Recommendations for mechanical ventilation of critically ill children

12.06.2018
Author: Süha Demirakca, Reviewer: Paul Garbarini

Common clinical practice in pediatric mechanical ventilation is largely based on personal experience or what has been adopted from adult and neonatal studies. There is a fundamental lack of clinical evidence to support the daily practice of pediatric mechanical ventilation, due in part to the extensive variability in lung size, maturity and range of acute and chronic respiratory conditions existing in all age groups of children.

Take-away messages

  • There is a fundamental lack of clinical evidence supporting the daily practice of pediatric mechanical ventilation
  • The European Society for Pediatric and Neonatal Intensive Care initiated a consensus conference of experts, who subsequently made a total of 152 recommendations
  • A crucial element of these recommendations is the implementation of a stratification of respiratory conditions based on airway mechanics (normal, restrictive, obstructive and mixed disease)
  • Ventilator settings at the bedside should be guided by the respiratory mechanics of the underlying lung conditions

The European Society for Pediatric and Neonatal Intensive Care initiated a consensus conference of experts to provide recommendations for pediatric mechanical ventilation. In total, 152 recommendations were made with respect to the following topics:

(1) general recommendations, (2) monitoring, (3) targets for oxygenation and ventilation, (4) supportive measures, (5) weaning and extubation readiness, (6) normal lungs, (7) obstructive diseases, (8) restrictive diseases, (9) mixed diseases, (10) chronically ventilated patients, (11) cardiac patients and (12) lung hypoplasia syndromes.

The panel made the decision to keep the guideline descriptive, rather than using the GRADE system to rate the recommendations’ strength. All the recommendations discussed here were labelled with strong agreement.

In this article, we will focus on the aspects related to setting the ventilator for invasive pediatric mechanical ventilation and setting targets for oxygenation and ventilation in acute respiratory care. A crucial element of these recommendations is the implementation of a stratification of respiratory conditions based on airway mechanics (normal, restrictive, obstructive and mixed disease), which includes pathophysiological considerations in the absence of clinical study data.

Maintaining spontaneous breathing

The panel recommends that all children on respiratory support should preferably breathe spontaneously, with the exception of the most severely ill children with obstructive airway, restrictive or mixed disease requiring very high ventilator settings and intermittent neuromuscular blockade. In these cases, controlled mechanical ventilation should be preferred, as there is a need for continuous sedation and/or muscle relaxants. In the presence of cardiac dysfunction, sedation and relaxation should be used with caution.

Triggering

While the effects of patient-ventilator asynchrony or interventions such as flow cycling on patient outcomes are not clear, improved patient-ventilator synchrony has been shown to impact positively on patient comfort.

Inspiratory time and frequency

The panel recommends setting the inspiratory time and respiratory rate according to the respiratory system mechanics and disease condition. In restrictive lung disease, a higher respiratory rate should be used to compensate for low tidal volumes and to maintain minute ventilation. The time constant of the respiratory system is an important parameter in this context. At the bedside, the panel suggests avoiding flow end-inspiratory or expiratory flow interruption, the latter of which may cause air-trapping.

Setting the pressure

If transpulmonary pressure measurement is not possible, the panel recommends limiting the plateau pressure (Pplat) to ≤ 28 cmH2O, or ≤ 29–32 cmH2O if the chest wall elastance is increased in the case of restrictive lung disease, mixed disease and children with congenital/chronic disorders. In obstructive airway disease, Pplat should be limited to ≤ 30 cmH2O. Measuring transpulmonary pressure (Ptp) instead of airway pressure (Paw) provides a better indication of lung strain in (severe) lung injury, particularly where there is increased chest wall elastance. The panel recommends maintaining delta pressure (i.e., the difference between end-inspiratory and end-expiratory pressure) at less than 10 cmH2O if there is no lung pathology. There is no data on which to base a recommendation for any acceptable delta pressure in restrictive, obstructive airway or mixed disease. For children with reduced lung volumes, the driving pressure at zero flow (Vt/Crs) may dictate the optimal tidal volume (Vt). In adults, driving pressure (ΔP = Vt/Crs) has been shown to best stratify the risk for mortality with ARDS.

Setting tidal volume

There is no data to recommend the optimal Vt in restrictive, obstructive airway or mixed disease. The panel recommends targeting a physiological Vt and avoiding Vt of greater than 10 ml/kg ideal bodyweight. In children with lung hypoplasia syndromes, the optimal Vt may be lower than the physiological Vt due to the lower lung volumes.

Setting PEEP

The panel recommends PEEP to prevent alveolar collapse. Physiological data in children without lung injury suggests setting PEEP at 3–5 cmH2O, however in severe disease, high PEEP may be needed. PEEP should always be set with a view to achieving the optimal balance between hemodynamics and oxygenation, and PEEP titration may be attempted to help improve oxygenation. However, there is no defined method for setting the best PEEP. Moderate PEEP is sufficient when there is no lung pathology, but higher PEEP may be necessary in more severe disease to restore end-expiratory lung volume and improve respiratory system compliance (Crs), if it does not impair hemodynamics. However, there is no data that compares low vs. high PEEP in severe lung injury, nor is it clear how to set PEEP or whether markers such as PaO2 or quasi-static Crs predict the best PEEP. In obstructive airway or mixed disease, assessment of intrinsic PEEP and Pplat may guide setting external PEEP in children with air-trapping, who are mechanically ventilated and sedated. A balance needs to be found between alveolar recruitment and alveolar overdistension. The panel recommends using high PEEP to stabilize the airways in ventilated children with trachea- and/or bronchomalacia. Careful titration of PEEP is needed to avoid cardiovascular compromise. Observational data suggested reduced respiratory efforts with PEEP or CPAP in children with upper airway collapse.

Targets for oxygenation

In children without lung injury or extra-pulmonary manifestations, SpO2 of greater than 95% at room air should be expected. The panel recommends adhering to the PALICC guidelines for PARDS (i.e., SpO2 92%–97% when PEEP < 10 cmH2O and 88%–92% when PEEP ≥ 10). In children with cardiorespiratory failure, oxygen therapy should be titrated, balancing pulmonary disease against the underlying cardiac disorder, as well as in some conditions (e.g., single ventricle physiology) balancing pulmonary versus systemic blood flow. It may be necessary to increase FiO2 up to 1.0 in the case of a life-threatening acute pulmonary hypertension crisis. In healthy children breathing room air, SpO2 of greater than 95% and PaO2 between 80 and 100 mmHg should be expected. In cardiac children, in those children with or at risk of lung injury, or in children with pulmonary hypertension, the target SpO2 depends on the type and severity of lesions. PALICC proposed SpO2 of between 92% and 97% when PEEP was lower than 10 cmH2O, and 88%–92% for PEEP ≥ 10 cmH2O in non-cardiac PARDS. There is no data reporting the safety and necessity of a liberal or restrictive oxygen therapy, but as a rule of thumb, the lowest FiO2 should be targeted.

Targets of ventilation

The panel recommends achieving normal CO2 levels in children with normal lungs. For acute pulmonary children, higher levels of CO2 may be accepted unless specific disease conditions dictate otherwise. Further recommendations are permissive hypercapnia targeting a pH > 7.20 and maintaining a normal pH in children at risk of pulmonary hypertension. Titration of pH may be used as a non-pharmacological tool to modify pulmonary vascular resistance for specific disease conditions. In healthy children, normal CO2 levels (i.e. 35–45 mmHg) should be expected. Attempts to normalize mild hypercapnia by increasing ventilator settings may be detrimental. Normal pH and PCO2 should be targeted in severe traumatic brain injury and pulmonary hypertension.

Conclusion

The consensus clearly reflects the virtual absence of scientific evidence to support the current approach to pediatric mechanical ventilation. The huge gaps evident in our knowledge of this subject should motivate all those active in the field of pediatric ventilation to join forces in an effort to fill them. This consensus is an initial step towards improving the application of mechanical ventilation in critically ill children.

One of the important considerations contained in these recommendations is that the ventilator settings at the bedside should be guided by the respiratory mechanics of the underlying lung conditions. All Hamilton Medical ventilators measure pressure and flow directly at the proximal end (patient side) of the breathing circuit and thus provide very precise values for the properties of respiratory mechanics such as compliance, resistance, and the time constant. This high level of sensitivity and precision is particularly important when ventilating children, and better enables the clinician to select the ventilator settings as recommended in this guideline.

References

  • Kneyber MCJ et al. Recommendations for mechanical ventilation of critically ill children from the Paediatric Mechanical Ventilation Consensus Conference (PEMVECC). Intensive Care Med (2017) 43:1764–1780.
  • Rimensberger PC et al.  Pediatric Acute Lung Injury Consensus Conference G Ventilatory support in children with pediatric acute respiratory distress syndrome: proceedings from the Pediatric Acute Lung Injury Consensus Conference. Pediatr Crit Care Med (2015) 16:S51–S60

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pediatrics, airway mechanics, respiratory system, oxygenation, targets, inspiratory time, frequency, pressure, tidal volume, PEEP, guideline
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Date of Printing: 10.12.2018
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