006), but the presence of a fellowship program was not (20% vs 18%, p = 0.58). After adjusting for patient and provider characteristics, both PICU size and fellowship presence were not associated with tracheal intubation–associated events (p = 0.44 and p = 0.18, respectively). Presence of mixed ICU with cardiac surgery was independently associated with a higher prevalence of tracheal intubation–associated events (25% vs 15%; p < 0.001; adjusted odds ratio, 1.81; 95% CI, 1.29–2.53; p = 0.01). Substantial site-level variance was observed in medication use, which was not explained by patient characteristic differences. Conclusions: Substantial site-level variance exists in tracheal intubation practice, tracheal intubation–associated events, and severe tracheal intubation–associated events. Neither PICU size nor fellowship training program explained site-level variance. Interventions to reduce tracheal intubation–associated event prevalence and severity will likely need to be contextualized to variability in individual ICUs patients, providers, and practice.

Interest of Monitoring Diaphragmatic Electrical Activity in the Pediatric Intensive Care Unit

The monitoring of electrical activity of the diaphragm (EAdi) is a new minimally invasive bedside technology that was developed for the neurally adjusted ventilatory assist (NAVA) mode of ventilation. In addition to its role in NAVA ventilation, this technology provides the clinician with previously unavailable and essential information on diaphragm activity. In this paper, we review the clinical interests of EAdi in the pediatric intensive care setting. Firstly, the monitoring of EAdi allows the clinician to tailor the ventilatory settings on an individual basis, avoiding frequent overassistance leading potentially to diaphragmatic atrophy. Increased inspiratory EAdi levels can also suggest insufficient support, while a strong tonic activity may reflect the patient efforts to increase its lung volume. EAdi monitoring also allows detection of patient-ventilator asynchrony. It can play a role in evaluation of extubation readiness. Finally, EAdi monitoring provides the clinician with better understanding of the ventilatory capacity of patients with acute neuromuscular disease. Further studies are warranted to evaluate the clinical impact of these potential benefits.

Calibration of respiratory inductance plethysmograph in preterm infants with different respiratory conditions

Respiratory inductance plethysmography (RIP) is a method for respiratory measurements particularly attractive in infants because it is noninvasive and it does not interfere with the airway. RIP calibration remains controversial in neonates, and is particularly difficult in infants with thoraco-abdominal asynchrony or with ventilatory assist. The objective of this study was to evaluate a new RIP calibration method in preterm infants either without respiratory disease, with thoraco-abdominal asynchrony, or with ventilatory support. This method is based on (i) a specifically adapted RIP jacket, (ii) the least squares method to estimate the volume/motion ribcage and abdominal coefficients, and (iii) an individualized filtering method that takes into account individual breathing pattern. The reference flow was recorded with a pneumotachograph. The accuracy of flow reconstruction using the new method was compared to the accuracy of three other calibration methods, with arbitrary fixed RIP coefficients or with coefficients determined according to qualitative diagnostic calibration method principle. Fifteen preterm neonates have been studied; gestational age was (mean +/- SD) 31.7 +/- 0.8 weeks; birth weight was 1,470 +/- 250 g. The respiratory flow determined with the new method had a goodness of fit at least equivalent to the other three methods in the entire group. Moreover, in unfavorable conditions--breathing asynchrony or ventilatory assist--the quality of fit was significantly higher than with the three other methods (P < 0.05, repeated measures ANOVA). Accuracy of tidal volume measurements was at least equivalent to the other methods, and the breath-by-breath differences with reference volumes were lower, although not significantly, than with the other methods. The goodness of fit of the reconstructed RIP flow with this new method--even in unfavorable respiratory conditions--provides a prerequisite for the study of flow pattern during the neonatal period.

The critically-ill pediatric hemato-oncology patient: epidemiology, management, and strategy of transfer to the pediatric intensive care unit

Cancer is a leading cause of death in children. In the past decades, there has been a marked increase in overall survival of children with cancer. However, children whose treatment includes hematopoietic stem cell transplantation still represent a subpopulation with a higher risk of mortality. These improvements in mortality are accompanied by an increase in complications, such as respiratory and cardiovascular insufficiencies as well as neurological problems that may require an admission to the pediatric intensive care unit where most supportive therapies can be provided. It has been shown that ventilatory and cardiovascular support along with renal replacement therapy can benefit pediatric hemato-oncology patients if promptly established. Even if admissions of these patients are not considered futile anymore, they still raise sensitive questions, including ethical issues. To support the discussion and potentially facilitate the decision-making process, we propose an algorithm that takes into account the reason for admission (surgical versus medical) and the hemato-oncological prognosis. The algorithm then leads to different types of admission: full-support admission, “pediatric intensive care unit trial” admission, intensive care with adapted level of support, and palliative intensive care. Throughout the process, maintaining a dialogue between the treating physicians, the paramedical staff, the child, and his parents is of paramount importance to optimize the care of these children with complex disease and evolving medical status.

Recording diaphragm activity by an oesophageal probe: a new tool to evaluate the recovery of diaphragmatic paralysis

Dear Editor, Insults to the respiratory central nervous system or peripheral nerves can result in respiratory failure leading to prolonged ventilator dependency. Tests currently available to monitor diaphragm function are neither accurate to quantify recovery from diaphragmatic paralysis nor routinely performed at bedside, and predictors of diaphragmatic recovery are lacking. We report two infants with diaphragmatic paralysis secondary to botulism in whom assessment of electrical activity of the diaphragm (EAdi) measured with miniaturized sensors on a feeding tube monitored functional recovery. A 5-month-old patient with botulism was admitted to a pediatric intensive care unit for mechanical ventilation. Eight days after admission, a commercially available feeding tube equipped with sensors (Edi catheter 8 Fr , Maquet Critical Care, Solna, Sweden) was installed, permitting to record EAdi via a Servo-I Ventilator (Maquet Critical Care, Solna, Sweden) using a standardized method [1], and a spontaneous breathing trial (SBT) was performed. The catheter was positioned according to the manufacturer’s recommendations and was verified hourly using the catheter positioning window. This SBT consisted of a 30 min period in pressure support mode with a positive inspiratory pressure of 10 cmH2O and positive end expiratory pressure of 5 cmH2O. The child’s ventilation remained in normal range and passed the trial [2]. During the SBT, chest movements were of small amplitudes and the EAdi waveform was almost flat, with a low EAdi peak (2.9 lV), suggesting that diaphragm weakness was still major, so extubation was delayed. Eight days later, the child had some limb motility and EAdi increased to 4.7 lV during the SBT. The attending physician proceeded to extubation, but the child was reintubated within 3 h due to respiratory muscle weakness. Nine days later, extubation was successful. The second case was a 1-monthold infant with botulism and similar symptoms. EAdi during SBT was done 2 to 3 times per week. We observed a pattern similar to case 1: EAdi was initially very low during SBT (1.0 lV) and increased progressively over 35 days (Fig. 1). The infant was extubated successfully when she had limb motility and her EAdi was 5.9 lV. The monitoring of EAdi is a user friendly bedside tool to measure diaphragm recovery and may help to determine the appropriate timing for extubation, in combination with the evaluation of other extubation criteria (e.g. expiratory capacity). Tests currently used to assess diaphragmatic weakness have significant limitations. Chest radiographs, fluoroscopic imaging, diaphragm ultrasound and static inspiratory pressure measurements are insensitive tests. The ‘‘gold standard’’ techniques, including maximal static transdiaphragmatic pressure and phrenic nerve stimulation [3], are invasive and uncomfortable. Recently, transcranial magnetic stimulation coupled to electromyography has been proposed in predicting the recovery of ventilatory activity [4]. EAdi monitoring can easily be done with a specific feeding tube during daily spontaneous breathing trials [5]. These two cases suggest that this tool, combined with a standardized spontaneous breathing trial, may be helpful for the bedside management of children and adults with bilateral diaphragmatic paresis. Further research is needed to determine the threshold of EAdi correlated with a successful extubation.

Monitoring of children with pediatric acute respiratory distress syndrome: proceedings from the Pediatric Acute Lung Injury Consensus Conference

Objective: To critically review the potential role of monitoring technologies in the management of pediatric acute respiratory distress syndrome, and specifically regarding monitoring of the general condition, respiratory system mechanics, severity scoring parameters, imaging, hemodynamic status, and specific weaning considerations. Design: Consensus conference of experts in pediatric acute lung injury. Methods: A panel of 27 experts met over the course of 2 years to develop a taxonomy to define pediatric acute respiratory distress syndrome and to make recommendations regarding treatment and research priorities. The monitoring subgroup comprised two experts. When published data were lacking a modified Delphi approach, emphasizing strong professional agreement was used. Results: The Pediatric Acute Lung Injury Consensus Conference experts developed and voted on a total of 151 recommendations addressing the topics related to pediatric acute respiratory distress syndrome, 21 of which related to monitoring of a child with pediatric acute respiratory distress syndrome. All 21 recommendations had agreement, with 19 (90%) reaching strong agreement. Conclusions: The Consensus Conference developed pediatric-specific recommendations related to monitoring children with pediatric acute respiratory distress syndrome. These include interpreting monitored values such as tidal volume using predicted body weight, monitoring tidal volume at the end of the endotracheal tube in small children, and continuous monitoring of exhaled carbon dioxide in intubated children with pediatric acute respiratory distress syndrome, among others. These recommendations for monitoring in pediatric acute respiratory distress syndrome are intended to promote optimization and consistency of care for children with pediatric acute respiratory distress syndrome and identify areas of uncertainty requiring further investigation.