This article focuses on the respiratory management and monitoring of pediatric acute lung injury (ALI) as a specific cause for respiratory failure. Definitive, randomized, controlled trials in pediatrics to guide optimal ventilatory management are few. The only adjunct therapy that has been proved to improve clinical outcome is low tidal volume ventilation, but only in adult patients. Careful monitoring of the patient’s respiratory status with airway graphic analysis and capnography can be helpful. Definitive data are needed in the pediatric population to assist in the care of infants, children, and adolescents with ALI to improve survival and functional outcome.
Key points
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Infants and young children are particularly prone to acute respiratory failure because of multiple physiologic factors including small airways (both natural and artificial), weak and ineffective cough clearance, high chest wall compliance, and low diaphragmatic efficiency.
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A key point in the management of the patient with acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is that increased oxygenation does not correlate with improved outcome, which has been shown in studies with low tidal volume ventilation, inhaled nitric oxide, and prone positioning.
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Low tidal volume ventilation in the adult population with 6 mL/kg ideal body weight is the only approach for ALI that has been shown to reduce mortality.
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Although various modes of ventilation are currently used in clinical practice, to date, no data exist to determine the mode that provides the greatest benefit and the least risk to an individual patient, including those with ALI/ARDS.
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Airway graphic analysis and capnography may be useful monitoring tools to assist with optimal ventilatory management, including optimizing patient-ventilator interactions.
Introduction
Acute respiratory failure accounts for more than half of the admissions to pediatric critical care units and is a major cause of morbidity and mortality. Because the causes of acute respiratory failure in the pediatric population are diverse, this article focuses on the respiratory management and monitoring of pediatric acute lung injury (ALI) as a specific cause for respiratory failure. It should be noted from the start that definitive, randomized, controlled trials in pediatrics to guide the intensivist in the optimal ventilatory approach for an individual infant or child with acute respiratory failure and ALI are lacking.
Because much of the respiratory management for this critically ill pediatric population is influenced by data from adult patients, it must be stressed that children are not simply small adults, and, similarly, infants are not simply small adolescents. It is important to stress the basic physiologic differences between these populations. Infants and young children are particularly prone to develop acute respiratory failure because of multiple physiologic factors. Overall, from a respiratory perspective, younger children have smaller airways (both natural and artificial), weaker and less effective cough clearance, greater chest wall compliance, decreased diaphragmatic efficiency, and thus are at a higher risk for airway occlusion.
More specifically, younger patients have reduced elastic alveolar recoil, which can result in increased collapse, especially in the presence of decreased pulmonary compliance. In addition, they have fewer alveoli and collateral ventilation channels to allow ventilation distal to obstructed airways. An infant’s chest wall has greater compliance, making it more difficult to generate a significant negative intrathoracic pressure in the presence of decreased lung compliance. The weaker cartilaginous airway support in infants and young children may lead to dynamic compression (and subsequent airway obstruction) in conditions associated with high expiratory flow rates and increased airway resistance, such as bronchiolitis and asthma. The pediatric airway is also significantly narrower than the adult airway, thus contributing to the development of increased airway resistance and, potentially, secretion-induced obstruction. Despite these potential disadvantages of the pediatric pulmonary system, the progression of acute respiratory failure to acute respiratory distress syndrome (ARDS) is less likely to occur than in adults.
In contrast with the 1994 American-European Consensus Conference definition of ALI and ARDS, the 2011 Berlin Definition ( Table 1 ) specifies the timeframe for the development of ARDS, better defines the nature of infiltrates on chest radiographs, incorporates positive end-expiratory pressure (PEEP) in the definition of the severity of hypoxemia, minimizes the need for invasive pulmonary artery measurements in the presence of cardiac risk factors, and integrates ALI into a subgroup of mild ARDS. A comprehensive pediatric ALI consensus initiative is in progress under the leadership of the Pediatric Acute Lung Injury and Sepsis Investigator (PALISI) Network.
