Transient tachypnoea of the newborn: overview of neonatal wet lung syndrome

By Cristiano Antonino On Jun 4, 2022

Transient tachypnoea of the newborn (also called ‘transient neonatal tachypnoea’ or ‘neonatal wet lung syndrome’) is a respiratory disorder of the newborn caused by delayed reabsorption of fetal lung fluid that can lead to transient respiratory distress and, in severe cases, death of the newborn due to respiratory failure

The incidence of transient tachypnoea in the neonate is about 1%

Transient tachypnoea of the neonate is caused by a delay in reabsorption of fetal lung fluid.

Pathophysiology of transient tachypnoea of the neonate (neonatal wet lung syndrome)

The delay in reabsorption of lung fluid is partly determined by the immaturity of the Na (sodium) channels in the lung epithelial cells: these channels are responsible for the uptake of Na (and thus water) from the alveoli and – if they are immature – may not be able to perform this task and result in poor reabsorption of the foetal lung fluid.

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Risk factors for transient tachypnoea in the newborn are:

premature birth
gestational age of 28 weeks or less;
low birth weight (less than 1500 grams, i.e. 1.5 kg)
male gender;
neonates with respiratory depression and delayed fetal lung fluid clearance;
low growth parameters in newborns (length, weight and head circumference);
low Apgar index;
macrosomia;
bronchial asthma;
diabetic father;
diabetic mother;
mother malnourished by default
mother with multiple pregnancies;
mother who abuses alcohol and/or takes drugs;
persistent pulmonary hypertension;
term babies delivered by elective caesarean section without labour;
siblings born prematurely and/or with transient tachypnoea of the newborn and/or with cardiac malformations.

The symptoms and signs of transient tachypnoea of the newborn are

tachypnoea (rapid breathing);
cyanosis (bluish colour of the skin);
dyspnoea (difficulty breathing);
grunting;
enlargement of the nasal fins (dilation of the nostrils);
intracostal and subcostal retractions;
noisy breathing.

Diagnosis

The diagnosis of transient tachypnoea in the newborn is suspected on objective examination if there are signs of respiratory distress shortly after birth.

The diagnosis of certainty is reached by a chest X-ray, which shows overexpanded lungs with reinforcement of the perilymph pattern, a hirsute appearance of the cardiac margins, a clear pulmonary periphery and fluid in the pulmonary scissors.

CBC, blood cultures and haemogasanalysis (showing hypoxaemia) may also be performed.

Differential diagnosis

The differential diagnosis arises in relation to other conditions that lead to neonatal respiratory distress, such as meconium aspiration syndrome.

The latter, however, tends to occur in the case of post-term delivery (gestation of more than 40 weeks) whereas, as we have seen, transient tachypnoea of the new-born tends to occur mainly in the case of pre-term delivery.

The differential diagnosis also arises with regard to pneumonia, neonatal respiratory distress syndrome and sepsis.

The treatment of transient neonatal tachypnoea consists mainly of oxygen therapy (administration of oxygen) with a stretcher, with the baby under close observation

Rarely, very premature infants and/or those with neurological depression at birth or other respiratory problems (e.g. congenital airway malformation respiratory distress syndrome) require continuous positive pressure ventilation.

Only in the most severe cases should the infant be intubated and mechanical ventilation be performed.

If the initial results are indeterminate or there are signs indicating a bacterial infection, antibiotics (e.g. ampicillin and gentamicin) are administered to the infant while waiting for culture results to arrive from the laboratory.

Duration

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In most cases, if the medical intervention was rapid and the baby reacted well to the O2 therapy, a few days after birth (usually 2 – 4 days) the respiratory situation usually normalises without any sequelae.

The prognosis of transient tachypnoea in the newborn is generally good

Factors that may increase the severity and worsen the prognosis are:

very premature birth
gestational age less than 28 weeks;
low birth weight (less than 1500 grams, i.e. 1.5 kg);
untimely intervention by medical personnel;
low Apgar index;
respiratory distress syndrome;
sepsis;
pneumonia;
damage to the nervous system;
endocranial complications related to hypoxaemia, hypercapnia, hypotension, blood pressure fluctuations and low cerebral perfusion;
endocranial haemorrhage;
presence of other congenital or acquired pulmonary diseases, e.g:
airway malformations,
persistent pulmonary hypertension,
pulmonary agenesis,
meconium aspiration syndrome,
pulmonary hypoplasia,
pulmonary aplasia,
broncho-pulmonary dysplasia,
hypertensive pneumothorax;
presence of other congenital systemic diseases (e.g. cardiac malformations, typically a pervious Botallo’s duct).