Current Trends in Pediatric ARDS

Pediatric acute respiratory distress syndrome (PARDS) incidence is reported between 2.95 to 12.8 cases per 100,000 person years,(1,2) which is lower than in adults but remains one of the most challenging form of lung diseases for a Pediatric Intensivist. Application of the adult ARDS definition is limited in pediatrics due to differences in risk factors, etiology, pathophysiology, hard to obtain PaO2 values, and lower levels and variation of PEEP utilization. To address these limitations, to promote early recognition and diagnosis of PARDS, and to improve prognostication and stratification of disease severity, the Pediatric Acute Lung Injury Consensus Conference (PALICC) published the first definition for PARDS in 2015.(3) This definition (Table 1) kept the criteria of onset within seven days of a known clinical insult and the presence of respiratory failure not fully explained by cardiac failure or fluid overload. It eliminated the term acute lung injury, excluded bilateral infiltrate, and stratified severity of PARDS based on the oxygenation deficit as mild, moderate, and severe. Either oxygenation index or the oxygen saturation index (when arterial blood gas is not available) can be used to assess the degree of hypoxemia. Non-invasive ventilation is now included for continuous positive airway pressure of more than 5 cm H2O. Furthermore, PALICC included recommendations for defining PARDS in children with preexisting chronic lung disease, cyanotic congenital heart disease, and left ventricular dysfunction. The PARDS management guidelines are based on very limited pediatric data and are largely based on expert opinions.(3) For ventilatory management, no mode of ventilation is found to be superior, patient-specific tidal volumes per ideal body weight according to disease severity are recommended (3–6 mL/kg for patients with reduced and 5–8 mL/kg for patients with better-preserved compliance). In the absence of transpulmonary pressure measurements, plateau pressure should be limited to 28 cm H2O and 29–32 cm H2O during increased chest wall elastance. Moderately elevated PEEP to 10–15 cm H2O should be titrated in severe PARDS to the observed oxygenation and hemodynamic response. The oxygenation goal for mild PARDS (PEEP < 10) is 92–97% and severe PARDS (PEEP >10) 88–92%, although in some patients, < 88% can be considered with oxygen delivery monitoring. Permissive hypercapnia with a pH of >7.15 is the goal except in severe pulmonary hypertension, intracranial hypertension, select congenital heart lesions, significant ventricular dysfunction with hemodynamic instability, and pregnancy. Recruitment maneuvers by slow incremental and decremental PEEP steps may be used for severe hypoxemia. High-frequency oscillatory ventilation remains as an alternative ventilatory mode for patients with moderate-to-severe PARDS. There is not enough evidence to support the routine use of inhaled nitric oxide, steroids, or prone positioning for PARDS at this time.(3) Since the publication of the new definition, several studies comparing the previous definitions to PALICC suggest that the PALICC definition can not only identify more patients with PARDS but it is also better at risk stratification for mortality.(4,5) Despite decades of research and experience of managing PARDS, there remains a lack of definitive clinical evidence in Pediatrics. Further pediatric research is needed to gain more insight and to improve outcome of PARDS.