Allowing the ventilated adult patient to breathe spontaneously may improve tidal volume (V
) distribution toward the dependent lung regions, reduce shunt fraction, and decrease dead space. It has not ...been studied if these effects under various levels of ventilatory support also occur in children. We sought to explore the effect of level of ventilatory support on V
distribution and end-expiratory lung volume (EELV) in spontaneously breathing ventilated children in the recovery phase of their acute respiratory failure.
This is a secondary analysis of data from a prospective clinical trial comparing 2 different ventilator modes during weaning in mechanically ventilated children < 5 y: CPAP + pressure support ventilation (PSV) and pressure control (PC)/intermittent mandatory ventilation (IMV) + PSV with the mandatory breath rate set at 25% of baseline. Using electrical impedance tomography (EIT), we assessed V
distribution by calculating the center of ventilation. Polynomial functions of the second degree were plotted to evaluate regional lung filling characteristics. Changes in end-expiratory impedance were calculated to assess changes in EELV. Baseline measurements were compared with measurements during CPAP/PSV, PC/IMV + PSV, and during a downward titration of the level of pressure support.
Thirty-five subjects with a median age 4.5 (2.1-12.9) months and a median ventilation time of 4.9 (3.3-6.9) d were studied. The overall median coefficient of variation was 50.1% and not different between CPAP/PSV or PC/synchronized IMV + PSV. Regional filling characteristics of the lung identified a homogeneous V
distribution under all study conditions. Downtapering of the level of PSV resulted in a significant shift of the coefficient of variation toward the dependent lung regions.
Our data showed that allowing ventilated children in the recovery phase of respiratory failure to breathe spontaneously in a continuous spontaneous ventilation mode did not negatively affect V
distribution or EELV.
The underlying pathophysiological pathways how reverse triggering is being caused are not fully understood. Respiratory entrainment may be one of these mechanisms, but both terms are used ...interchangeably. We sought to characterize reverse triggering and the relationship with respiratory entrainment among mechanically ventilated children with and without acute lung injury.
We performed a secondary phyiology analysis of two previously published data sets of invasively mechanically ventilated children < 18 years with and without lung injury mechanically ventilated in a continuous or intermittent mandatory ventilation mode. Ventilator waveforms, electrical activity of the diaphragm measured with surface electromyography and oesophageal tracings were analyzed for entrained and non-entrained reverse triggered breaths.
In total 102 measurements (3110 min) from 67 patients (median age 4.9 1.8 ; 19,1 months) were analyzed. Entrained RT was identified in 12 (12%) and non-entrained RT in 39 (38%) recordings. Breathing variability for entrained RT breaths was lower compared to non-entrained RT breaths. We did not observe breath stacking during entrained RT. Double triggering often occurred during non-entrained RT and led to an increased tidal volume. Patients with respiratory entrainment related RT had a shorter duration of MV and length of PICU stay.
Reverse triggering is not one entity but a clinical spectrum with different mechanisms and consequences.
Not applicable.
The patient's neuro-respiratory drive, measured as electrical activity of the diaphragm (EAdi), quantifies the mechanical load on the respiratory muscles. It correlates with respiratory effort but ...requires a dedicated esophageal catheter. Transcutaneous (surface) monitoring of respiratory muscle electromyographic (sEMG) signals may be considered a suitable alternative to EAdi because of its non-invasive character, with the additional benefit that it allows for simultaneously monitoring of other respiratory muscles. We therefore sought to study the neuro-respiratory drive and timing of inspiratory muscles using sEMG in a cohort of children enrolled in a pediatric ventilation liberation trial. The neuro-mechanical coupling, relating the pressure generated by the inspiratory muscles to the sEMG signals of these muscles, was also calculated.
This is a secondary analysis of data from a randomized cross-over trial in ventilated patients aged < 5 years. sEMG recordings of the diaphragm and parasternal intercostal muscles (ICM), esophageal pressure tracings and ventilator scalars were simultaneously recorded during continuous spontaneous ventilation and pressure controlled-intermittent mandatory ventilation, and at three levels of pressure support. Neuro-respiratory drive, timing of diaphragm and ICM relative to the mechanical ventilator's inspiration and neuro-mechanical coupling were quantified.
Twenty-nine patients were included (median age: 5.9 months). In response to decreasing pressure support, both amplitude of sEMG (diaphragm: p = 0.001 and ICM: p = 0.002) and neuro-mechanical efficiency indices increased (diaphragm: p = 0.05 and ICM: p < 0.001). Poor correlations between neuro-respiratory drive and respiratory effort were found, with R
: 0.088 0.021-0.152.
sEMG allows for the quantification of the electrical activity of the diaphragm and ICM in mechanically ventilated children. Both neuro-respiratory drive and neuro-mechanical efficiency increased in response to lower inspiratory assistance. There was poor correlation between neuro-respiratory drive and respiratory effort.
ClinicalTrials.gov ID NCT05254691. Registered 24 February 2022, registered retrospectively.
Abstract
Background
Recurrent delivery of tidal mechanical energy (ME) inflicts ventilator-induced lung injury (VILI) when stress and strain exceed the limits of tissue tolerance. Mechanical power ...(MP) is the mathematical description of the ME delivered to the respiratory system over time. It is unknown how ME relates to underlying lung pathology and outcome in mechanically ventilated children. We therefore tested the hypothesis that ME per breath with tidal volume (Vt) normalized to bodyweight correlates with underlying lung pathology and to study the effect of resistance on the ME dissipated to the lung.
Methods
We analyzed routinely collected demographic, physiological, and laboratory data from deeply sedated and/or paralyzed children < 18 years with and without lung injury. Patients were stratified into respiratory system mechanic subgroups according to the Pediatric Mechanical Ventilation Consensus Conference (PEMVECC) definition. The association between MP, ME, lung pathology, and duration of mechanical ventilation as a primary outcome measure was analyzed adjusting for confounding variables and effect modifiers. The effect of endotracheal tube diameter (ETT) and airway resistance on energy dissipation to the lung was analyzed in a bench model with different lung compliance settings.
Results
Data of 312 patients with a median age of 7.8 (1.7–44.2) months was analyzed. Age (
p
< 0.001), RR
p
< 0.001), and Vt < 0.001) were independently associated with MPrs. ME but not MP correlated significantly (
p
< 0.001) better with lung pathology. Competing risk regression analysis adjusting for PRISM III 24 h score and PEMVECC stratification showed that ME on day 1 or day 2 of MV but not MP was independently associated with the duration of mechanical ventilation. About 33% of all energy generated by the ventilator was transferred to the lung and highly dependent on lung compliance and airway resistance but not on endotracheal tube size (ETT) during pressure control (PC) ventilation.
Conclusions
ME better related to underlying lung pathology and patient outcome than MP. The delivery of generated energy to the lung was not dependent on ETT size during PC ventilation. Further studies are needed to identify injurious MErs thresholds in ventilated children.
Abstract
Background
Patient–ventilator asynchrony is associated with increased morbidity and mortality. A direct causative relationship between Patient–ventilator asynchrony and adverse clinical ...outcome have yet to be demonstrated. It is hypothesized that during trigger errors excessive pleural pressure swings are generated, contributing to increased work-of-breathing and self-inflicted lung injury. The objective of this study was to determine the additional work-of-breathing and pleural pressure swings caused by trigger errors in mechanically ventilated children.
Methods
Prospective observational study in a tertiary paediatric intensive care unit in an university hospital. Patients ventilated > 24 h and < 18 years old were studied. Patients underwent a 5-min recording of the ventilator flow–time, pressure–time and oesophageal pressure–time scalar. Pressure–time–product calculations were made as a proxy for work-of-breathing. Oesophageal pressure swings, as a surrogate for pleural pressure swings, during trigger errors were determined.
Results
Nine-hundred-and-fifty-nine trigger errors in 28 patients were identified. The additional work-of-breathing caused by trigger errors showed great variability among patients. The more asynchronous breaths were present the higher the work-of-breathing of these breaths. A higher spontaneous breath rate led to a lower amount of trigger errors. Patient–ventilator asynchrony was not associated with prolonged duration of mechanical ventilation or paediatric intensive care stay.
Conclusions
The additional work-of-breathing caused by trigger errors in ventilated children can take up to 30–40% of the total work-of-breathing. Trigger errors were less common in patients breathing spontaneously and those able to generate higher pressure–time–product and pressure swings.
Trial registration
Not applicable.
Abstract
Background
Ventilator liberation is one of the most challenging aspects in patients with respiratory failure. Most patients are weaned through a transition from full to partial respiratory ...support, whereas some advocate using a continuous spontaneous ventilation (CSV). However, there is little scientific evidence supporting the practice of pediatric ventilator liberation, including the timing of onset of and the approach to weaning mode. We sought to explore differences in patient effort between a pressure controlled continuous mode of ventilation (PC-CMV) in this cohort PC assist/control (PC-A/C) with a reduced ventilator rate and CSV, and to study changes in patient effort with decreasing PS.
Methods
In this prospective physiology cross-over study, we randomized children < 5 years to first PC-A/C with a 25% reduction in ventilator rate, or CSV (continuous positive airway pressure CPAP + PS). Patients were then crossed over to the other arm. Patient effort was measured by calculating inspiratory work of breathing (WOB) using the Campbell diagram (WOB
Campbell
), and by pressure–rate-product (PRP) and pressure–time-product (PTP). Respiratory inductance plethysmography (RIP) was used to calculate the phase angle. Measurements were obtained at baseline, during PC-A/C and CPAP + PS, and during decreasing set PS (maximum -6 cmH
2
O).
Results
Thirty-six subjects with a median age of 4.4 (IQR 1.5–11.9) months and median ventilation time of 4.9 (IQR 3.4–7.0) days were included. Nearly all patients (94.4%) were admitted with primary respiratory failure. WOB
Campbell
during baseline 0.67 (IQR 0.38–1.07) Joules/L did not differ between CSV 0.49 (IQR 0.17–0.83) Joules/L or PC-A/C 0.47 (IQR 0.17–1.15) Joules/L. Neither PRP, PTP, ∆Pes nor phase angle was different between the two ventilator modes. Reducing pressure support resulted in a statistically significant increase in patient effort, albeit that these differences were clinically negligible.
Conclusions
Patient effort during pediatric ventilation liberation was not increased when patients were in a CSV mode of ventilation compared to a ventilator mode with a ventilator back-up rate. Reducing the level of PS did not lead to clinically relevant increases in patient effort. These data may aid in a better approach to pediatric ventilation liberation.
Trial registration
clinicaltrials.gov NCT05254691. Registered 24 February 2022
For years, paediatric critical care practitioners used the adult American European Consensus Conference (AECC) and revised Berlin Definition (BD) for acute respiratory distress syndrome (ARDS) to ...study the epidemiology of paediatric ARDS (PARDS). In 2015, the paediatric specific definition, Paediatric Acute Lung Injury Consensus Conference (PALICC) was developed. The use of non-invasive metrics of oxygenation to stratify disease severity were introduced in this definition, although this potentially may lead to a confounding effect of disease severity since it is more common to place indwelling arterial lines in sicker patients. We tested the hypothesis that PALICC outperforms AECC/BD in our high acuity PICU, which employs a liberal use of indwelling arterial lines and high-frequency oscillatory ventilation (HFOV).
We retrospectively collected data from children < 18 years mechanically ventilated for at least 24 h in our tertiary care, university-affiliated paediatric intensive care unit. The primary endpoint was the difference in the number of PARDS cases between AECC/BD and PALICC. Secondary endpoints included mortality and ventilator free days. Performance was assessed by the area under the receiver operating characteristics curve (AUC-ROC).
Data from 909 out of 2433 patients was eligible for analysis. AECC/BD identified 35 (1.4%) patients (mortality 25.7%), whereas PALICC identified 135 (5.5%) patients (mortality 14.1%). All but two patients meeting AECC/Berlin criteria were also identified by PALICC. Almost half of the cohort (45.2%) had mild, 33.3% moderate and 21.5% severe PALICC PARDS at onset. Highest mortality rates were seen in patients with AECC acute lung injury (ALI)/mild Berlin and severe PALICC PARDS. The AUC-ROC for Berlin was the highest 24 h (0.392 0.124-0.659) after onset. PALICC showed the highest AUC-ROC at the same moment however higher than Berlin (0.531 0.345-0.716). Mortality rates were significantly increased in patients with bilateral consolidations (9.3% unilateral vs 26.3% bilateral, p = 0.025).
PALICC identified more new cases PARDS than the AECC/Berlin definition. However, both PALICC and Berlin performed poorly in terms of mortality risk stratification. The presence of bilateral consolidations was associated with a higher mortality rate. Our findings may be considered in future modifications of the PALICC criteria.
Background
Paediatric critical care practitioners often make use of pressure support (PS) to overcome the perceived imposed work of breathing (WOBimp) during an extubation readiness test (ERT). ...However, no paediatric data are available that shows the necessity of adding of pressure support during such tests. We sought to measure the WOBimp during an ERT with and without added pressure support and to study its clinical correlate. This was a prospective study in spontaneously breathing ventilated children < 18 years undergoing ERT. Using tracheal manometry, WOBimp was calculated by integrating the difference between positive end-expiratory pressure (PEEP) and tracheal pressure (Ptrach) over the measured expiratory tidal volume (VTe) under two paired conditions: continuous positive airway pressure (CPAP) with and without PS. Patients with post-extubation upper airway obstruction were excluded.
Results
A total of 112 patients were studied. Median PS during the ERT was 10 cmH
2
O. WOBimp was significantly higher without PS (median 0.27, IQR 0.20–0.50 J/L) than with added PS (median 0.00, IQR 0.00–0.11 J/L). Although there were statistically significant changes in spontaneous breath rate 32 (23–42) vs. 37 (27–46) breaths/min,
p
< 0.001 and higher ET-CO
2
5.90 (5.38–6.65) vs. 6.23 (5.55–6.94) kPa,
p
< 0.001 and expiratory Vt decreased 7.72 (6.66–8.97) vs. 7.08 (5.82–8.08) mL/kg,
p
< 0.001 in the absence of PS, these changes appeared clinically irrelevant since the Comfort B score remained unaffected 12 (10–13) vs. 12 (10–13),
P
= 0.987. Multivariable analysis showed that changes in WOBimp occurred independent of endotracheal tube size.
Conclusions
Withholding PS during ERT does not lead to clinically relevant increases in WOBimp, irrespective of endotracheal tube size.
To map the evidence for ventilation liberation practices in pediatric respiratory failure using the Realist And MEta-narrative Evidence Syntheses: Evolving Standards publication standards.
CINAHL, ...MEDLINE, COCHRANE, and EMBASE. Trial registers included the following: ClinicalTrials.gov, European Union clinical trials register, International Standardized Randomized Controlled Trial Number register.
Abstracts were screened followed by review of full text. Articles published in English language incorporating a heterogeneous population of both infants and older children were assessed.
None.
Weaning can be considered as the process by which positive pressure is decreased and the patient becomes increasingly responsible for generating the energy necessary for effective gas exchange. With the growing use of noninvasive respiratory support, extubation can lie in the middle of the weaning process if some additional positive pressure is used after extubation, while for some extubation may constitute the end of weaning. Testing for extubation readiness is a key component of the weaning process as it allows the critical care practitioner to assess the capability and endurance of the patient's respiratory system to resume unassisted ventilation. Spontaneous breathing trials (SBTs) are often seen as extubation readiness testing (ERT), but the SBT is used to determine if the patient can maintain adequate spontaneous ventilation with minimal ventilatory support, whereas ERT implies the patient is ready for extubation.
Current literature suggests using a structured approach that includes a daily assessment of patient's readiness to extubate may reduce total ventilation time. Increasing evidence indicates that such daily assessments needs to include SBTs without added pressure support. Measures of elevated load as well as measures of impaired respiratory muscle capacity are independently associated with extubation failure in children, indicating that these should also be assessed as part of ERT.
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