Neonatology is not a big part of the undergraduate paediatric curriculum. What
appears below should give you and idea of the conditions involved and allow
you to 'bluff your way'.
A neonate is a baby less than 28 days old.
A number of different pathologies can cause respiratory distress in the newborn.
Features of this distress include:
- tachypnoea (>60 breaths/minute)
- subcostal and sternal recession (the soft bones of the newborn's ribcage
are deformed with increased work of breathing) and tracheal tug
- grunting (attempt to maintain Positive End Expiratory Pressure [PEEP] and
thereby prevent lung collapse at expiration)
- nasal flaring
- low saturations
- apnoea (immature brain control of respiration)
Hyaline Membrane Disease (HMD) is the pathological finding in the lungs
of newborn premature babies. The clinical picture it produces is called 'Respiratory
Distress Syndrome' (RDS).
The condition is caused by immaturity of the lungs, especially lack of surfactant
production. The absence of surfactant, which normally reduces the surface tension
in the lungs, leads to collapse. It can occur in term infants, especially infants
of diabetic mothers, though this is rare. As well as lacking surfactant the
lungs of premature babies are underdeveloped. Alveoli only start to form at
about 24 weeks' gestation and at this stage are thick walled and poorly adapted
for gas exchange. As the baby matures so do the lungs with increased numbers
and maturity of the alveoli. (This development actually continues until the
child is about seven years old).
It is lung maturity that usually limits resuscitation of very premature infants.
Steroids given to mother up to 48 hours before delivery help to mature the lungs
by 'switching on' surfactant production. After delivery surfactant can be given
to babies with RDS.
Bronchopulmonary Dysplasia (BPD) is the sequel of hyaline membrane disease.
It is defined as an oxygen requirement beyond 36 weeks gestation (previously
an oxygen requirement at 28 days of age). It results from damage to the developing
lung caused by HMD and ventilation. Babies with BPD can require oxygen for well
over a year after delivery. Failure to provide adequate oxygen can lead to pulmonary
hypertension and death. Steroids are sometimes used to ameliorate the condition.
Transient Tachypnoea of the Newborn (TTN) is caused by retained lung
fluid after delivery. During a normal delivery the fluid in a baby's lungs is
squeezed out through the mouth and reabsorbed into the lungs. If this fails
to happen (e.g. if the baby is delivered by routine caesarean section) the lung
fluid can be retained and can cause respiratory distress. Treatment is rarely
required but the importance of TTN lies in its differential diagnoses (i.e.
sepsis, RDS, pneumothorax, lung malformation).
Meconium Aspiration can occur if a baby has a bowel action (passes meconium)
as a result of stress during delivery. Foetal breathing movement then draw the
meconium into the lungs where it can cause a inflammation (pneumonitis). Babies
with meconium aspiration syndrome can be very ill though much of this may be
due to the distress which caused the passage of meconium during labour. Despite
this aspiration of meconium in its own right can result in significant morbidity.
Pneumothorax can occur spontaneously after delivery (possibly in up
to 5% of deliveries) or be caused by too high an inflation pressure being used
to expand the lungs if resuscitation is required.
Lung Malformations (diaphragmatic hernia, sequestrated lobe) congenital
heart disease (CHD) are rare but important causes of respira