Topics Discussed: pulmonology and respiratory medicine; transitory tachypnea of newborn.
Excerpt:"Definition. Transient tachypnea of the newborn (TTN) is also known as wet lung or type II respiratory distress syndrome (RDS). It is a benign disease of near-term, term, or large premature infants who have respiratory distress shortly after delivery that usually resolves within 35 days.
Incidence. The incidence of TTN is ~12% of all newborns.
Pathophysiology. Its true cause is unknown, but three factors are involved.
- Delayed resorption of fetal lung fluid. TTN is thought to occur because of delayed resorption of fetal lung fluid from the pulmonary lymphatic system. The increased fluid volume causes a reduction in lung compliance and increased airway resistance. This results in tachypnea and retractions. Infants delivered by elective cesarean delivery are at risk because of lack of the normal vaginal thoracic squeeze, which forces lung fluid out.
- Pulmonary immaturity. One study noted that a mild degree of pulmonary immaturity is a central factor in the cause of TTN. The authors found a mature L-S ratio but negative phosphatidylglycerol (the presence of phosphatidylglycerol indicates completed lung maturation) in infants with TTN. Infants who were closer to 36 weeks' gestation than to 38 weeks had an increased risk of TTN.
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