What is Broncho-Pulmonary Dysplasia (BPD) or Chronic Lung Disease?
BPD is a condition which can occur where babies have needed support from a ventilator. Their lungs remain stiff, and a chest X-ray shows up changes characteristic of BPD. If this is the case, the baby may need to stay on a ventilator, or on oxygen, for longer – weeks, or (rarely) even months.
Premature babies may need help from a ventilator if:
- their immature lungs are too stiff to work properly, this is called ‘Respiratory Distress Syndrome’; and/or
- their brain is not yet ready to control their breathing to keep it regular (recurrent apnoea).
Given time, both these conditions improve naturally, provided the baby is kept healthy on a ventilator meanwhile. Most babies can be taken off the ventilator and off oxygen as soon as these problems have resolved themselves.
What happens to the lungs to cause BPD? The membrane lining a baby’s lungs is very delicate. If this membrane is damaged, the result can be inflammation, followed by the formation of areas of fibrous tissue (something similar to scar tissue) in the lungs. As a result, the lungs become stiffer than normal.
Some healthy air sacs in the lungs will remain stretchy, and able to take in more air than the damaged, stiff air sacs. This is what gives the patchy X-ray characteristic of BPD. As the baby recovers, healthy tissue gradually replaces the fibrous tissue, and the X-ray will return to normal.
How is BPD diagnosed?
BPD is usually diagnosed where:
- a baby still needs oxygen after 28 days; and
- a chest X-ray shows up the patchy appearance (described above) typical of BPD.
If the baby still needs oxygen, but does not have the typical X-ray, it is likely that the baby has Chronic Lung Disease rather than BPD.
Which babies get BPD?
Successful ventilator therapy for premature babies started in the 1960s, and BPD was initially very common. Since then, techniques have been refined, and BPD is rare in moderately premature babies who need only a few days on a ventilator. Very premature babies of less than 28 weeks are still prone to developing BPD. This is because:
- ventilators place mechanical stresses on the lungs which are particularly tiny and delicate; and
- being so premature, they need to spend longer on a ventilator than a baby born closer to full term.
Although the majority of premature babies are now treated with surfactant to reduce the severity of early breathing problems, this has had little effect on reducing BPD.
What causes BPD?
It is not clear why some babies born after the same length of pregnancy, and treated with the same amount of ventilation and oxygen, develop BPD while others do not.
When a ventilator blows air into a baby’s lungs, mechanical breathing puts a different kind of pressure on the baby’s lungs to the kind of pressure that exists when babies breathe alone. Modern ventilators normally allow these effects to be kept to a minimum, and doctors and nurses will do all they can to use the lowest levels of ventilation and oxygen on which the baby can manage.
Sometimes a baby with severe breathing problems (respiratory distress) will need high ventilator pressures and high oxygen levels. Chest infections may also be a factor; again, very premature babies are the most likely to develop infections. (Don’t worry, in these circumstances, ‘infection’ doesn’t mean the everyday coughs and colds parents or other children have. The use of the word ‘infection’ here is about germs which would have no effect on a healthy adult, but could add to the problems of a premature baby on a ventilator.)
How does BPD affect the baby?
Babies with BPD have to work harder to get air into their stiffer lungs. This may mean a baby needs to stay on a ventilator, and the baby’s chest may pull in as they breathe. When taken off the ventilator the baby may easily become tired, especially during feeds (which may need to be given by a tube for longer than usual). Even after the ventilator is no longer being used, it is still harder for oxygen to get across the membrane lining the lungs, and into the baby’s blood stream. This is why babies with BPD usually need to be kept on oxygen. When babies first come off oxygen, they may still need it during feeding. This prevents the slightly blue tinge to the skin which results from too little oxygen.
Can BPD be prevented?
No, but a lot can be done to reduce it. Babies who need to be on a ventilator will be regularly monitored by means of blood tests and something called a ‘skin electrode’, which gives a constant record of the level of oxygen in the baby’s blood. Some research work is being done on the value of Vitamin E (yet to show any definite benefit) and Vitamin A (encouraging, but more trials are needed to prove whether or not this will be useful). Research work can seem frustratingly slow, but it must be carried out with great care to ensure that possible new treatments do not produce unwanted side effects. This is especially true of any treatment which could be recommended for routine use in all premature babies, just to prevent a small number of them developing BPD.
How is BPD treated?
Treatment aims to reduce ventilation and oxygen very gradually, as the baby’ s lungs improve. Sometimes a baby may need a medicine which makes them pass more urine (this is called a ‘diuretic’) to remove any extra fluid from the lungs. Steroid treatment may also be given to try and speed up the healing process in the lungs. Usually a baby’s oxygen needs will steadily come down, and oxygen can be stopped before the baby is ready to go home. Recovery is sometimes very slow, and the consultant may occasionally allow a baby to go home with an oxygen supply, as long as:
- the baby is otherwise well; and
- there is lots of extra skilled help available, such as a visiting nurse from the neonatal unit.
To give oxygen, a little tube is placed just at the baby’s nostrils. Oxygen can then be supplied from cylinders, or by means of a special machine which concentrates the oxygen in ordinary air.How does BPD affect the baby later on?
When the baby first comes home, ordinary coughs and colds may make them chestier or more wheezy. Re-admission to hospital, or a few days on a ventilator, may sometimes be needed. As the baby gets older and the lungs continue to heal, this will become less of a problem. Babies with BPD are often slower to gain weight, but usually catch up over a period of time. If they were very small at birth, or had a lot of lung problems, they may remain slightly shorter and lighter than other children of their age. Eventually they should be just as healthy as other children, although small changes may remain on the X-rays, or show up on detailed breathing tests. BPD does not in itself affect a child’s development or learning ability. Where a baby has had a lot of other problems, extra help may be of benefit; the pediatrician will be able to give you advice.