Clinical meaning
Pulmonary surfactant is a complex mixture of phospholipids (90%, primarily DPPC - dipalmitoylphosphatidylcholine) and surfactant proteins (SP-A, SP-B, SP-C, SP-D). Type II pneumocytes begin producing surfactant at 24-28 weeks but adequate amounts not present until 34-36 weeks. Surfactant reduces alveolar surface tension according to LaPlace's Law (P = 2T/r), preventing atelectasis. Without it, high opening pressures are needed, causing barotrauma and oxygen toxicity leading to BPD.
Diagnosis & workup
Diagnostics & workup: - Order CXR (ground-glass opacification with air bronchograms) - Order serial ABGs to monitor oxygenation and ventilation - Calculate a/A ratio and Oxygenation Index (OI = MAP × FiO2 × 100 / PaO2) - Order L/S ratio or PG from amniotic fluid for lung maturity assessment - Order echocardiogram to rule out PDA and assess cardiac function - Order serial CBG/ABG to guide ventilator management - Order head ultrasound for IVH screening in preterm infants - Monitor surfactant protein levels if genetic deficiency suspected