Pediatric ARDS Dr Abhijeet DeshmukhDNB pediatrics, Fellow PICU & NICU
IntroductionALI and ARDS are common causes of acute hypoxemic respiratory failure in children.In 1967, Ashbaugh and colleagues described a syndrome of tachypnea, hypoxia, and decreased pulmonary compliance in a series of 11 adults and one child with respiratory failure.
Adult respiratory distress syndrome - OLD
Acute respiratory distress syndrome - NEW
DefinitionAmerican- European Consensus Conference definition of ARDS. (1924) Clinical feature Criteria Timing Acute onsetChest Xray Bilateral infiltratesOxygenation Severe hypoxia on Oxygen therapyALI PaO2 /FiO2 5-7days) abnormal lung increases so PEEP is less effective, PaCo2 increases. Fibroproliferative phase slow recovery & ventilator dependency.Resolution phase gradual recovery of hypoxemia, compliance, X ray resolution
ManagementControl of underlying disease/infection AntibioticsRespiratory support :Basic ventilation strategies : Goal maintain adequate oxygenation, minimize VILI, Lung protective strategies Avoid regional overinflation (Baby lung concept)Avoid repeated opening/closing of alveoli (Open lung strategy)Permissive hypercapniaPermissive Hypoxemia
Baby Lung concept : In most patients of ARDS, normally aerated tissue has dimension of 5-6 year old child (300-500gm aerated tissue)Compliance is linearly related to baby lung quality i.e ARDS lung is not only stiff but also small with nearly normal intrinsic elasticity in early phasesThis concept provides rationale for gentle ventilation d/t risk of VILI (at TV >8 ml/kg)
Initiation of VentilationARDS Net trial RCT 861 adult ptTraditional ventilation (Vt -12ml/kg & Ppeak 50cmH2O) Vs Lung protective ventilation (Tv 6,l/kg & Ppeak - < 30cm H2O)Result - Reduced mortality (31% vs 39.5), more vent free days, lower end organ complications.
Initial Ventilator settingsNIV in very early and mild ARDSMode PRVC>PCV>VCV (HFOV when indicated)TV : 7.45) Decrease vent rate if possible
High FiO2 Cellular toxicity, reabsorption atelectasis so keep 60%Failure to improve oxygenation index within 24-48hrsNon responders to HFOV have high mortality.
Surfactant:RCTs and retrospective studies : rapid and sustained improvement in oxygenation, faster weaning, shorter ICU stay but no difference in mortality.
NOUseful in Pulmonary HT in ARDSImproves short term oxygenation in ARDSLittle impact on long term oxygenation and mortality
ECMOTo support oxygenation while lung healing takes placeRetrospective studies survival in critically ill ARDS pts
Noninvasive Support Ventilation Management.(PARDS)NPPV - reduce atelectasis, and potentially unloads fatigued respiratory muscles, preserving the child's natural airway and airway clearance mechanisms. avoids complications of invasive therapies as well as the need for sedation or muscle relaxationNPPV provides a continuous level of positive expiratory pressure - maintains small airway patency, increase end-expiratory lung volumes, and improve pulmonary compliance, reducing the change in alveolar pressure needed to initiate inspiration. With bilevel support, the additional inspiratory pressure can help raise tidal volumes and support fatigued respiratory muscles - improve work of breathing, dyspnea, and gas exchange until the underlying disease process improves.
NPPV be considered early in disease in children at risk for PARDS to improve gas exchange, decrease work of breathing, and potentially avoid complications of invasive ventilationchildren with immunodeficiency more benefitnot recommended for children with severe disease
NIPPV for the Treatment of ARDS -studies
Children with more severe PARDS, however, are significantly more likely to require intubation despite the use of NPPV. the median frequency of NPPV failure in those children with more mild PARDS was 21%
Role of High-flow Nasal Cannula (PARDS)
provides improved oxygenation and reduced dead space by "washing out" of nasopharyngeal CO2, thereby increasing effective ventilation. HFNC generates a modest degree of positive pressure, thereby reducing upper airways resistance and reducing work of breathing. level of positive pressure generated by currently available HFNC systems is unknown, but it is thought to be less than that provided by NPPV.
Approach to DiagnosisEssential Laboratory Tests ABG - PaO2 and PaO2/FiO2 ratio.CXRAcute progressive hypoxemic respiratory failuare.Occasionaly 2DEcho and CT ChestAdditional tests CBC, Lactate, bld c/s, ET secretion C/S, S. ElectrolytesValuable test in severe hypoxemia ScvO2Noninvasive monitoring of systemic oxygenation SPO2 and End tidal CO2 capnography.
Summary Management strategy of ARDS