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 3–5 days.
Incidence. The incidence of TTN is ~1–2% 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.
Mild surfactant deficiency. One hypothesis is that TTN may represent a mild surfactant deficiency in these infants.
Elective cesarean delivery without preceding labor (especially with gestational age <38 weeks).
Excessive maternal sedation.
Negative amniotic fluid phosphatidylglycerol.
Fluid overload to the mother, especially with oxytocin infusion.
Delayed clamping of the umbilical cord. Optimal time is 45 s.
Infant of a diabetic mother.
Prematurity (can occur but is less frequent).
Infant of drug-dependent mother (narcotics).
Very low birthweight neonates.
Exposure to B-mimetic agents.
Clinical presentation. The infant is usually near term, term, or large and premature and shortly after delivery has tachypnea (>60 breaths/min and can be up to 100–120 breaths/min). The infant may also have grunting, nasal flaring, rib retraction, and varying degrees of cyanosis. The infant often appears to have the classic "barrel chest" secondary to the increased anteroposterior diameter. There are usually no signs of sepsis. Some infants may have edema and a mild ileus on physical examination. One can also see tachycardia with usually a normal blood pressure.
Prenatal testing. A mature L-S ratio with the presence of phosphatidylglycerol in the amniotic fluid may help rule out HMD.
Arterial blood gas on room air shows some degree of mild hypoxia. Hypocarbia is usually present. Hypercarbia, if it exists, is usually mild (PCO2 >55 mm Hg). Extreme hypercarbia is rare and, if present, another diagnosis should be considered.
Complete blood cell count with differential is normal in TTN but should be obtained if one is considering an infectious process. The hematocrit will also rule out polycythemia.
Urine and serum antigen test may help rule out certain bacterial infections.
Plasma endothelin-1 levels (ET-1). One study revealed that plasma ET-1 ...
Log In to View More
If you don't have a subscription, please view our individual subscription options below to find out how you can gain access to this content.
Want remote access to your institution's subscription?
Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.
If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.
AccessPediatrics Full Site: One-Year Subscription
Connect to the full suite of AccessPediatrics content and resources including 20+ textbooks such as Rudolph’s Pediatrics and The Pediatric Practice series, high-quality procedural videos, images, and animations, interactive board review, an integrated pediatric drug database, and more.
Pay Per View: Timed Access to all of AccessPediatrics
24 Hour Subscription $34.95
48 Hour Subscription $54.95
Pop-up div Successfully Displayed
This div only appears when the trigger link is hovered over.
Otherwise it is hidden from view.