Pediatric Acute Respiratory Distress Syndrome Clinical Presentation

Updated: Dec 15, 2021
  • Author: Prashant Purohit, MD; Chief Editor: Timothy E Corden, MD  more...
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Physical Examination

The onset of ARDS can be as rapid as few hours, but it can have a gradual onset with evolution of clinical features over 1 to 5 days. The evolution of clinical signs depends on the type, acuity, and severity of the initial insult. As lungs undergo changes during the first exudative stage of the disease, tachypnea is typically noted as the initial physical finding. Respiratory distress, agitation and hypoxemia could be other initial clinical features at this stage. Crackles may be audible throughout the lung fields, signifying pulmonary edema coinciding with infiltrates on chest radiographs. Concomitant fever may reflect the underlying process causing ARDS (eg, pneumonia, sepsis) or may reflect massive cytokine release. Although these are non-specific features and can be seen with any other respiratory or even systemic illness. Hypoxemia might be evident by high oxygen requirement, higher CPAP or PEEP and elevated alveolar-arterial (A-a) oxygen gradient. A-a gradient can be calculated from the equation as mentioned below for the sea level assuming 100% humidification at the alveolar level. Link the equation.

A-a gradient = PAO2 – PaO2 = {FiO2 (Patm – PH2O) – PaCO2/0.8} – PaO2

                     = {0.6 (760-46) – 40/0.8} – 85

                     = {428.4 – 50} – 85

                     = 293.4 

This is for the patient that was discussed earlier for other calculations, who was on mechanical ventilation with FiO2 0.6, PaO2 of 85, SPO2 of 98% and PCO2 of 40 mm Hg.

Reduction in lung compliance and functional residual capacity is noticed with the development of pulmonary edema. Hypoxemia results from intrapulmonary shunting and ventilation-perfusion mismatch. At this stage, utilization of high PEEP will help in oxygenation by alveolar recruitment. Certain areas of lung still would have maintained normal lung compliance and remain at risk of air leak syndromes from high PEEP. After the initiation of fibro proliferation, lung compliance is further reduced. Benefit of PEEP on oxygenation is less remarkable at this stage. In fact, difficulty in achieving adequate ventilation might be experienced at this stage with resultant hypercarbia and respiratory acidosis. The requirement of mechanical ventilation might be as long as few weeks with overall clinical recovery in months. Pediatric patients have exhibited reduced lung function, broncho reactivity, muscle wasting and weakness for a prolonged period of time after survival from ARDS. [48]