transient tachypnea, TTN, RDS II

This is a newborn nursery diagnosis. It occurs most often in babies born by caesarian section, but can affect babies born vaginally as well. It is caused by excess fluid retained in the lung tissues1 of a baby after birth. It manifests itself as rapid, shallow breathing, with grunting repiratory sounds.

Xray photographs of the lungs reveal a characteristic streaky appearance of the lungs, which are usually fully inflated (as opposed to the uniformly hazy ground glass appearance of the lungs in classic hyaline membrand disease or RDS type I).

The common explanation for this phenomenon is that the lungs are not properly "squeezed out" by passage through the narrow birth canal and thus remain overly "wet." This explanation has a certain ring of plausibility to it, but this explanation is probably a convenient rationalization to hide our ignorance.

In any event, uncomplicated RDS type II runs its course in a few days, as the excess fluid is absorbed into the bloodstream and the lungs dry out.

1The excess fluid is not in the air sacs. The tissues of the lung that occupy the space between the breathing tubes (bronchi and bronchioles) and the air sacs (alveoli) is called the interstitium. This tissue is meant not to accumulate fluid, but rather to stay relatively "dry" and "spongy." Excess fluid in the interstitial tissues makes the lungs stiff (reduced lung "compliance" or elasticity). This is why the baby finds it easier to breathe in a rapid, shallow manner.

There is some recent data to suggest that there is an association between TTN in the newborn period and wheezing and asthma in later childhood. It is not known what the connection might be, but statistically the risk for later wheezing in TTN babies is increased, especially if the mother has a history of asthma. This would not be something to worry about, but simply be aware of the possibilities.

Liem JJ, Huq SL, Ekuma O, et al. Transient tachypnea of the newborn may be an early clinical manifestation of wheezing symptoms. J Pediatrics 2007;151:29-33

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